Showing 1–50 of 95 results for author: Spiniello, C

CORN -- Chronometers of Relic Nature I: The first estimate of the expansion rate of the Universe using compact relic galaxies

Authors: Krzysztof Lisiecki, Nicola Principi Cavaterra, Agnieszka Pollo, Chiara Spiniello, Laura Hunt, Charlie Rosen, Marek Biesiada, Darko Donevski, Patryk Matera, Giuliano Lorenzon, Katarzyna Małek, John Mills

Abstract: Measuring the expansion rate of the Universe is a central challenge in cosmology. Independent and robust methods are essential to validate existing measurements and assess potential systematic effects. We employ the cosmic chronometer (CC) approach, which uses the differential age evolution of quiescent galaxies to measure the Hubble parameter H(z) without assuming an underlying cosmological model… ▽ More Measuring the expansion rate of the Universe is a central challenge in cosmology. Independent and robust methods are essential to validate existing measurements and assess potential systematic effects. We employ the cosmic chronometer (CC) approach, which uses the differential age evolution of quiescent galaxies to measure the Hubble parameter H(z) without assuming an underlying cosmological model. In contrast to previous CC studies, we restrict our analysis to relics -- ultra compact massive galaxies (UCMGs) hosting the oldest stellar populations -- thereby minimising uncertainties related to star formation history and merger history. We select a sample of 189 relic galaxies in the redshift range 0.07< z <0.22 from the E-INSPIRE UCMGs catalogue. Using the D_n4000 spectral index of relic galaxies and its redshift evolution, combined with MILES stellar population synthesis models, we derive the differential age relation required to infer H(z). We account not only for metallicity effects but also for the impact of alpha-element enhancement, which has not been explicitly propagated into the systematic uncertainty budget of the D_n4000 cosmic chronometer method. We obtain an independent measurement of H(z=0.15) = 85\pm53 km/s/Mpc. The total uncertainty is dominated by statistical limitations. The systematic component is 13% (8.7% when alpha-enrichment is not propagated), among the tightest estimates in current CC studies. We find that alpha-enrichment plays a major role in the systematic error budget, particularly in the high metallicity regime, and must be properly accounted for in future analyses. We demonstrate the proof of concept that relic galaxies provide a promising pathway to reduce systematic uncertainties in the CC method. The statistical uncertainties, which dominate the error budget, can be significantly reduced by the increase of data volume expected during the next years. △ Less

Submitted 12 August, 2026; v1 submitted 10 August, 2026; originally announced August 2026.

The Fornax Cluster VLT Spectroscopic Survey - V. Mass modelling of the BCG NGC 1399 out to 150 kpc

Authors: Avinash Chaturvedi, Nicola R. Napolitano, Michael Hilker, Katja Fahrion, Sabine Thater, Glenn van de Ven, Michele Cantiello, Chiara Spiniello, Maurizio Paolillo, Tadeja Veršič

Abstract: NGC 1399, the bright central galaxy of the Fornax cluster, hosts an extensive population of globular clusters (GCs) extending beyond 200 kpc into its outer halo, about 6.5 effective radii (Re). We conducted dynamical mass modelling of NGC 1399 out to 5 Re (~150 kpc), using a comprehensive radial velocity catalogue of GCs, combining data from the Fornax cluster VLT spectroscopic survey (FVSS) with… ▽ More NGC 1399, the bright central galaxy of the Fornax cluster, hosts an extensive population of globular clusters (GCs) extending beyond 200 kpc into its outer halo, about 6.5 effective radii (Re). We conducted dynamical mass modelling of NGC 1399 out to 5 Re (~150 kpc), using a comprehensive radial velocity catalogue of GCs, combining data from the Fornax cluster VLT spectroscopic survey (FVSS) with prior measurements from the literature. Applying spherical Jeans equations, we performed dispersion-kurtosis modelling of NGC 1399's GC kinematics to derive its mass profile and GC orbital anisotropy. We also investigated the impact of including intra-cluster GCs in the mass modelling, selected based on spatial segregation and a velocity $σ$-clipping method. Our findings indicate that both cusp-like (NFW) and core-like (Burkert) halos can reproduce the observed kinematics of GCs. Including the intra-cluster GCs in the mass modelling yields broadly consistent mass profiles for both halo types, with the full GC sample giving a virial mass of log $\log M_{\rm vir} = 13.81 \pm 0.09~M_{\odot}$ for the NFW halo, slightly higher than the value inferred for the Burkert halo. Regardless of the dark matter halo profile adopted, we observe that the intra-cluster GCs exhibit radial anisotropy in the outskirts, especially among the blue, metal-poor GCs. These results suggest that GCs in NGC 1399's outer halo are influenced by an additional halo component associated with the galaxy cluster potential. The radial anisotropy observed in these outer-halo GCs provides strong dynamical evidence supporting their accretion from external sources, consistent with prior photometric and spectroscopic studies of GCs. This study highlights the importance of including intra-cluster GCs in dynamical mass modelling to fully account for the contribution of dark matter to the cluster gravitational potential. △ Less

Submitted 3 August, 2026; originally announced August 2026.

Comments: Accepted for publication in A&A. 23 pages, 20 figures, including a 7-page appendix with 8 figures

Looking into the faintEst WIth MUSE (LEWIS): Exploring the nature of ultra-diffuse galaxies in the Hydra-I cluster. VI. A star-forming UDG in Hydra I: a rare UDG or a transition phase?

Authors: Luca Rossi, Chiara Buttitta, Goran Doll, Enrichetta Iodice, Marco Gullieuszik, Marc Sarzi, Marco Mirabile, Johanna Hartke, Magda Arnaboldi, Rosa Calvi, Michele Cantiello, Enrico Maria Corsini, Giuseppe D'Ago, Jesús Falcón-Barroso, Francesca Fonzo, Duncan A. Forbes, Michael Hilker, Antonio La Marca, Alessandro Loni, Steffen Mieske, Maurizio Paolillo, Marina Rejkuba, Marilena Spavone, Chiara Spiniello

Abstract: This paper presents a detailed analysis of a gas-rich star-forming ultra-diffuse galaxy (UDG) as part of the ESO Large Programme 'Looking into the faintEst WIth MUSE (LEWIS)'. Among the UDGs in the LEWIS sample, UDG 6 is the only galaxy that hosts a significant amount of ionised gas with evidence of emission lines, suggesting recent star-forming activity. The main goal of this work is to constrain… ▽ More This paper presents a detailed analysis of a gas-rich star-forming ultra-diffuse galaxy (UDG) as part of the ESO Large Programme 'Looking into the faintEst WIth MUSE (LEWIS)'. Among the UDGs in the LEWIS sample, UDG 6 is the only galaxy that hosts a significant amount of ionised gas with evidence of emission lines, suggesting recent star-forming activity. The main goal of this work is to constrain the formation history of this UDG by comparing its properties with the main formation scenarios proposed for this extreme class of galaxies. We adopted integral field spectroscopy from MUSE to derive the morphology and the structural properties of the stellar and gas components of UDG 6. We applied spectral fitting and Voronoi tessellation algorithms to the MUSE data-cube to derive the kinematics and properties of the gas and stellar component. Moreover, we derived the GCs populations' properties by applying a multi-band spectrophotometric analysis. We confirmed that UDG 6 is a member of Hydra I cluster. It is characterised by a regular and elongated shape and contains a significant dust content, a metal-poor ionised gas fraction and an underlying old-to-intermediate stellar component. Evidence of local and clumpy star-forming activity has been revealed through the analysis of emission line, and an arc-like tidal feature was discovered from unsharp masking analysis. UDG 6 might originate from a 'puffed-up dwarf' whose stellar content has been stretched out to larger radii, passively evolving into a more diffuse galaxy. Being located in a dynamically active region of the cluster, characterised by tidal features and stripping phenomena, we suggest that the environmental processes have played a role in shaping the properties of UDG 6. A tidal interaction with a nearby galaxy might have triggered recent star-formation activity, without dramatically altering the coherent gas rotation in UDG 6. △ Less

Submitted 26 May, 2026; originally announced May 2026.

Comments: 13 pages, 10 figures

Euclid Quick Data Release (Q1). AstroVink: A vision transformer approach to find strong gravitational lens systems

Authors: Euclid Collaboration, S. H. Vincken, K. Rojas, M. Melchior, N. E. P. Lines, T. E. Collett, A. Verma, P. Holloway, G. Despali, S. Schuldt, R. B. Metcalf, R. Gavazzi, F. Courbin, J. A. Acevedo Barroso, B. Clément, T. Li, D. Sluse, J. Wilde, A. Melo, A. Sonnenfeld, C. Tortora, T. T. Thai, M. Millon, C. Spiniello, A. Manjón-García , et al. (280 additional authors not shown)

Abstract: We present AstroVink, a vision transformer classifier designed for automated identification of strong lens candidates in Euclid imaging. We build upon the DINOv2 encoder, fine tuned to distinguish between lens and non-lens galaxies. Our base model, trained on simulated strong lens systems and labelled non lenses, recovers 88 of the 110 lens candidates within the top 500 ranked candidates, correspo… ▽ More We present AstroVink, a vision transformer classifier designed for automated identification of strong lens candidates in Euclid imaging. We build upon the DINOv2 encoder, fine tuned to distinguish between lens and non-lens galaxies. Our base model, trained on simulated strong lens systems and labelled non lenses, recovers 88 of the 110 lens candidates within the top 500 ranked candidates, corresponding to an inspection efficiency of one lens per 5.7 inspected objects in our test set. After the Q1 data release, which yielded about 500 lens candidates, we retrained the model using high confidence lens candidates and new negatives, initially flagged as potential lenses by other classifiers but rejected during visual inspection. The retrained network further improves performance, achieving recovery of all 110 systems within the same ranking and reducing the inspection effort to one lens per 4.5 inspected objects, demonstrating that incorporating real examples significantly enhances model generalisation. An analysis of training subsets revealed that the inclusion of realistic negative examples played a key role in this improvement. Finally, we applied the retrained model to the Q1 original selection of 1.08M targets, followed by a new round of Space Warps citizen science inspection and expert vetting, where we identified a total of eight Grade A and 26 Grade B new lens candidates. These results demonstrate that transformer based architectures can recover strong lens candidates with high efficiency in real Euclid data, while substantially reducing the number of candidates requiring visual inspection. △ Less

Submitted 23 April, 2026; originally announced April 2026.

Comments: 21 pages, 6 figures, 1 table,submitted to A&A journal, dataset available at https://zenodo.org/records/17425610, software available at https://github.com/SaamieVincken/AstroVink

An automated method for planetary nebula detection with SIGNALS: first applications to NGC 4214 and NGC 4449

Authors: Nancy Yang, Johanna Hartke, Martin Bureau, Chiara Spiniello, Louis-Simon Guité, Guy Flint, Magda Arnaboldi, Ana Inés Ennis, R. Pierre Martin, Thomas Martin, Carmelle Robert, Laurie Rousseau-Nepton, Lucas M. Valenzuela, Sébastien Vicens-Mouret

Abstract: Utilising the optical imaging Fourier transform spectrograph SITELLE, the Star-formation, Ionized Gas and Nebular Abundances Legacy Survey (SIGNALS) is designed to study the connection between star-forming regions and their environments. Targeting $31$ local star-forming galaxies, its data products also lend themselves to planetary nebula (PN) surveys. We present here a new pipeline to find PNe us… ▽ More Utilising the optical imaging Fourier transform spectrograph SITELLE, the Star-formation, Ionized Gas and Nebular Abundances Legacy Survey (SIGNALS) is designed to study the connection between star-forming regions and their environments. Targeting $31$ local star-forming galaxies, its data products also lend themselves to planetary nebula (PN) surveys. We present here a new pipeline to find PNe using automated emission-line diagnostics and morphology tests, that is able to distinguish PNe from contaminants with an accuracy similar to that of past visual methods. We also perform thorough completeness tests using mock PNe inserted into the data cubes with full spectra. We apply these tools to a pilot sample of two dwarf irregular galaxies from the SIGNALS survey, NGC 4214 and NGC 4449, with other galaxies to follow. For these two galaxies, we identify $25$ PNe (including $6$ new discoveries) and $23$ PNe (including $13$ new discoveries), respectively, and calculate PN luminosity function distances of $3.09^{+0.25}_{-0.46}$ and $3.91^{+0.33}_{-0.52}$ Mpc, respectively, the latter consistent with previous estimates. We also calculate the bolometric PN specific frequency of our galaxies ($α_\mathrm{bol}$), as well as a newly defined $V$-band PN specific frequency ($α_\mathrm{V}$) based solely on the galaxies' total luminosities in that band. △ Less

Submitted 10 April, 2026; originally announced April 2026.

Comments: 21 pages, 19 figures, Accepted for publication in MNRAS

Euclid Quick Data Release (Q1). The Strong Lensing Discovery Engine F -- Bright and low-redshift strong lenses

Authors: Euclid Collaboration, L. R. Ecker, M. Fabricius, S. Seitz, R. Saglia, N. E. P. Lines, P. Holloway, T. Li, A. Verma, F. Balzer, Q. Jin, A. Manjón-García, S. H. Vincken, J. Wilde, J. A. Acevedo Barroso, J. W. Nightingale, K. Rojas, S. Schuldt, M. Walmsley, T. E. Collett, G. Despali, A. Sonnenfeld, C. Tortora, R. B. Metcalf, R. Bender , et al. (324 additional authors not shown)

Abstract: We present 72 additional galaxy-galaxy strong lenses that complement the sample discovered in the Euclid Quick Release 1 data (63.1 deg^2) of the Strong Lens Discovery Engine (SLDE) papers A-E. It is shown that previous pre-selection of potential lenses, which excluded objects from the Gaia catalogue, led to missing several bright and low-redshift strong lenses, adding more than 10% new strong len… ▽ More We present 72 additional galaxy-galaxy strong lenses that complement the sample discovered in the Euclid Quick Release 1 data (63.1 deg^2) of the Strong Lens Discovery Engine (SLDE) papers A-E. It is shown that previous pre-selection of potential lenses, which excluded objects from the Gaia catalogue, led to missing several bright and low-redshift strong lenses, adding more than 10% new strong lens candidates compared to the previous search. In total, the catalogue includes 38 "grade A" (confident) and 34 "grade B" (probable) candidates. These lenses are identified through a combination of two independent searches for bright nearby objects: one based on machine-learning models followed by expert visual inspection, and the other based solely on expert visual inspection, targeting objects not included in the initial machine-learning selection (a limitation identified only after extensive visual inspection). With these additional strong lens candidates, we augment the expected number of high-confidence candidates in the Euclid Wide Survey from previous forecasts to 120000. Detailed semi-automated lens modelling confirms at least 41 systems out of 72, a fraction consistent with that found in SLDE A (315 out of 488). These include: multiple edge-on disc lenses; sources with arcs near the lens centre; "red sources"; and an edge-on disk galaxy lensing a galaxy merger, producing two sets of lensed features, an Einstein ring and a doubly imaged component. The median redshift of these systems is $Δ$ z ~ 0.3 lower than that of the SLDE A sample. △ Less

Submitted 30 March, 2026; originally announced March 2026.

Beyond compactness: a structural-dynamical-evolutionary manifold for the stellar-to-dynamical mass ratio in ultra-compact massive galaxies

Authors: Chiara Spiniello

Abstract: Ultra-compact massive galaxies (UCMGs) exhibit elevated stellar-to-dynamical mass ratios when dynamical masses are estimated using standard virial prescriptions. This discrepancy has been interpreted as non-homology driven by their compactness. This study investigates how the stellar-to-dynamical mass ratio depends on compactness (C), velocity dispersion ($σ_*$), stellar population properties (age… ▽ More Ultra-compact massive galaxies (UCMGs) exhibit elevated stellar-to-dynamical mass ratios when dynamical masses are estimated using standard virial prescriptions. This discrepancy has been interpreted as non-homology driven by their compactness. This study investigates how the stellar-to-dynamical mass ratio depends on compactness (C), velocity dispersion ($σ_*$), stellar population properties (age, metallicity, and [Mg/Fe]), and star formation histories (SFHs). The analysis is based on a homogeneous sample of 482 UCMGs from the INSPIRE and E-INSPIRE surveys, extending to smaller sizes than previously analysed samples. I first derive the compactness-mass relation assuming a constant virial coefficient (K=5). I then correct stellar masses for IMF variations and recompute stellar-to-dynamical mass ratios using an empirical prescription where the virial coefficient varies with radius and stellar mass. Finally, I test modulation by stellar kinematics and population properties, including the degree of relicness (DoR), quantifiying the extremeness of the SFH. A statistically significant anti-correlation between compactness and the IMF-corrected stellar-to-dynamical mass ratio is recovered under a constant virial coefficient, but the relation flattens when a structure-dependent K is adopted. The data define a structural-dynamical manifold in the logC-log$σ_*$ space. Velocity dispersion sets the dominant axis of variation, and the corresponding plane accounts for ~62% of the variance in stellar-to-dynamical mass ratio. The stellar-to-dynamical mass ratio in UCMGs is governed primarily by the depth of the gravitational potential traced by $σ_*$, rather than C alone. At fixed size, systems with higher velocity dispersion show lower stellar-to-dynamical mass ratios. Non-homology therefore reflects coupled dynamical and evolutionary processes rather than purely geometric compactness. △ Less

Submitted 20 March, 2026; originally announced March 2026.

Comments: 13 pages, including Appendix, 9 figures, accepted for publication by A&A

Journal ref: A&A 709, A33 (2026)

Extragalactic Planetary Nebulae (xPNe). Chemical evolution and assembly histories of nearby galaxies using Oxygen and Argon abundances. From the local universe to cosmic dawn

Authors: Magda Arnaboldi, Ortwin Gerhard, Martin Roth, Souradeep Bhattacharya, Johanna Hartke, Chiara Spiniello, Azlizan Soemitro, Claudia Pulsoni, Lucas Valenzuela

Abstract: How galaxies formed and evolved in the expanding Universe is the main science goal of Near-Field Cosmology research. Studies of the properties of galaxies' resolved stars open a widow on their ancient galactic components, probing star formation during epochs more than 10 billion years ago. Extragalactic Planetary Nebulae (xPNe) can help decipher the signatures of mergers and interactions persistin… ▽ More How galaxies formed and evolved in the expanding Universe is the main science goal of Near-Field Cosmology research. Studies of the properties of galaxies' resolved stars open a widow on their ancient galactic components, probing star formation during epochs more than 10 billion years ago. Extragalactic Planetary Nebulae (xPNe) can help decipher the signatures of mergers and interactions persisting over many dynamical times by tracing elemental abundances coupled with their kinematics and spatial distributions. With new facilities, reaching higher angular resolution, area coverage and sensitivity, one can use xPNe to map Oxygen and Argon element abundances, in addition to their kinematics, to extend the Galactic Archeology investigation to the oldest stellar aggregates in our Local Universe. △ Less

Submitted 23 January, 2026; originally announced January 2026.

Comments: 3 pages, 2 figures, submitted to the ESO Expanding Horizons call in December 2025

Extragalactic Planetary Nebulae (xPNe). Determining Distances out to 100 Mpc and the Renaissance of the PN Luminosity Function Method

Authors: Magda Arnaboldi, Ortwin Gerhard, Martin Roth, Peter M. Weilbacher, Souradeep Bhattacharya, Johanna Hartke, Chiara Spiniello, Azlizan Soemitro, Claudia Pulsoni, Lucas Valenzuela, George Jacoby, Robin Ciardullo

Abstract: The discrepancy of the Hubble parameter H0 as measured from the cosmic microwave background versus that found from traditional distance ladder measurements has produced considerable discussion about the need for another force in cosmology. However the significance of the discrepancy depends on understanding the systematic associated with crowding, metallicity effects, and extinction of the stellar… ▽ More The discrepancy of the Hubble parameter H0 as measured from the cosmic microwave background versus that found from traditional distance ladder measurements has produced considerable discussion about the need for another force in cosmology. However the significance of the discrepancy depends on understanding the systematic associated with crowding, metallicity effects, and extinction of the stellar tracers. Thus additional precision distance indicators in the local universe are desperately needed for investigating the H0 tension. The analysis of MUSE archival data makes the case that the Planetary Nebula Luminosity Function (PNLF) has become such an indicator, as the method can reach distances comparable to HST distances of Cepheid at a fraction of a cost, in terms of telescope time and ground-based. With new wide-field spectroscopic facilities it becomes possible to measure distances to early-type galaxies (ETGs) using the PNLF out to 100 Mpc distance, achieving a precise estimate for the H0 value which is independent of the Type Ia supernova calibration, with only single-epoch measurements. △ Less

Submitted 23 January, 2026; originally announced January 2026.

Comments: 2 pages, 1 figure, submitted to the ESO Expanding Horizons call in December 2025

Extragalactic planetary nebulae -- tracers of kinematics and stellar populations out to 100 Mpc

Authors: Johanna Hartke, Magda Arnaboldi, Claudia Pulsoni, Souradeep Bhattacharya, Martin Bureau, Enrico Congiu, Guy Flint, Ortwin Gerhard, Martin Roth, Azlizan Soemitro, Chiara Spiniello, Lucas Valenzuela, Peter Weilbacher, Nancy Yang

Abstract: Extragalactic planetary nebulae (xPNe) in galaxies beyond the Local Universe serve as discrete tracers for studying the element abundances and kinematics of galaxies covering a wide range of morphologies and masses at a variety of angular distances, from the centre well out into their haloes. They are direct stellar probes to identify the galaxy progenitors of haloes and the intracluster light. Ev… ▽ More Extragalactic planetary nebulae (xPNe) in galaxies beyond the Local Universe serve as discrete tracers for studying the element abundances and kinematics of galaxies covering a wide range of morphologies and masses at a variety of angular distances, from the centre well out into their haloes. They are direct stellar probes to identify the galaxy progenitors of haloes and the intracluster light. Even with new facilities, reaching higher angular resolution and sensitivity, xPNe are the only stellar tracers that can be directly and singularly detected and characterised out to 100 Mpc distance, making them crucial for tracing halo and intracluster light assembly. New wide-field spectroscopic instruments at 10+meter-class telescopes will allow the unprecedented characterisation of xPN populations from galaxy centres to their diffuse outskirts. Panoramic integral-field spectroscopy will enable the simultaneous study of xPN and stellar population properties, establishing their use as age- and metallicity-tracers while also improving post-AGB stellar evolution models. △ Less

Submitted 16 January, 2026; originally announced January 2026.

Comments: 4 pages, 1 figure, submitted to the ESO Expanding Horizons call in December 2025

Why the Northern Hemisphere Needs a 30-40m Telescope and the Science at Stake: Shaping Galaxies and Their Stars with Stellar Population Gradients, IMF Variations and Environmental Drivers in Cluster Early-Type Galaxies

Authors: A. Vazdekis, P. Sánchez-Blázquez, A. Ferré-Mateu, I. Martín-Navarro, M. A. Beasley, J. A. L. Aguerri, A. Camps-Fariña, A. de Lorenzo-Cáceres, E. Eftekhari, J. Falcón-Barroso, I. Ferreras, F. La Barbera, R. García-Benito, R. M. González Delgado, M. Longhetti, C. Maraston, I. Pérez, F. Pinna, V. Quilis, R. F. Peletier, S. F. Sánchez-Sánchez, A. Sansom, L. Scholz-Díaz, C. Spiniello, D. Thomas , et al. (1 additional authors not shown)

Abstract: This white paper highlights how stellar population gradients, chemical abundance patterns, stellar initial mass function (IMF) variations, and structural signatures in early-type galaxies (ETGs), measured at faint and large galactocentric radii, out to $\sim4R_e$, provide powerful diagnostics of their formation and evolutionary histories. These observables encode the combined effects of early diss… ▽ More This white paper highlights how stellar population gradients, chemical abundance patterns, stellar initial mass function (IMF) variations, and structural signatures in early-type galaxies (ETGs), measured at faint and large galactocentric radii, out to $\sim4R_e$, provide powerful diagnostics of their formation and evolutionary histories. These observables encode the combined effects of early dissipative star formation, subsequent accretion and mergers, and internal feedback processes. Achieving such measurements requires high-signal-to-noise, spatially resolved U-band--optical--near-IR spectroscopy at large radii, with enough spatial resolution to study the variation of these properties on $\sim$kpc scales. These capabilities can only be delivered by a 30\,m-class telescope. Disentangling these internal processes from environmental influences further demands observations of galaxies across clusters spanning a wide range of evolutionary stages and local environments. The nearby Virgo, Perseus, and Coma clusters, without any comparable nearby counterparts in the Southern Hemisphere, offer ideal laboratories for this work. Such observations will place stringent constraints on the formation mechanism of ETGs, connecting local cluster ETGs to their high-redshift progenitors. This white paper outlines several key science cases enabled by such a facility: (1) mapping stellar population gradients across environments; (2) tracing IMF variations as a function of evolutionary stage and environment; (3) reconstructing the three-dimensional structure of galaxies through deep integral-field spectroscopy and imaging; and (4) identifying and studying compact and relic systems as progenitors of present-day ETGs. △ Less

Submitted 16 December, 2025; originally announced December 2025.

Comments: White Paper submitted to "ESO Expanding Horizons: Transforming Astronomy in the 2040s"

Looking into the faintEst WIth MUSE (LEWIS): on the nature of ultra-diffuse galaxies in the Hydra I cluster. V. Integrated stellar population properties

Authors: Goran Doll, Chiara Buttitta, Enrichetta Iodice, Anna Ferré-Mateu, Jesus Falcòn-Barroso, Ignacio Martìn-Navarro, Maurizio Paolillo, Luca Rossi, Duncan A. Forbes, Chiara Spiniello, Johanna Hartke, Marco Gullieuszik, Magda Arnaboldi, Michele Cantiello, Enrico Maria Corsini, Giuseppe D'Ago, Michael Hilker, Antonio La Marca, Steffen Mieske, Marco Mirabile, Marina Rejkuba, Marilena Spavone

Abstract: Context: This paper presents new results from the ESO Large Programme Looking into the faintEst WIth MUSE (LEWIS). The sample consists of low-surface brightness (LSB) and ultra-diffuse galaxies (UDGs) located inside 0.4 R$_{vir}$ of the Hydra I cluster. Integral field spectroscopy is acquired for 24 galaxies with the MUSE spectrograph mounted on the Very Large Telescope (VLT). Aims: Our main objec… ▽ More Context: This paper presents new results from the ESO Large Programme Looking into the faintEst WIth MUSE (LEWIS). The sample consists of low-surface brightness (LSB) and ultra-diffuse galaxies (UDGs) located inside 0.4 R$_{vir}$ of the Hydra I cluster. Integral field spectroscopy is acquired for 24 galaxies with the MUSE spectrograph mounted on the Very Large Telescope (VLT). Aims: Our main objective is to analyse possible correlations between the environment and the integrated stellar population properties. Methods: For each galaxy, we extract the 1D stacked spectrum in an aperture of one effective radius and adopt previously published stellar kinematics to derive age, metallicity and [Mg/Fe] through a full spectral fitting technique. Results: We find that the analysed LEWIS sample has a mean metallicity of [M/H] = -0.9 dex, a mean age of 10 Gyr, comparable to results of UDGs in other clusters. According to the projected phase-space, galaxies can be classified into two groups: early infallers, with slightly higher metallicities ([M/H]$_{early} = -0.8 \pm 0.1$ dex), and late infallers, with slightly lower values ([M/H]$_{late} = -1.0 \pm 0.1$ dex). Two types of galaxies are found in the early-infall region: half of them have metallicities consistent with the dwarf mass-metallicity relation, while the other half show higher values. Moreover, they display different timescales for stellar mass assembly. Conclusions: We identified different classes of UDGs in the Hydra I cluster, which suggest different formation mechanisms taking place. Almost all of the UDGs and LSBs in the cluster are consistent with the puffed-up dwarf formation scenario, having dwarf-like metallicities and being consistent with the dwarf mass-metallicity relation. In the innermost regions of the cluster, where metal-richer UDGs lie, tidal or environmental effects might have influenced their formation and evolution. △ Less

Submitted 12 December, 2025; originally announced December 2025.

Comments: 22 Pages, Accepted for publication on A&A

Journal ref: A&A 707, A88 (2026)

Planetary nebulae as tracers of stellar population properties: a pilot study with MUSE

Authors: Ana Inés Ennis, Johanna Hartke, Fuyan Bian, Claudia Pulsoni, Chiara Spiniello, Magda Arnaboldi, Roberto de Propris

Abstract: Planetary nebulae (PNe) are the only single stars in galaxies outside the Local Group that can be used as kinematic tracers of the diffuse light in the extended halo. Analysing their luminosity-specific number density across galaxies of different morphologies has also shown hints that they may be used as tracers of the age and metallicity of stellar populations. A proper understanding of this rela… ▽ More Planetary nebulae (PNe) are the only single stars in galaxies outside the Local Group that can be used as kinematic tracers of the diffuse light in the extended halo. Analysing their luminosity-specific number density across galaxies of different morphologies has also shown hints that they may be used as tracers of the age and metallicity of stellar populations. A proper understanding of this relation has been hindered by the fact that simultaneously detecting PNe and accurately measuring stellar properties is extremely difficult using classical narrow-band imaging methods, which cannot detect PNe in the bright centres of galaxies. In this work, we use integral-field spectroscopy to overcome this challenge, analysing the inner regions of a sample of ten early-type galaxies from the Extended Planetary Nebulae Survey (ePN.S) for which archival MUSE data was available. With the Diffuse Emission-Line Filter (DELF) technique, we automate the detection of PNe, and perform spectral fitting on the diffuse light to infer kinematics and stellar population parameters. We compare the PN number density profile and its associated alpha-parameter with multiple properties of the host galaxies. We find that our sample follows the previously observationally constrained correlation with the metallicity of the host galaxy. We find a weak anti-correlation between the alpha-parameter and the FUV excess, highlighting the possible relation between the visibility lifetime of PNe on the spectral energy distribution of their host galaxies, with fewer PNe detected in association with stellar populations characterized by a UV excess. △ Less

Submitted 14 November, 2025; originally announced November 2025.

Comments: 14 pages + Appendix, 19 Figures, accepted to MNRAS

Puzzling radial gradients of K-band absorption features in the giant elliptical galaxy M87

Authors: F. La Barbera, A. Vazdekis, A. Pasquali, J. Heidt, E. Eftekhari, M. A. Beasley, A. Gargiulo, S. Bisogni, C. Spiniello, L. P. Cassarà, M. Sarzi

Abstract: We present new K-band spectroscopy for the giant elliptical galaxy M87 in the Virgo cluster, taken with the LUCI spectrograph at the Large Binocular Telescope (LBT). The new data are used to study line-strengths of K-band absorption features from different chemical species, namely Fe, Mg, Ca, Na, and CO, as a function of galactocentric distance, out to 40arcsec from the center (about half of the g… ▽ More We present new K-band spectroscopy for the giant elliptical galaxy M87 in the Virgo cluster, taken with the LUCI spectrograph at the Large Binocular Telescope (LBT). The new data are used to study line-strengths of K-band absorption features from different chemical species, namely Fe, Mg, Ca, Na, and CO, as a function of galactocentric distance, out to 40arcsec from the center (about half of the galaxy effective radius). The radial trends of spectral indices are compared to those for the bulge of M31, observed with the same instrument. For M87, most K-band indices exhibit flat radial profiles, with the exception of NaI2.21, that decreases outwards, with a negative radial gradient. Significant offsets are found between indices for M87 and those for the bulge of M31, the latter having weaker line-strengths for almost all features, but Fe and Ca, for which we find similar trends in both systems. We find that the behavior of CO features - most prominent in giant stars - is difficult to explain, consistent with previous results for the central regions of massive galaxies. In particular, the CO indices are stronger in M87 than M31, and do not exhibit significant radial gradients in M87, despite its IMF being bottom heavier than M31 especially in its central region. Predictions of state-of-the-art stellar population models, based on results from the optical spectral range, are able to match only the Na and Ca indices of M87, while a significant mismatch is found for all other indices. This shows that state-of-the-art stellar population models should be improved significantly in order to provide reliable constraints on the stellar population content of galaxies in the NIR spectral range. △ Less

Submitted 6 June, 2025; originally announced June 2025.

Comments: 12 pages, 5 figures; accepted for publication in A&A

Journal ref: A&A 700, A64 (2025)

TDCOSMO 2025: Cosmological constraints from strong lensing time delays

Authors: TDCOSMO Collaboration, Simon Birrer, Elizabeth J. Buckley-Geer, Michele Cappellari, Frédéric Courbin, Frédéric Dux, Christopher D. Fassnacht, Joshua A. Frieman, Aymeric Galan, Daniel Gilman, Xiang-Yu Huang, Shawn Knabel, Danial Langeroodi, Huan Lin, Martin Millon, Takahiro Morishita, Veronica Motta, Pritom Mozumdar, Eric Paic, Anowar J. Shajib, William Sheu, Dominique Sluse, Alessandro Sonnenfeld, Chiara Spiniello, Massimo Stiavelli , et al. (8 additional authors not shown)

Abstract: We present cosmological constraints from 8 strongly lensed quasars (hereafter, the TDCOSMO-2025 sample). Building on previous work, our analysis incorporated new deflector stellar velocity dispersions measured from spectra obtained with the James Webb Space Telescope (JWST), the Keck Telescopes, and the Very Large Telescope (VLT), utilizing improved methods. We used integrated JWST stellar kinemat… ▽ More We present cosmological constraints from 8 strongly lensed quasars (hereafter, the TDCOSMO-2025 sample). Building on previous work, our analysis incorporated new deflector stellar velocity dispersions measured from spectra obtained with the James Webb Space Telescope (JWST), the Keck Telescopes, and the Very Large Telescope (VLT), utilizing improved methods. We used integrated JWST stellar kinematics for 5 lenses, VLT-MUSE for 2, and resolved kinematics from Keck and JWST for RXJ1131-1231. We also considered two samples of non-time-delay lenses: 11 from the Sloan Lens ACS (SLACS) sample with Keck-KCWI resolved kinematics; and 4 from the Strong Lenses in the Legacy Survey (SL2S) sample. We improved our analysis of line-of-sight effects, the surface brightness profile of the lens galaxies, and orbital anisotropy, and corrected for projection effects in the dynamics. Our uncertainties are maximally conservative by accounting for the mass-sheet degeneracy in the deflectors' mass density profiles. The analysis was blinded to prevent experimenter bias. Our primary result is based on the TDCOSMO-2025 sample, in combination with $Ω_{\rm m}$ constraints from the Pantheon+ Type Ia supernovae (SN) dataset. In the flat $Λ$ cold dark matter (CDM), we find $H_0=71.6^{+3.9}_{-3.3}$ km s$^{-1}$ Mpc$^{-1}$. The SLACS and SL2S samples are in excellent agreement with the TDCOSMO-2025 sample, improving the precision on $H_0$ in flat $Λ$CDM to 4.6%. Using the Dark Energy Survey SN Year-5 dataset (DES-SN5YR) or DESI-DR2 baryonic acoustic oscillations (BAO) likelihoods instead of Pantheon+ yields very similar results. We also present constraints in the open $Λ$CDM, $w$CDM, $w_0w_a$CDM, and $w_φ$CDM cosmologies. The TDCOSMO $H_0$ inference is robust and consistent across all presented cosmological models, and our cosmological constraints in them agree with those from the BAO and SN. △ Less

Submitted 20 December, 2025; v1 submitted 3 June, 2025; originally announced June 2025.

Comments: 35 pages, 17 figures, 8 tables (this version: published version in A&A). The CosmoVerse Seminar on this paper given on June 12, 2025 can be watched at https://www.youtube.com/watch?v=sr0Ft6O4VBg

Journal ref: A&A 704, A63 (2025)

INSPIRE: INvestigating Stellar Populations In RElics. IX. KiDS J0842+0059: the first fully confirmed relic beyond the local Universe

Authors: C. Tortora, G. Tozzi, G. Agapito, F. La Barbera, C. Spiniello, R. Li, G. Carlà, G. D'Ago, E. Ghose, F. Mannucci, N. R. Napolitano, E. Pinna, M. Arnaboldi, D. Bevacqua, A. Ferré-Mateu, A. Gallazzi, J. Hartke, L. K. Hunt, M. Maksymowicz-Maciata, C. Pulsoni, P. Saracco, D. Scognamiglio, M. Spavone

Abstract: Relics are massive, compact and quiescent galaxies that assembled the majority of their stars in the early Universe and lived untouched until today, completely missing any subsequent size-growth caused by mergers and interactions. They provide the unique opportunity to put constraints on the first phase of mass assembly in the Universe with the ease of being nearby. While only a few relics have be… ▽ More Relics are massive, compact and quiescent galaxies that assembled the majority of their stars in the early Universe and lived untouched until today, completely missing any subsequent size-growth caused by mergers and interactions. They provide the unique opportunity to put constraints on the first phase of mass assembly in the Universe with the ease of being nearby. While only a few relics have been found in the local Universe, the {\tt INSPIRE} project has confirmed 38 relics at higher redshifts ($z \sim 0.2-0.4$), fully characterising their integrated kinematics and stellar populations. However, given the very small sizes of these objects and the limitations imposed by the atmosphere, structural parameters inferred from ground-based optical imaging are possibly affected by systematic effects that are difficult to quantify. In this paper, we present the first high-resolution image obtained with Adaptive Optics Ks-band observations on SOUL-LUCI@LBT of one of the most extreme {\tt INSPIRE} relics, KiDS~J0842+0059 at $z \sim 0.3$. We confirm the disky morphology of this galaxy (axis ratio of $0.24$) and its compact nature (circularized effective radius of $\sim 1$ kpc) by modelling its 2D surface brightness profile with a PSF-convolved Sérsic model. We demonstrate that the surface mass density profile of KiDS~J0842+0059 closely resembles that of the most extreme local relic, NGC~1277, as well as of high-redshift red nuggets. We unambiguously conclude that this object is a remnant of a high-redshift compact and massive galaxy, which assembled all of its mass at $z>2$, and completely missed the merger phase of the galaxy evolution. △ Less

Submitted 19 May, 2025; originally announced May 2025.

Comments: Accepted for publication in MNRAS, 11 pages, 5 figures

Journal ref: Monthly Notices of the Royal Astronomical Society, Volume 540, Issue 3, July 2025, Pages 2555-2565

INSPIRE: INvestigating Stellar Population In RElics VIII. Emission lines and UV colours in ultra-compact massive galaxies

Authors: Chiara Spiniello, Mario Radovich, Anna Ferré-Mateu, Roberto De Propris, Magda Arnaboldi, Francesco La Barbera, Johanna Hartke, Giuseppe D'Ago, Crescenzo Tortora, Davide Bevacqua, Michalina Maksymowicz-Maciata, John Mills, Nicola Rosario Napolitano, Claudia Pulsoni, Paolo Saracco, Diana Scognamiglio

Abstract: We report the discovery of emission lines in the optical spectra of ultra-compact massive galaxies (UCMGs) from INSPIRE, including relics, which are the oldest galaxies in the Universe. Emission-lines diagnostic diagrams suggest that all these UCMGs, independently of their star formation histories, are `retired galaxies'. They are inconsistent with being star-forming but lie in the same region of… ▽ More We report the discovery of emission lines in the optical spectra of ultra-compact massive galaxies (UCMGs) from INSPIRE, including relics, which are the oldest galaxies in the Universe. Emission-lines diagnostic diagrams suggest that all these UCMGs, independently of their star formation histories, are `retired galaxies'. They are inconsistent with being star-forming but lie in the same region of shock-driven emissions or photoionisation models, incorporating the contribution from post-asymptotic giant branch (pAGB) stars. Furthermore, all but one INSPIRE objects have a high [OII]/Hα ratio, resembling what has been reported for normal-size red and dead galaxies. The remaining object (J1142+0012) is the only one to show clear evidence for strong active galactic nucleus activity from its spectrum. We also provide near-UV (far-UV) fluxes for 20 (5) INSPIRE objects that match in GALEX. Their NUV-r colours are consistent with those of galaxies lying in the UV green valley, but also with the presence of recently (<0.5 Gyr) formed stars at the sub-percent fraction level. This central recent star formation could have been ignited by gas that was originally ejected during the pAGB phases and then re-compressed and brought to the core by the ram-pressure stripping of Planetary Nebula envelopes. Once in the centre, it can be shocked and re-emit spectral lines. △ Less

Submitted 26 March, 2025; originally announced March 2025.

Comments: 9 pages, 4 figure, one table. Accepted for publication on MNRAS

Euclid Quick Data Release (Q1). The Strong Lensing Discovery Engine E -- Ensemble classification of strong gravitational lenses: lessons for Data Release 1

Authors: Euclid Collaboration, P. Holloway, A. Verma, M. Walmsley, P. J. Marshall, A. More, T. E. Collett, N. E. P. Lines, L. Leuzzi, A. Manjón-García, S. H. Vincken, J. Wilde, R. Pearce-Casey, I. T. Andika, J. A. Acevedo Barroso, T. Li, A. Melo, R. B. Metcalf, K. Rojas, B. Clément, H. Degaudenzi, F. Courbin, G. Despali, R. Gavazzi, S. Schuldt , et al. (321 additional authors not shown)

Abstract: The Euclid Wide Survey (EWS) is expected to identify of order $100\,000$ galaxy-galaxy strong lenses across $14\,000$deg$^2$. The Euclid Quick Data Release (Q1) of $63.1$deg$^2$ Euclid images provides an excellent opportunity to test our lens-finding ability, and to verify the anticipated lens frequency in the EWS. Following the Q1 data release, eight machine learning networks from five teams were… ▽ More The Euclid Wide Survey (EWS) is expected to identify of order $100\,000$ galaxy-galaxy strong lenses across $14\,000$deg$^2$. The Euclid Quick Data Release (Q1) of $63.1$deg$^2$ Euclid images provides an excellent opportunity to test our lens-finding ability, and to verify the anticipated lens frequency in the EWS. Following the Q1 data release, eight machine learning networks from five teams were applied to approximately one million images. This was followed by a citizen science inspection of a subset of around $100\,000$ images, of which $65\%$ received high network scores, with the remainder randomly selected. The top scoring outputs were inspected by experts to establish confident (grade A), likely (grade B), possible (grade C), and unlikely lenses. In this paper we combine the citizen science and machine learning classifiers into an ensemble, demonstrating that a combined approach can produce a purer and more complete sample than the original individual classifiers. Using the expert-graded subset as ground truth, we find that this ensemble can provide a purity of $52\pm2\%$ (grade A/B lenses) with $50\%$ completeness (for context, due to the rarity of lenses a random classifier would have a purity of $0.05\%$). We discuss future lessons for the first major Euclid data release (DR1), where the big-data challenges will become more significant and will require analysing more than $\sim300$ million galaxies, and thus time investment of both experts and citizens must be carefully managed. △ Less

Submitted 19 March, 2025; originally announced March 2025.

Comments: Paper submitted as part of the A&A Special Issue `Euclid Quick Data Release (Q1)', 15 pages, 8 figures

Euclid Quick Data Release (Q1). The Strong Lensing Discovery Engine C: Finding lenses with machine learning

Authors: Euclid Collaboration, N. E. P. Lines, T. E. Collett, M. Walmsley, K. Rojas, T. Li, L. Leuzzi, A. Manjón-García, S. H. Vincken, J. Wilde, P. Holloway, A. Verma, R. B. Metcalf, I. T. Andika, A. Melo, M. Melchior, H. Domínguez Sánchez, A. Díaz-Sánchez, J. A. Acevedo Barroso, B. Clément, C. Krawczyk, R. Pearce-Casey, S. Serjeant, F. Courbin, G. Despali , et al. (328 additional authors not shown)

Abstract: Strong gravitational lensing has the potential to provide a powerful probe of astrophysics and cosmology, but fewer than 1000 strong lenses have been confirmed so far. With a 0.16'' resolution covering a third of the sky, the Euclid telescope will revolutionise the identification of strong lenses, with 170 000 lenses forecasted to be discovered amongst the 1.5 billion galaxies it will observe. We… ▽ More Strong gravitational lensing has the potential to provide a powerful probe of astrophysics and cosmology, but fewer than 1000 strong lenses have been confirmed so far. With a 0.16'' resolution covering a third of the sky, the Euclid telescope will revolutionise the identification of strong lenses, with 170 000 lenses forecasted to be discovered amongst the 1.5 billion galaxies it will observe. We present an analysis of the performance of five machine-learning models at finding strong gravitational lenses in the quick release of Euclid data (Q1) covering 63 deg2. The models have been validated by citizen scientists and expert visual inspection. We focus on the best-performing network: a fine-tuned version of the Zoobot pretrained model originally trained to classify galaxy morphologies in heterogeneous astronomical imaging surveys. Of the one million Q1 objects that Zoobot was tasked to find strong lenses within, the top 1000 ranked objects contain 122 grade A lenses (almost-certain lenses) and 41 grade B lenses (probable lenses). A deeper search with the five networks combined with visual inspection yielded 250 (247) grade A (B) lenses, of which 224 (182) are ranked in the top 20 000 by Zoobot. When extrapolated to the full Euclid survey, the highest ranked one million images will contain 75 000 grade A or B strong gravitational lenses. △ Less

Submitted 26 June, 2025; v1 submitted 19 March, 2025; originally announced March 2025.

Comments: Paper accepted for the A&A Special Issue `Euclid Quick Data Release (Q1)', 24 pages

Euclid Quick Data Release (Q1): The Strong Lensing Discovery Engine A -- System overview and lens catalogue

Authors: Euclid Collaboration, M. Walmsley, P. Holloway, N. E. P. Lines, K. Rojas, T. E. Collett, A. Verma, T. Li, J. W. Nightingale, G. Despali, S. Schuldt, R. Gavazzi, A. Melo, R. B. Metcalf, I. T. Andika, L. Leuzzi, A. Manjón-García, R. Pearce-Casey, S. H. Vincken, J. Wilde, V. Busillo, C. Tortora, J. A. Acevedo Barroso, H. Dole, L. R. Ecker , et al. (350 additional authors not shown)

Abstract: We present a catalogue of 497 galaxy-galaxy strong lenses in the Euclid Quick Release 1 data (63 deg$^2$). In the initial 0.45\% of Euclid's surveys, we double the total number of known lens candidates with space-based imaging. Our catalogue includes 250 grade A candidates, the vast majority of which (243) were previously unpublished. Euclid's resolution reveals rare lens configurations of scienti… ▽ More We present a catalogue of 497 galaxy-galaxy strong lenses in the Euclid Quick Release 1 data (63 deg$^2$). In the initial 0.45\% of Euclid's surveys, we double the total number of known lens candidates with space-based imaging. Our catalogue includes 250 grade A candidates, the vast majority of which (243) were previously unpublished. Euclid's resolution reveals rare lens configurations of scientific value including double-source-plane lenses, edge-on lenses, complete Einstein rings, and quadruply-imaged lenses. We resolve lenses with small Einstein radii ($θ_{\rm E} < 1''$) in large numbers for the first time. These lenses are found through an initial sweep by deep learning models, followed by Space Warps citizen scientist inspection, expert vetting, and system-by-system modelling. Our search approach scales straightforwardly to Euclid Data Release 1 and, without changes, would yield approximately 7000 high-confidence (grade A or B) lens candidates by late 2026. Further extrapolating to the complete Euclid Wide Survey implies a likely yield of over 100000 high-confidence candidates, transforming strong lensing science. △ Less

Submitted 19 March, 2025; originally announced March 2025.

Comments: Data: https://doi.org/10.5281/zenodo.15003116. Paper submitted as part of the A&A Special Issue `Euclid Quick Data Release (Q1)'. 20 pages, 11 figures, plus appendices

Euclid Quick Data Release (Q1). Exploring galaxy morphology across cosmic time through Sersic fits

Authors: Euclid Collaboration, L. Quilley, I. Damjanov, V. de Lapparent, A. Paulino-Afonso, H. Domínguez Sánchez, A. Ferré-Mateu, M. Huertas-Company, M. Kümmel, D. Delley, C. Spiniello, M. Baes, L. Wang, U. Kuchner, F. Tarsitano, R. Ragusa, M. Siudek, C. Tortora, N. Aghanim, B. Altieri, A. Amara, S. Andreon, N. Auricchio, H. Aussel, C. Baccigalupi , et al. (311 additional authors not shown)

Abstract: We present the results of the single-component Sérsic profile fitting for the magnitude-limited sample of \IE$<23$ galaxies within the 63.1 deg$^2$ area of the Euclid Quick Data Release (Q1). The associated morphological catalogue includes two sets of structural parameters fitted using \texttt{SourceXtractor++}: one for VIS \IE images and one for a combination of three NISP images in \YE, \JE and… ▽ More We present the results of the single-component Sérsic profile fitting for the magnitude-limited sample of \IE$<23$ galaxies within the 63.1 deg$^2$ area of the Euclid Quick Data Release (Q1). The associated morphological catalogue includes two sets of structural parameters fitted using \texttt{SourceXtractor++}: one for VIS \IE images and one for a combination of three NISP images in \YE, \JE and \HE bands. We compare the resulting Sérsic parameters to other morphological measurements provided in the Q1 data release, and to the equivalent parameters based on higher-resolution \HST imaging. These comparisons confirm the consistency and the reliability of the fits to Q1 data. Our analysis of colour gradients shows that NISP profiles have systematically smaller effective radii ($R_{\rm e}$) and larger Sérsic indices ($n$) than in VIS. In addition, we highlight trends in NISP-to-VIS parameter ratios with both magnitude and $n_{\rm VIS}$. From the 2D bimodality of the $(u-r)$ colour-$\log(n)$ plane, we define a $(u-r)_{\rm lim}(n)$ that separates early- and late-type galaxies (ETGs and LTGs). We use the two subpopulations to examine the variations of $n$ across well-known scaling relations at $z<1$. ETGs display a steeper size--stellar mass relation than LTGs, indicating a difference in the main drivers of their mass assembly. Similarly, LTGs and ETGs occupy different parts of the stellar mass--star-formation rate plane, with ETGs at higher masses than LTGs, and further down below the Main Sequence of star-forming galaxies. This clear separation highlights the link known between the shutdown of star formation and morphological transformations in the Euclid imaging data set. In conclusion, our analysis demonstrates both the robustness of the Sérsic fits available in the Q1 morphological catalogue and the wealth of information they provide for studies of galaxy evolution with Euclid. △ Less

Submitted 1 September, 2025; v1 submitted 19 March, 2025; originally announced March 2025.

Comments: Paper accepted as part of the A&A Special Issue `Euclid Quick Data Release (Q1)', 23 pages, 16 figures

Optical+NIR analysis of a Newly Confirmed Einstein ring at z$\sim$1 from the Kilo-Degree Survey: Dark matter fraction, total and dark matter density slope and IMF

Authors: Rui Li, Nicola R. Napolitano, Giuseppe D Ago, Vyacheslav N. Shalyapin, Kai Zhu, Xiaotong Guo, Ran Li, Leon V. E. Koopmans, Chiara Spiniello, Crescenzo Tortora, Francesco La Barbera, Haicheng Feng, Liang Gao, Zhiqi Huang, Koen Kuijken, Hui Li, Linghua Xie, Mario Radovich, Alexey Sergeyev

Abstract: We report the spectroscopic confirmation of a bright blue Einstein ring in the Kilo Degree Survey (KiDS) footprint: the Einstein ``blue eye''. Spectroscopic data from X-Shooter at the Very Large Telescope (VLT) show that the lens is a typical early-type galaxy (ETG) at $z_l=0.9906$, while the background source is a Ly$α$ emitter at $z_s=2.823$. The reference lens modeling was performed on a high-r… ▽ More We report the spectroscopic confirmation of a bright blue Einstein ring in the Kilo Degree Survey (KiDS) footprint: the Einstein ``blue eye''. Spectroscopic data from X-Shooter at the Very Large Telescope (VLT) show that the lens is a typical early-type galaxy (ETG) at $z_l=0.9906$, while the background source is a Ly$α$ emitter at $z_s=2.823$. The reference lens modeling was performed on a high-resolution $Y-$band adaptive-optics image from HAWK-I at VLT. Assuming a singular isothermal ellipsoid (SIE) total mass density profile, we inferred an Einstein radius $R_{Ein}=10.47 \pm 0.06$ kpc. The average slope of the total mass density inside the Einstein radius, as determined by a joint analysis of lensing and isotropic Jeans equations is $γ_{tot}=2.14^{+0.06}_{-0.07}$, showing no systematic deviation from the slopes of lower redshift galaxies, This can be the evidence of ETGs developing through dry mergers plus moderate dissipationless accretion. Stellar population analysis with 8-band ($gri$ZYJHK$s$) photometries from KiDS and VIKING shows that the total stellar mass of the lens is $M*=(3.95\pm 0.35)\times 10^{11} M_\odot$ (Salpeter Initial Mass Function, IMF), implying a dark matter fraction inside the effective radius to be $f_{\rm DM}=0.307\pm 0.151$. We finally explored the dark matter halo slope and found a strong degeneracy with the dynamic stellar mass. Dark matter adiabatic contraction is needed to explain the posterior distribution of the slope unless IMF heavier than Salpeter is assumed. △ Less

Submitted 2 September, 2025; v1 submitted 13 March, 2025; originally announced March 2025.

Comments: 14 pages, 4 figures, 2 tables, published by APJL

TDCOSMO XIX. Measuring stellar velocity dispersion with sub-percent accuracy for cosmography

Authors: Shawn Knabel, Pritom Mozumdar, Anowar J. Shajib, Tommaso Treu, Michele Cappellari, Chiara Spiniello, Simon Birrer

Abstract: The stellar velocity dispersion ($σ$) of massive elliptical galaxies is a key ingredient in breaking the mass-sheet degeneracy and obtaining precise and accurate cosmography from gravitational time delays. The relative uncertainty on the Hubble constant H$_0$ is double the relative error on $σ$. Therefore, time-delay cosmography imposes much more demanding requirements on the precision and accurac… ▽ More The stellar velocity dispersion ($σ$) of massive elliptical galaxies is a key ingredient in breaking the mass-sheet degeneracy and obtaining precise and accurate cosmography from gravitational time delays. The relative uncertainty on the Hubble constant H$_0$ is double the relative error on $σ$. Therefore, time-delay cosmography imposes much more demanding requirements on the precision and accuracy of $σ$ than galaxy studies. While precision can be achieved with an adequate signal-to-noise ratio (S/N), the accuracy critically depends on key factors such as the elemental abundance and temperature of stellar templates, flux calibration, and wavelength ranges. We carried out a detailed study of the problem using multiple sets of galaxy spectra of massive elliptical galaxies with S/N$\sim$30--160 Å$^{-1}$, along with state-of-the-art empirical and semi-empirical stellar libraries and stellar population synthesis templates. We show that the choice of stellar library is generally the dominant source of residual systematic errors. We propose a general recipe for mitigating and accounting for residual uncertainties. We show that a sub-percent level of accuracy can be achieved on individual spectra with our data quality, which we subsequently validated with simulated mock datasets. The covariance between velocity dispersions measured for a sample of spectra can also be reduced to sub-percent levels. We recommend this recipe for all applications that require high precision and accurate stellar kinematics. Thus, we have made all the software publicly available to facilitate its implementation. This recipe will also be used in future TDCOSMO collaboration papers. △ Less

Submitted 1 January, 2026; v1 submitted 21 February, 2025; originally announced February 2025.

Comments: Final accepted version to A&A

Journal ref: A&A 703, A117 (2025)

Looking into the faintEst WIth MUSE (LEWIS): Exploring the nature of ultra-diffuse galaxies in the Hydra I cluster III. Untangling UDG 32 from the stripped filaments of NGC 3314A with multi-wavelength data

Authors: J. Hartke, E. Iodice, M. Gullieuszik, M. Mirabile, C. Buttitta, G. Doll, G. D'Ago, C. C. de la Casa, K. M. Hess, R. Kotulla, B. Poggianti, M. Arnaboldi, M. Cantiello, E. M. Corsini, J. Falcón-Barroso, D. A. Forbes, M. Hilker, S. Mieske, M. Rejkuba, M. Spavone, C. Spiniello

Abstract: UDG 32 is an ultra-diffuse galaxy (UDG) candidate in the Hydra I cluster that was discovered in the extended network of stellar filaments of the jellyfish galaxy NGC 3314A. This galaxy is affected by ram pressure stripping and it is hypothesised that UDG 32 may have formed from its stripped material. In this paper, we address whether UDG 32 can be associated with the stripped material of NGC 3314A… ▽ More UDG 32 is an ultra-diffuse galaxy (UDG) candidate in the Hydra I cluster that was discovered in the extended network of stellar filaments of the jellyfish galaxy NGC 3314A. This galaxy is affected by ram pressure stripping and it is hypothesised that UDG 32 may have formed from its stripped material. In this paper, we address whether UDG 32 can be associated with the stripped material of NGC 3314A and constrain its formation scenario in relation to its environment. We use new integral-field spectroscopic data from the MUSE large programme `LEWIS' in conjunction with deep multi-band photometry to constrain the kinematics and stellar populations of UDG 32. The new MUSE data allow us to reveal that the stripped material from NGC 3314A, traced by emission lines such as H$α$, extends much further from its parent galaxy than previously known, completely overlapping with UDG 32 in projection, and with ram pressure induced star formation. We determine the line-of-sight velocity of UDG 32 ($v_{\rm LOS} = 3080\pm120$ km/s) and confirm that UDG 32 is part of the same kinematic structure as NGC 3314A, the Hydra I cluster south-east subgroup. By fitting the UV and optical spectral energy distribution, we constrain the stellar population properties of UDG 32. We determine its mass-weighted age to be $7.7^{+2.9}_{-2.8}$ Gyr and its metallicity to be [M/H] = $0.07^{+0.19}_{-0.32}$ dex. We confirm the presence of two globular clusters (GCs) in the MUSE field of view, bound to the Hydra I cluster rather than to UDG 32, thus part of the Hydra I intracluster GC population. The metal-rich and intermediate-age nature of UDG 32 points towards its formation from pre-enriched material in the south-east group of the Hydra I cluster that was liberated from a more massive galaxy via tidal or ram-pressure stripping, but we cannot establish a direct link to the ram-pressure stripped material from NGC 3314A. △ Less

Submitted 27 January, 2025; originally announced January 2025.

Comments: 17 pages, 16 figures, accepted for publication in Astronomy and Astrophysics, abstract abridged for arxiv submission

Journal ref: A&A 695, A91 (2025)

Looking into the faintEst WIth MUSE (LEWIS): Exploring the nature of ultra-diffuse galaxies in the Hydra-I cluster II. Stellar kinematics and dynamical masses

Authors: Chiara Buttitta, Enrichetta Iodice, Goran Doll, Johanna Hartke, Michael Hilker, Duncan A. Forbes, Enrico M. Corsini, Luca Rossi, Magda Arnaboldi, Michele Cantiello, Giuseppe D'Ago, Jesus Falcon-Barroso, Marco Gullieuszik, Antonio La Marca, Steffen Mieske, Marco Mirabile, Maurizio Paolillo, Marina Rejkuba, Marilena Spavone, Chiara Spiniello, Marc Sarzi

Abstract: Context: This paper focuses on a class of galaxies characterised by an extremely low surface brightness: the ultra-diffuse galaxies (UDGs). We used new integral-field spectroscopic data from the ESO Large Programme Looking into the faintEst WIth MUSE (LEWIS) project. Aims: Our main goals are addressing the formation channels and investigating possible correlations of their observational properties… ▽ More Context: This paper focuses on a class of galaxies characterised by an extremely low surface brightness: the ultra-diffuse galaxies (UDGs). We used new integral-field spectroscopic data from the ESO Large Programme Looking into the faintEst WIth MUSE (LEWIS) project. Aims: Our main goals are addressing the formation channels and investigating possible correlations of their observational properties. In particular, we derive their stellar kinematics and dynamical properties. Methods: We extract the 1D stacked spectrum inside the effective radius to obtain an unbiased measure of $σ_{\rm eff}$. To derive the spatially-resolved stellar kinematics, we first apply the Voronoi tessellation algorithm to bin the spaxels in the datacube and then follow the same prescription adopted for the 1D case. In addition, we extract the velocity profiles along the galaxy's major and minor axes. Results: We find that 7 out of 18 UDGs in LEWIS show a mild rotation, 5 do not have evidence of any rotation, and the remaining 6 UDGs are unconstrained cases. This is the first large census of velocity profiles for UDGs. On average, UDGs in LEWIS are characterised by low values of $σ_{\rm eff}$, comparable with available values from the literature. In the Faber-Jackson relation plane, we found a group of UDGs consistent with the relation within the errorbars, whereas outliers are objects with non-negligible rotation components. UDGs and LSBs in LEWIS have larger dark matter content than dwarf galaxies with similar total luminosity. We do not find clear correlations between the derived properties and the local environment. Conclusions: Based on the stellar kinematics, two classes of UDGs are found in the Hydra I cluster: the rotating and non-rotating systems. This result, combined with other structural properties, can help to discriminate between the several formation scenarios proposed for UDGs. △ Less

Submitted 27 January, 2025; originally announced January 2025.

Comments: Accepted for publication in Astronomy and Astrophysics

Journal ref: A&A 694, A276 (2025)

E-INSPIRE -- I. Bridging the gap with the local Universe: Stellar population of a statistical sample of ultra-compact massive galaxies at $z<0.3$

Authors: John Mills, Chiara Spiniello, Alexey Sergeyev, Crescenzo Tortora, Vladyslav Khramtsov, Giuseppe D'Ago, Michalina Maksymowicz-Maciata, João P. V. Benedetti, Anna Ferré-Mateu, Michele Cappellari, Roger Davies, Johanna Hartke, Charles Rosen

Abstract: This paper presents the first effort to Extend the Investigation of Stellar Populations In RElics (E-INSPIRE). We present a catalogue of 430 spectroscopically-confirmed ultra-compact massive galaxies (UCMGs) from the Sloan Digital Sky Survey at redshifts $0.01<z<0.3$. This increases the original INSPIRE sample eightfold, bridging the gap with the local Universe. For each object, we compute integra… ▽ More This paper presents the first effort to Extend the Investigation of Stellar Populations In RElics (E-INSPIRE). We present a catalogue of 430 spectroscopically-confirmed ultra-compact massive galaxies (UCMGs) from the Sloan Digital Sky Survey at redshifts $0.01<z<0.3$. This increases the original INSPIRE sample eightfold, bridging the gap with the local Universe. For each object, we compute integrated stellar velocity dispersion, age, metallicity, and [Mg/Fe] through spectroscopic stellar population analysis. We infer star formation histories (SFHs), metallicity evolution histories (MEHs) and compute the Degree of Relicness (DoR) of each object. The UCMGs, covering a wide range of DoR from 0.05 to 0.88, can be divided into three groups, according to how extreme their SFH was. The first group consists of 81 extreme relics ($\text{DoR}\gtrsim0.6$) that have formed the totality of their stellar mass by $z\sim2$ and have super-solar metallicities at all cosmic epochs. The second group ($0.3\lesssim\text{DoR}\lesssim0.6$) contains 293 objects also characterised by peaked SFHs but with a small percentage of later-formed stars and with a variety of MEHs. The third group ($\text{DoR}\lesssim0.3$), has 56 objects that cannot be considered relics since they have extended SFHs and formed a non-negligible fraction ($>25\%$) of their stellar mass at $z<2$. We confirm that an efficient method of finding relics is to select UCMGs with large velocity dispersion values but we believe that the most efficient way is to select high velocity dispersion objects that also have super-solar metallicities and high [Mg/Fe]. △ Less

Submitted 27 January, 2025; originally announced January 2025.

Comments: 19 pages, 21 figures, submitted to MNRAS - minor revision requested by the referee

TP-AGB stars and stellar population properties of a post-starburst galaxy at $z \sim 2$ through optical and NIR spectroscopy with JWST

Authors: Davide Bevacqua, Paolo Saracco, Francesco La Barbera, Guido De Marchi, Roberto De Propris, Fabio Ditrani, Anna R. Gallazzi, Giovanna Giardino, Danilo Marchesini, Anna Pasquali, Tim D. Rawle, Chiara Spiniello, Alexandre Vazdekis, Stefano Zibetti

Abstract: We present a detailed optical and NIR spectral analysis of J-138717, a post-starburst galaxy at $z = 1.8845$ observed with JWST/NIRSpec, for which we derive a stellar mass of $3.5 \pm 0.2 \times 10^{10}$ M$_\odot$ and a stellar velocity dispersion of $198 \pm 10$ km s$^{-1}$. We estimate an age of $\sim0.9$ Gyr and a sub-solar metallicity (between $-0.4$ and $-0.2$ dex). We find generally consiste… ▽ More We present a detailed optical and NIR spectral analysis of J-138717, a post-starburst galaxy at $z = 1.8845$ observed with JWST/NIRSpec, for which we derive a stellar mass of $3.5 \pm 0.2 \times 10^{10}$ M$_\odot$ and a stellar velocity dispersion of $198 \pm 10$ km s$^{-1}$. We estimate an age of $\sim0.9$ Gyr and a sub-solar metallicity (between $-0.4$ and $-0.2$ dex). We find generally consistent results when fitting the optical and NIR wavelength ranges separately or using different model libraries. The reconstruction of the star formation history indicates that the galaxy assembled most of its mass quickly and then rapidly quenched, $\sim0.4$ Gyr prior to observation. Line diagnostics suggest that the weak emission is probably powered by residual star formation (SFR$\sim0.2$M$_\odot$ yr$^{-1}$) or a low-luminosity AGN, with no strong evidence for outflows in ionized or neutral gas. We perform a detailed study of the NIR spectral indices by comparing observations with predictions of several state-of-the-art stellar population models. This is unprecedented at such a high redshift. In particular, the analysis of several CO and CN features argues against a heavy contribution of Thermally Pulsating (TP-)AGB stars. Observations align better with models that include a minimal contribution from TP-AGB stars, but they are also consistent with a mild contribution from TP-AGB stars, assuming a younger age (consistent with the fits). The analysis of other NIR spectral indices shows that current models struggle to reproduce observations. This highlights the need for improved stellar population models in the NIR, especially at young ages and low metallicities, which is most relevant for studying high redshift galaxies in the JWST era. △ Less

Submitted 23 May, 2025; v1 submitted 13 January, 2025; originally announced January 2025.

Comments: Accepted for publication in Astronomy & Astrophysics

Journal ref: A&A 699, A203 (2025)

INSPIRE: INvestigating Stellar Population In RElics -- VII. The local environment of ultra-compact massive galaxies

Authors: Diana Scognamiglio, Chiara Spiniello, Mario Radovich, Crescenzo Tortora, Nicola R. Napolitano, Rui Li, Matteo Maturi, Michalina Maksymowicz-Maciata, Michele Cappellari, Magda Arnaboldi, Davide Bevacqua, Lodovico Coccato, Giuseppe D'Ago, Hai-Cheng Feng, Anna Ferré-Mateu, Johanna Hartke, Ignacio Martín-Navarro, Claudia Pulsoni

Abstract: Relic galaxies, the oldest ultra-compact massive galaxies (UCMGs), contain almost exclusively "pristine" stars formed during an intense star formation (SF) burst at high redshift. As such, they allow us to study in detail the early mechanism of galaxy assembly in the Universe. Using the largest catalogue of spectroscopically confirmed UCMGs for which a degree of relicness (DoR) had been estimated,… ▽ More Relic galaxies, the oldest ultra-compact massive galaxies (UCMGs), contain almost exclusively "pristine" stars formed during an intense star formation (SF) burst at high redshift. As such, they allow us to study in detail the early mechanism of galaxy assembly in the Universe. Using the largest catalogue of spectroscopically confirmed UCMGs for which a degree of relicness (DoR) had been estimated, the INSPIRE catalogue, we investigate whether or not relics prefer dense environments. The objective of this study is to determine if the DoR, which measures how extreme the SF history was, and the surrounding environment are correlated. In order to achieve this goal, we employ the AMICO galaxy cluster catalogue to compute the probability for a galaxy to be a member of a cluster, and measure the local density around each UCMG using machine learning-based photometric redshifts. We find that UCMGs can reside both in clusters and in the field, but objects with very low DoR (< 0.3, i.e., a relatively extended SF history) prefer under-dense environments. We additionally report a correlation between the DoR and the distance from the cluster centre: more extreme relics, when located in clusters, tend to occupy the more central regions of them. We finally outline potential evolution scenarios for UCMGs at different DoR to reconcile their presence in both clusters and field environments △ Less

Submitted 18 September, 2024; originally announced September 2024.

Comments: Accepted for publication on MNRAS, 11 pages, 8 figure, 1 table

A new perspective on the stellar Mass-Metallicity Relation of quiescent galaxies from the LEGA-C survey

Authors: D. Bevacqua, P. Saracco, A. Boecker, G. D'Ago, G. De Lucia, R. De Propris, F. La Barbera, A. Pasquali, C. Spiniello, C. Tortora

Abstract: We investigate the stellar Mass-Metallicity Relation (MZR) using a sample of 637 quiescent galaxies with 10.4 <= log(M*/M ) < 11.7 selected from the LEGA-C survey at 0.6 <= z <= 1. We derive mass-weighted stellar metallicities using full-spectral fitting. We find that while lower-mass galaxies are both metal -rich and -poor, there are no metal-poor galaxies at high masses, and that metallicity is… ▽ More We investigate the stellar Mass-Metallicity Relation (MZR) using a sample of 637 quiescent galaxies with 10.4 <= log(M*/M ) < 11.7 selected from the LEGA-C survey at 0.6 <= z <= 1. We derive mass-weighted stellar metallicities using full-spectral fitting. We find that while lower-mass galaxies are both metal -rich and -poor, there are no metal-poor galaxies at high masses, and that metallicity is bounded at low values by a mass-dependent lower limit. This lower limit increases with mass, empirically defining a MEtallicity-Mass Exclusion (MEME) zone. We find that the spectral index MgFe = \sqrt{Mgb \times Fe4383}, a proxy for the stellar metallicity, also shows a mass-dependent lower limit resembling the MEME relation. Crucially, MgFe is independent of stellar population models and fitting methods. By constructing the Metallicity Enrichment Histories, we find that, after the first Gyr, the Star Formation History of galaxies has a mild impact on the observed metallicity distribution. Finally, from the average formation times, we find that galaxies populate differently the metallicity-mass plane at different cosmic times, and that the MEME limit is recovered by galaxies that formed at z >= 3. Our work suggests that the stellar metallicity of quiescent galaxies is bounded by a lower limit which increases with the stellar mass. On the other hand, low-mass galaxies can have metallicities as high as galaxies ~1 dex more massive. This suggests that, at log(M*/M ) >= 10.4, rather than lower-mass galaxies being systematically less metallic, the observed MZR might be a consequence of the lack of massive, metal-poor galaxies. △ Less

Submitted 17 July, 2024; originally announced July 2024.

Comments: Accepted for publication in A&A

Journal ref: A&A 690, A150 (2024)

Retrieval of the physical parameters of galaxies from WEAVE-StePS-like data using machine learning

Authors: J. Angthopo, B. R. Granett, F. La Barbera, M. Longhetti, A. Iovino, M. Fossati, F. R. Ditrani, L. Costantin, S. Zibetti, A. Gallazzi, P. Sánchez-Blázquez, C. Tortora, C. Spiniello, B. Poggianti, A. Vazdekis, M. Balcells, S. Bardelli, C. R. Benn, M. Bianconi, M. Bolzonella, G. Busarello, L. P. Cassarà, E. M. Corsini, O. Cucciati, G. Dalton , et al. (24 additional authors not shown)

Abstract: The WHT Enhanced Area Velocity Explorer (WEAVE) is a new, massively multiplexing spectrograph. This new instrument will be exploited to obtain high S/N spectra of $\sim$25000 galaxies at intermediate redshifts for the WEAVE Stellar Population Survey (WEAVE-StePS). We test machine learning methods for retrieving the key physical parameters of galaxies from WEAVE-StePS-like spectra using both photom… ▽ More The WHT Enhanced Area Velocity Explorer (WEAVE) is a new, massively multiplexing spectrograph. This new instrument will be exploited to obtain high S/N spectra of $\sim$25000 galaxies at intermediate redshifts for the WEAVE Stellar Population Survey (WEAVE-StePS). We test machine learning methods for retrieving the key physical parameters of galaxies from WEAVE-StePS-like spectra using both photometric and spectroscopic information at various S/Ns and redshifts. We simulated $\sim$105000 galaxy spectra assuming SFH with an exponentially declining star formation rate, covering a wide range of ages, stellar metallicities, sSFRs, and dust extinctions. We then evaluated the ability of the random forest and KNN algorithms to correctly predict such parameters assuming no measurement errors. We checked how much the predictive ability deteriorates for different S/Ns and redshifts, finding that both algorithms still accurately estimate the ages and metallicities with low bias. The dispersion varies from 0.08-0.16 dex for ages and 0.11-0.25 dex for metallicity, depending on the redshift and S/N. For dust attenuation, we find a similarly low bias and dispersion. For the sSFR, we find a very good constraining power for star-forming galaxies, log sSFR$\gtrsim$ -11, where the bias is $\sim$ 0.01 dex and the dispersion is $\sim$ 0.10 dex. For more quiescent galaxies, with log sSFR$\lesssim$ -11, we find a higher bias, 0.61-0.86 dex, and a higher dispersion, $\sim$ 0.4 dex, for different S/Ns and redshifts. Generally, we find that the RF outperforms the KNN. Finally, the retrieved sSFR was used to successfully classify galaxies as part of the blue cloud, green valley, or red sequence. We demonstrate that machine learning algorithms can accurately estimate the physical parameters of simulated galaxies even at relatively low S/N=10 per angstrom spectra with available ancillary photometric information. △ Less

Submitted 17 June, 2024; originally announced June 2024.

Comments: 19 pages, 10 + 2 figures, 4 tables, accepted in A&A

INSPIRE: INvestigating Stellar Population In RElics VI -- The low-mass end slope of the stellar Initial Mass Function and chemical composition

Authors: Michalina Maksymowicz-Maciata, Chiara Spiniello, Ignacio Martín-Navarro, Anna Ferré-Mateu, Davide Bevacqua, Michele Cappellari, Giuseppe D'Ago, Crescenzo Tortora, Magda Arnaboldi, Johanna Hartke, Paolo Saracco, Diana Scognamiglio

Abstract: The INSPIRE project has built the largest sample of ultra-compact massive galaxies (UCMGs) at 0.1<z<0.4 and obtained their star formation histories (SFHs). Due to their preserved very old stellar populations, relics are the perfect systems to constrain the earliest epochs of mass assembly in the Universe and the formation of massive early-type galaxies. The goal of this work is to investigate whet… ▽ More The INSPIRE project has built the largest sample of ultra-compact massive galaxies (UCMGs) at 0.1<z<0.4 and obtained their star formation histories (SFHs). Due to their preserved very old stellar populations, relics are the perfect systems to constrain the earliest epochs of mass assembly in the Universe and the formation of massive early-type galaxies. The goal of this work is to investigate whether a correlation exists between the degree of relicness (DoR), quantifying the fraction of stellar mass formed at z>2, and the other stellar population parameters.We use the Full-Index-Fitting method to fit the INSPIRE spectra to single stellar population (SSP) models. This allows us to measure, for the first time, the low-mass end slope of the IMF, as well as stellar metallicity [M/H], [Mg/Fe], [Ti/Fe] and [Na/Fe] ratios, and study correlations between them and the DoR. Similarly to normal-sized galaxies, UCMGs with larger stellar masses have overall higher metallicities. We found a correlation between the low-mass end of the IMF slope and the DoR, that, however, breaks down for systems with a more extended SFH. An even stronger dependency is found between the IMF and the fraction of mass formed at high-z. At equal velocity dispersion and metallicity, galaxies with a higher DoR have a dwarf-richer IMF than that of low-DoR counterparts. This might indicate that the cosmic epoch and formation mechanisms influence the fragmentation of the star formation cloud and hence might be the explanation for IMF variations detected in massive ETGs. △ Less

Submitted 28 January, 2024; originally announced January 2024.

Comments: 16 pages, 11 figures, submitted to MNRAS

Ages, metallicity, and alpha-enhancement of the globular cluster populations in NGC 3311

Authors: Natalie Grasser, Magda Arnaboldi, Carlos Eduardo Barbosa, Chiara Spiniello, Lodovico Coccato, John Trevor Mendel

Abstract: Aims. We aim to investigate the stellar population properties, ages, and metal content of the globular clusters (GCs) in NGC 3311, the central galaxy of the Hydra I cluster, to better constrain its evolution history. Methods. We used integral-field spectroscopic data from the Multi-Unit Spectroscopic Explorer (MUSE) to identify 680 sources in the central region of NGC 3311 and extract their 1D spe… ▽ More Aims. We aim to investigate the stellar population properties, ages, and metal content of the globular clusters (GCs) in NGC 3311, the central galaxy of the Hydra I cluster, to better constrain its evolution history. Methods. We used integral-field spectroscopic data from the Multi-Unit Spectroscopic Explorer (MUSE) to identify 680 sources in the central region of NGC 3311 and extract their 1D spectra. An analysis of these sources in terms of morphologies, radial velocities, and emission lines allowed us to narrow down our selection to 49 bona fide GC candidates. We split these candidates into two groups depending on their projected distance to the galaxy center (R), namely inner (R<20arcsec) and outer (R>20arcsec) GCs. We stacked the extracted 1D spectra of the inner and outer GC populations to increase the signal-to-noise ratios (S/Ns) of the resulting spectra and hence allow full-spectrum fitting. In addition, we also created a stacked spectrum of all GCs in NGC 3311 and one of the two most central GC candidates. Using the code pPXF, we performed a stellar population analysis on the four stacked 1D spectra, obtaining mass-weighted integrated ages, metallicities, and [$α$/Fe] abundances. Results. All GCs are old, with ages >13.5 Gyr, and they have super-solar metallicities. Looking at the color distribution, we find that the inner ones tend to be redder and more metal rich than the outer ones. This is consistent with the two-phase formation scenario. Looking at the full-spectral fitting results, at face value the outer GCs have a larger [$α$/Fe] ratio, which is in line with what is found for the stars that dominate the surface brightness profile at the same radii. However, the values for outer and inner GCs are consistent within the uncertainties. △ Less

Submitted 15 December, 2023; originally announced December 2023.

Comments: Accepted for publication by A&A on November 15th 2023

Planetary nebulae as tracers of stellar population properties: unlocking their potential with integral-field spectroscopy

Authors: Ana Ennis, Johanna Hartke, Magda Arnaboldi, Claudia Pulsoni, Fuyan Bian, Chiara Spiniello

Abstract: Planetary nebulae (PNe) are essential tracers of the kinematics of the diffuse halo and intracluster light where stellar spectroscopy is unfeasible, due to their strong emission lines. However, that is not all they can reveal about the underlying stellar population. In recent years, it has also been found that PNe in the metal-poor halos of galaxies have different properties (specific frequency, l… ▽ More Planetary nebulae (PNe) are essential tracers of the kinematics of the diffuse halo and intracluster light where stellar spectroscopy is unfeasible, due to their strong emission lines. However, that is not all they can reveal about the underlying stellar population. In recent years, it has also been found that PNe in the metal-poor halos of galaxies have different properties (specific frequency, luminosity function), than PNe in the more metal-rich galaxy centers. A more quantitative understanding of the role of age and metallicity in these relations would turn PNe into valuable stellar-population tracers. In order to do that, a full characterization of PNe in regions where the stellar light can also be analysed in detail is necessary. In this work, we make use of integral-field spectroscopic data covering the central regions of galaxies, which allow us to measure both stellar ages and metallicities as well as to detect PNe. This analysis is fundamental to calibrate PNe as stellar population tracers and to push our understanding of galaxy properties at unprecedented galactocentric distances. △ Less

Submitted 15 November, 2023; originally announced November 2023.

Comments: Submitted to the Proceedings of IAU Symposium 384: Planetary Nebulae: a Universal Toolbox in the Era of Precision Astrophysics. Eds: O. De Marco, A. Zijlstra, R. Szczerba

Multi-band analysis of strong gravitationally lensed post-blue nugget candidates from the Kilo-Degree Survey

Authors: Rui Li, Nicola R. Napolitano, Linghua Xie, Ran Li, Xiaotong Guo, Alexey Sergeyev, Crescenzo Tortora, Chiara Spiniello, Alessandro Sonnenfeld Leon V. E. Koopmans, Diana Scognamiglio

Abstract: During the early stages of galaxy evolution, a significant fraction of galaxies undergo a transitional phase between the ``blue nugget" systems, which arise from the compaction of large, active star-forming disks, and the ``red nuggets", which are red and passive compact galaxies. These objects are typically only observable with space telescopes, and detailed studies of their size, mass, and stell… ▽ More During the early stages of galaxy evolution, a significant fraction of galaxies undergo a transitional phase between the ``blue nugget" systems, which arise from the compaction of large, active star-forming disks, and the ``red nuggets", which are red and passive compact galaxies. These objects are typically only observable with space telescopes, and detailed studies of their size, mass, and stellar population parameters have been conducted on relatively small samples. Strong gravitational lensing can offer a new opportunity to study them in detail, even with ground-based observations. In this study, we present the first 6 \textit{bona fide} sample of strongly lensed post-blue nugget (pBN) galaxies, which were discovered in the Kilo Degree Survey. By using the lensing-magnified luminosity from optical and near-infrared bands, we have derived robust structural and stellar population properties of the multiple images of the background sources. \rui{The pBN galaxies have very small sizes of $\rm R_{eff}<1.3$ kpc, high mass density inside 1 kpc of $ \rm \log (Σ_1/M_{\odot} \mathrm{kpc}^{-2})>9.3$, and low specific star formation rates of $\log (\mathrm{sSFR/Gyr})\lesssim0$, The size-mass and $Σ_1$-mass relations of this sample are consistent with those of the red nuggets, while their sSFR is close to the lower end of compact star-forming blue nugget systems at the same redshift, suggesting a clear evolutionary link between them. △ Less

Submitted 1 August, 2024; v1 submitted 6 November, 2023; originally announced November 2023.

Comments: Accepted for publication in APJ

Searching for strong gravitational lenses

Authors: Cameron Lemon, Frédéric Courbin, Anupreeta More, Paul Schechter, Raoul Cañameras, Ludovic Delchambre, Calvin Leung, Yiping Shu, Chiara Spiniello, Yashar Hezaveh, Jonas Klüter, Richard McMahon

Abstract: Strong gravitational lenses provide unique laboratories for cosmological and astrophysical investigations, but they must first be discovered - a task that can be met with significant contamination by other astrophysical objects and asterisms. Here we review strong lens searches, covering various sources (quasars, galaxies, supernovae, FRBs, GRBs, and GWs), lenses (early- and late-type galaxies, gr… ▽ More Strong gravitational lenses provide unique laboratories for cosmological and astrophysical investigations, but they must first be discovered - a task that can be met with significant contamination by other astrophysical objects and asterisms. Here we review strong lens searches, covering various sources (quasars, galaxies, supernovae, FRBs, GRBs, and GWs), lenses (early- and late-type galaxies, groups, and clusters), datasets (imaging, spectra, and lightcurves), and wavelengths. We first present the physical characteristics of the lens and source populations, highlighting relevant details for constructing targeted searches. Search techniques are described based on the main lensing feature that is required for the technique to work, namely one of: (i) an associated magnification, (ii) multiple spatially-resolved images, (iii) multiple redshifts, or (iv) a non-zero time delay between images. To use the current lens samples for science, and for the design of future searches, we list several selection biases that exist due to these discovery techniques. We conclude by discussing the future of lens searches in upcoming surveys and the new population of lenses that will be discovered. △ Less

Submitted 27 October, 2023; v1 submitted 20 October, 2023; originally announced October 2023.

Comments: 54 pages, 15 figures, submitted to Space Science Reviews, Topical Collection "Strong Gravitational Lensing", eds. J. Wambsganss et al

INSPIRE: INvestigating Stellar Population In RElics V. A catalogue of ultra-compact massive galaxies outside the local Universe and their degree of relicness

Authors: C. Spiniello, G. D'Ago, L. Coccato, J. Hartke, C. Tortora, A. Ferré-Mateu, C. Pulsoni, M. Cappellari, M. Maksymowicz-Maciata, M. Arnaboldi, D. Bevacqua, A. Gallazzi, L. K. Hunt, F. La Barbera, I. Martín-Navarro, N. R. Napolitano, M. Radovich, P. Saracco, D. Scognamiglio, M. Spavone, S. Zibetti

Abstract: This paper presents the third data release of the INvestigating Stellar Population In RElics (INSPIRE) project, comprising 52 ultra-compact massive galaxies (UCMGs) observed with the X-Shooter spectrograph. We measure integrated stellar velocity dispersion, [Mg/Fe] abundances, ages, and metallicities for all the INSPIRE objects. We thus infer star formation histories and confirm the existence of a… ▽ More This paper presents the third data release of the INvestigating Stellar Population In RElics (INSPIRE) project, comprising 52 ultra-compact massive galaxies (UCMGs) observed with the X-Shooter spectrograph. We measure integrated stellar velocity dispersion, [Mg/Fe] abundances, ages, and metallicities for all the INSPIRE objects. We thus infer star formation histories and confirm the existence of a degree of relicness (DoR), defined in terms of the fraction of stellar mass formed by $z=2$, the time at which a galaxy has assembled 75\% of its mass, and the final assembly time. Objects with a high DoR assembled their stellar mass at early epochs, while low-DoR objects show a non-negligible fraction of later-formed populations and hence a spread in ages and metallicities. A higher DoR correlates with larger [Mg/Fe], super-solar metallicity, and larger velocity dispersion values. The 52 UMCGs span a large range of DoR from 0.83 to 0.06, with 38 of them having formed more than 75\% of their mass by $z=2$. Of these, nine are extreme relics (DoR$>0.7$), since they formed the totality ($>99\%$) of their stellar mass by redshift $z=2$. The remaining 14 UCMGs cannot be considered relics, as they are characterised by more extended star formation histories. With INSPIRE, we built the first sizeable sample of relics outside the local Universe, up to $z\sim0.4$, increasing the number of confirmed relics by a factor of $>10$, and opening up an important window to explain the mass assembly of massive galaxies in the high-z Universe. △ Less

Submitted 14 November, 2023; v1 submitted 22 September, 2023; originally announced September 2023.

Comments: accepted for publication on MNRAS, 20 pages, 15 figures, 3 tables

Ultra diffuse galaxies in the Hydra I cluster from the LEWIS Project: Phase-Space distribution and globular cluster richness

Authors: Duncan Forbes, Jonah Gannon, Enrichetta Iodice, Michael Hilker, Goran Doll, Chiara Buttitta, Antonio La Marca, Magda Arnaboldi, Michele Cantiello, G. D'Ago, Jesus Falcon Barroso, Laura Greggio, Marco Gullieuszik, Johanna Hartke, Steffen Mieske, Marco Mirabile, Roberto Rampazzo, Marina Rejkuba, Marilena Spavone, Chiara Spiniello, Giulio Capasso

Abstract: Although ultra diffuse galaxies (UDGs) are found in large numbers in clusters of galaxies, the role of the cluster environment in shaping their low surface brightness and large sizes is still uncertain. Here we examine a sample of UDGs in the Hydra I cluster (D = 51 Mpc) with new radial velocities obtained as part of the LEWIS (Looking into the faintest with MUSE) project using VLT/MUSE data. Usin… ▽ More Although ultra diffuse galaxies (UDGs) are found in large numbers in clusters of galaxies, the role of the cluster environment in shaping their low surface brightness and large sizes is still uncertain. Here we examine a sample of UDGs in the Hydra I cluster (D = 51 Mpc) with new radial velocities obtained as part of the LEWIS (Looking into the faintest with MUSE) project using VLT/MUSE data. Using a phase-space, or infall diagnostic, diagram we compare the UDGs to other known galaxies in the Hydra I cluster and to UDGs in other clusters. The UDGs, along with the bulk of regular Hydra I galaxies, have low relative velocities and are located near the cluster core, and thus consistent with very early infall into the cluster. Combining with literature data, we do not find the expected trend of GC-rich UDGs associated with earlier infall times. This result suggests that quenching mechanisms other than cluster infall should be further considered, e.g. quenching by strong feedback or in cosmic sheets and filaments. Tidal stripping of GCs in the cluster environment also warrants further modelling. △ Less

Submitted 22 August, 2023; originally announced August 2023.

Comments: 6 pages, 2 figures, MNRAS, 525, 93

Looking into the faintEst WIth MUSE (LEWIS): on the nature of ultra-diffuse galaxies in the Hydra-I cluster.I. Project description and preliminary results

Authors: Enrichetta Iodice, Michael Hilker, Goran Doll, Marco Mirabile, Chiara Buttitta, Johanna Hartke, Steffen Mieske, Michele Cantiello, Giuseppe D'Ago, Duncan A. Forbes, Marco Gullieuszik, Marina Rejkuba, Marilena Spavone, Chiara Spiniello, Magda Arnaboldi, Enrico M. Corsini, Laura Greggio, Jesus Falcón-Barroso, Katja Fahrion, Jacopo Fritz, Antonio La Marca, Maurizio Paolillo, Maria Angela Raj, Roberto Rampazzo, Marc Sarzi , et al. (1 additional authors not shown)

Abstract: Looking into the faintEst WIth MUSE (LEWIS) is an ESO large observing programme aimed at obtaining the first homogeneous integral-field spectroscopic survey of 30 extremely low-surface brightness (LSB) galaxies in the Hydra I cluster of galaxies, with MUSE at ESO-VLT. The majority of LSB galaxies in the sample (22 in total) are ultra-diffuse galaxies (UDGs). The distribution of systemic velocities… ▽ More Looking into the faintEst WIth MUSE (LEWIS) is an ESO large observing programme aimed at obtaining the first homogeneous integral-field spectroscopic survey of 30 extremely low-surface brightness (LSB) galaxies in the Hydra I cluster of galaxies, with MUSE at ESO-VLT. The majority of LSB galaxies in the sample (22 in total) are ultra-diffuse galaxies (UDGs). The distribution of systemic velocities Vsys ranges between 2317 km/s and 5198 km/s and is centred on the mean velocity of Hydra I (Vsys = 3683 $\pm$ 46 km/s). Considering the mean velocity and the velocity dispersion of the cluster, 17 out of 20 targets are confirmed cluster members. To assess the quality of the data and demonstrate the feasibility of the science goals, we report the preliminary results obtained for one of the sample galaxies, UDG11. For this target, we derived the stellar kinematics, including the 2-dimensional maps of line-of-sight velocity and velocity dispersion, constrained age and metallicity, and studied the globular cluster (GC) population hosted by the UDG. Results are compared with the available measurements for UDGs and dwarf galaxies in literature. By fitting the stacked spectrum inside one effective radius, we find that UDG11 has a velocity dispersion $σ= 20 \pm 8$ km/s, it is old ($10\pm1$ Gyr), metal-poor ([M/H]=-1.17$\pm$0.11 dex) and has a total dynamical mass-to-light ratio M$/L_V\sim 14$, comparable to those observed for classical dwarf galaxies. The spatially resolved stellar kinematics maps suggest that UDG11 does not show a significant velocity gradient along either major or minor photometric axes. We find two GCs kinematically associated with UDG11. The estimated total number of GCs in UDG11, corrected for the spectroscopic completeness limit, is $N_{GC}= 5.9^{+2.2}_ {-1.8}$, which corresponds to a GC specific frequency of $S_N = 8.4^{+3.2}_{-2.7}$. △ Less

Submitted 22 August, 2023; originally announced August 2023.

Comments: Accepted for publication in Astronomy and Astrophysics

Journal ref: A&A 679, A69 (2023)

The elemental abundances of quiescent galaxies in the LEGA-C survey: the (non-)evolution of [α/Fe] from z = 0.75 to z = 0

Authors: Davide Bevacqua, Paolo Saracco, Francesco La Barbera, Giuseppe D'Ago, Roberto de Propris, Ignacio Ferreras, Anna Gallazzi, Anna Pasquali, Chiara Spiniello

Abstract: We measure the [$α$/Fe] abundances for 183 quiescent galaxies at z = 0.60 - 0.75 with stellar masses ranging 10.4 \leq log10 10.4 $\leq$ log10 (M$_*$ /M$_\odot$) $\leq$ 11.6 selected from the LEGA-C survey. We estimate [$α$/Fe] from the ratio of the spectral indices Mgb ($λ \sim 5177$ Å) and Fe4383, compared to predictions of simple stellar population models. We find that 91% of quiescents in our… ▽ More We measure the [$α$/Fe] abundances for 183 quiescent galaxies at z = 0.60 - 0.75 with stellar masses ranging 10.4 \leq log10 10.4 $\leq$ log10 (M$_*$ /M$_\odot$) $\leq$ 11.6 selected from the LEGA-C survey. We estimate [$α$/Fe] from the ratio of the spectral indices Mgb ($λ \sim 5177$ Å) and Fe4383, compared to predictions of simple stellar population models. We find that 91% of quiescents in our sample have supersolar [$α$/Fe], with an average value of [$α$/Fe] = +0.24 $\pm$ 0.01. We find no significant correlation between [$α$/Fe] and stellar metallicity, mass, velocity dispersion, and average formation time. Galaxies that formed the bulk of their stellar mass on time scales shorter than 1 Gyr follow the same [$α$/Fe] distribution as those which formed on longer time scales. In comparison to local early-type galaxies and to stacked spectra of quiescent galaxies at z = 0.38 and z = 0.07, we find that the average [$α$/Fe] has not changed between z = 0.75 and the present time. Our work shows that the vast majority of massive quiescent galaxies at z $\sim$ 0.7 are $α$-enhanced, and that no detectable evolution of the average [$α$/Fe] has taken place over the last $\sim$ 6.5 Gyr. △ Less

Submitted 7 August, 2023; originally announced August 2023.

Comments: 12 pages, 10 figures, 2 tables, 1 appendix

Stellar metallicity from optical and UV spectral indices: Test case for WEAVE-StePS

Authors: F. R. Ditrani, M. Longhetti, F. La Barbera, A. Iovino, L. Costantin, S. Zibetti, A. Gallazzi, M. Fossati, J. Angthopo, Y. Ascasibar, B. Poggianti, P. Sánchez-Blázquez, M. Balcells, M. Bianconi, M. Bolzonella, L. P. Cassarà, O. Cucciati, G. Dalton, A. Ferré-Mateu, R. García-Benito, B. Granett, M. Gullieuszik, A. Ikhsanova, S. Jin, J. H. Knapen , et al. (13 additional authors not shown)

Abstract: The upcoming generation of optical spectrographs on four meter-class telescopes, with their huge multiplexing capabilities, excellent spectral resolution, and unprecedented wavelength coverage, will provide high-quality spectra for thousands of galaxies. These data will allow us to examine of the stellar population properties at intermediate redshift, an epoch that remains unexplored by large and… ▽ More The upcoming generation of optical spectrographs on four meter-class telescopes, with their huge multiplexing capabilities, excellent spectral resolution, and unprecedented wavelength coverage, will provide high-quality spectra for thousands of galaxies. These data will allow us to examine of the stellar population properties at intermediate redshift, an epoch that remains unexplored by large and deep surveys. We assess our capability to retrieve the mean stellar metallicity in galaxies at different redshifts and S/N, while simultaneously exploiting the UV and optical rest-frame wavelength coverage. The work is based on a comprehensive library of spectral templates of stellar populations, covering a wide range of age and metallicity values and built assuming various SFHs. We simulated realistic observations of a large sample of galaxies carried out with WEAVE at the WHT at different redshifts and S/N values. We measured all the reliable indices on the simulated spectra and on the comparison library. We then adopted a Bayesian approach to obtain the probability distribution of stellar metallicity. The analysis of the spectral indices has shown how some mid-UV indices can provide reliable constraints on stellar metallicity, along with optical indicators. The analysis of the mock observations has shown that even at S/N=10, the metallicity can be derived within 0.3 dex, in particular, for stellar populations older than 2 Gyr. Our results are in good agreement with other theoretical and observational works in the literature and show how the UV indicators can be advantageous in constraining metallicities. This is very promising for the upcoming surveys carried out with new, highly multiplexed, large-field spectrographs, such as StePS at the WEAVE and 4MOST, which will provide spectra of thousands of galaxies covering large spectral ranges at relatively high S/N. △ Less

Submitted 4 August, 2023; originally announced August 2023.

Comments: 16 pages, 14 figures. Submitted 31/03/2023, Accepted 20/07/2023

Journal ref: A&A 677, A93 (2023)

WEAVE-StePS. A stellar population survey using WEAVE at WHT

Authors: A. Iovino, B. M. Poggianti, A. Mercurio, M. Longhetti, M. Bolzonella, G. Busarello, M. Gullieuszik, F. LaBarbera, P. Merluzzi, L. Morelli, C. Tortora, D. Vergani, S. Zibetti, C. P. Haines, L. Costantin, F. R. Ditrani, L. Pozzetti, J. Angthopo, M. Balcells, S. Bardelli, C. R. Benn, M. Bianconi, L. P. Cassarà, E. M. Corsini, O. Cucciati , et al. (22 additional authors not shown)

Abstract: The upcoming new generation of optical spectrographs on four-meter-class telescopes will provide valuable opportunities for forthcoming galaxy surveys through their huge multiplexing capabilities, excellent spectral resolution, and unprecedented wavelength coverage. WEAVE is a new wide-field spectroscopic facility mounted on the 4.2 m William Herschel Telescope in La Palma. WEAVE-StePS is one of t… ▽ More The upcoming new generation of optical spectrographs on four-meter-class telescopes will provide valuable opportunities for forthcoming galaxy surveys through their huge multiplexing capabilities, excellent spectral resolution, and unprecedented wavelength coverage. WEAVE is a new wide-field spectroscopic facility mounted on the 4.2 m William Herschel Telescope in La Palma. WEAVE-StePS is one of the five extragalactic surveys that will use WEAVE during its first five years of operations. It will observe galaxies using WEAVE MOS (~950 fibres across a field of view of ~3 deg2 on the sky) in low-resolution mode (R~5000, spanning the wavelength range 3660-9590 AA). WEAVE-StePS will obtain high-quality spectra (S/N ~ 10 per AA at R~5000) for a magnitude-limited (I_AB = 20.5) sample of ~25,000 galaxies, the majority selected at z>=0.3. The survey goal is to provide precise spectral measurements in the crucial interval that bridges the gap between LEGA-C and SDSS data. The wide area coverage of ~25 deg2 will enable us to observe galaxies in a variety of environments. The ancillary data available in each observed field (including X-ray coverage, multi-narrow-band photometry and spectroscopic redshift information) will provide an environmental characterisation for each observed galaxy. This paper presents the science case of WEAVE-StePS, the fields to be observed, the parent catalogues used to define the target sample, and the observing strategy chosen after a forecast of the expected performance of the instrument for our typical targets. WEAVE-StePS will go back further in cosmic time than SDSS, extending its reach to encompass more than ~6 Gyr, nearly half of the age of the Universe. The spectral and redshift range covered by WEAVE-StePS will open a new observational window by continuously tracing the evolutionary path of galaxies in the largely unexplored intermediate-redshift range. △ Less

Submitted 14 February, 2023; originally announced February 2023.

Comments: 15 pages, 9 figures, A&A in press

Journal ref: A&A 672, A87 (2023)

INSPIRE: INvestigating Stellar Population In RElics IV. The Initial Mass Function slope in relics

Authors: I. Martin-Navarro, C. Spiniello, C. Tortora, L. Coccato, G. D'Ago, A. Ferre-Mateu, C. Pulsoni, J. Hartke, M. Arnaboldi, L. Hunt, N. R. Napolitano, D. Scognamiglio, M. Spavone

Abstract: In the last decade, growing evidence has emerged supporting a non-universal stellar Initial Mass Function (IMF) in massive galaxies, with a larger number of dwarf stars with respect to the Milky-Way (bottom-heavy IMF). However, a consensus about the mechanisms that cause IMF variations is yet to be reached. Recently, it has been suggested that stars formed early-on in cosmic time, via a star forma… ▽ More In the last decade, growing evidence has emerged supporting a non-universal stellar Initial Mass Function (IMF) in massive galaxies, with a larger number of dwarf stars with respect to the Milky-Way (bottom-heavy IMF). However, a consensus about the mechanisms that cause IMF variations is yet to be reached. Recently, it has been suggested that stars formed early-on in cosmic time, via a star formation burst, could be characterised by a bottom-heavy IMF. A promising way to confirm this is to use relics, ultra-compact massive galaxies, almost entirely composed by these "pristine" stars. The INSPIRE Project aims at assembling a large sample of confirmed relics, that can serve as laboratory to investigate on the conditions of star formation in the first 1-3 Gyr of the Universe. In this third INSPIRE paper, we build a high signal-to-noise spectrum from five relics and one from five galaxies with similar sizes, masses, and kinematical properties, but characterised by a more extended star formation history (non-relics). Our detailed stellar population analysis suggests a systematically bottom-heavier IMF slope for relics than for non-relics, adding new observational evidence for the non-universality of the IMF at various redshifts and further supporting the above proposed physical scenario. △ Less

Submitted 13 February, 2023; originally announced February 2023.

Comments: Accepted for publication in MNRAS. 8 pages, 5 figures

INSPIRE: INvestigating Stellar Population In RElics III. Second data release (DR2): testing the systematics on the stellar velocity dispersion

Authors: G. D'Ago, C. Spiniello, L. Coccato, C. Tortora, F. La Barbera, M. Arnaboldi, D. Bevacqua, A. Ferré-Mateu, A. Gallazzi, J. Hartke, L. K. Hunt, I. Martín-Navarro, N. R. Napolitano, C. Pulsoni, M. Radovich, P. Saracco, D. Scognamiglio, S. Zibetti

Abstract: This is the second data release (DR2) of the INvestigating Stellar Population In RElics (INSPIRE) project, comprising 21 new systems with observations completed before March 2022. For each system, we release four one-dimensional (1D) spectra to the ESO Science Archive, one spectrum for each arm of the X-Shooter spectrograph. In this paper, we focus on the line-of-sight velocity distribution, measu… ▽ More This is the second data release (DR2) of the INvestigating Stellar Population In RElics (INSPIRE) project, comprising 21 new systems with observations completed before March 2022. For each system, we release four one-dimensional (1D) spectra to the ESO Science Archive, one spectrum for each arm of the X-Shooter spectrograph. In this paper, we focus on the line-of-sight velocity distribution, measuring integrated stellar velocity dispersions from the spectra, and assessing their robustness and the associated uncertainties. For each of the 21 new systems, we systematically investigated the effect of the parameters and set-ups of the full spectral fitting on the stellar velocity dispersion ($σ$) measurements. In particular, we tested how $σ$ changes when several parameters of the fit as well as the resolution and spectral coverage of the input spectra are varied. We found that the effect that causes the largest systematic uncertainties on $σ$ is the wavelength range used for the fit, especially for spectra with a lower signal-to-noise ratio (S/N $\leq$ 30). When using blue wavelengths (UVB arm) one generally underestimates the velocity dispersion (by $\sim$15 km/s). The values obtained from the near-IR (NIR) arm present a larger scatter because the quality of the spectra is lower. We finally compared our results with those in literature, finding a very good agreement overall. Joining results obtained in DR1 with those presented here, INSPIRE contains 40 ultra-compact massive galaxies, corresponding to 75% of the whole survey. By plotting these systems in a stellar mass-velocity dispersion diagram, we identify at least four highly reliable relic candidates among the new systems. Their velocity dispersion is larger than that of normal-sized galaxies of similar stellar mass. △ Less

Submitted 10 February, 2023; originally announced February 2023.

Comments: Accepted for publication, and in press on A&A

Journal ref: A&A 672, A17 (2023)

The star formation history and the nature of the mass-metallicity relation of passive galaxies at 1.0<z<1.4 from VANDELS

Authors: Paolo Saracco, Francesco La Barbera, Roberto De Propris, Davide Bevacqua, Danilo Marchesini, Gabriella De Lucia, Fabio Fontanot, Michaela Hirschmann, Mario Nonino, Anna Pasquali, Chiara Spiniello, Crescenzo Tortora

Abstract: We derived stellar ages and metallicities [Z/H] for $\sim$70 passive early type galaxies (ETGs) selected from VANDELS survey over the redshift range 1.0$<$$z$$<$1.4 and stellar mass range 10$<$log(M$_*$/M$_\odot$)$<$11.6. We find significant systematics in their estimates depending on models and wavelength ranges considered. Using the full-spectrum fitting technique, we find that both [Z/H] and ag… ▽ More We derived stellar ages and metallicities [Z/H] for $\sim$70 passive early type galaxies (ETGs) selected from VANDELS survey over the redshift range 1.0$<$$z$$<$1.4 and stellar mass range 10$<$log(M$_*$/M$_\odot$)$<$11.6. We find significant systematics in their estimates depending on models and wavelength ranges considered. Using the full-spectrum fitting technique, we find that both [Z/H] and age increase with mass as for local ETGs. Age and metallicity sensitive spectral indices independently confirm these trends. According to EMILES models, for 67 per cent of the galaxies we find [Z/H]$>$0.0, a percentage which rises to $\sim$90 per cent for log(M$_*$/M$_\odot$)$>$11 where the mean metallicity is [Z/H]=0.17$\pm$0.1. A comparison with homogeneous measurements at similar and lower redshift does not show any metallicity evolution over the redshift range 0.0<z<1.4. The derived star formation (SF) histories show that the stellar mass fraction formed at early epoch increases with the mass of the galaxy. Galaxies with log(M$_*$/M$_\odot$)$>$11.0 host stellar populations with [Z/H]>0.05, formed over short timescales ($Δ{t50}$$<$1 Gyr) at early epochs (t$_{form}$$<$2 Gyr), implying high star formation rates (SFR$>$100 M$_\odot$/yr) in high mass density regions (log($Σ_{1kpc}$)$>$10 M$_\odot$/kpc$^2$). This sharp picture tends to blur at lower masses: log(M$_*$/M$_\odot$)$\sim$10.6 galaxies can host either old stars with [Z/H]$<$0.0 or younger stars with [Z/H]$>$0.0, depending on the duration ($Δ{t50}$) of the SF. The relations between galaxy mass, age and metallicities are therefore largely set up ab initio as part of the galaxy formation process. Mass, SFR and SF time-scale all contribute to shape up the stellar mass-metallicity relation with the mass that modulates metals retention. △ Less

Submitted 23 January, 2023; originally announced January 2023.

Comments: 18 pages + Appendix, 16 figures, 5 tables. Accepted for publication in MNRAS

Strong Lensing by Galaxies

Authors: A. J. Shajib, G. Vernardos, T. E. Collett, V. Motta, D. Sluse, L. L. R. Williams, P. Saha, S. Birrer, C. Spiniello, T. Treu

Abstract: Strong gravitational lensing at the galaxy scale is a valuable tool for various applications in astrophysics and cosmology. The primary uses of galaxy-scale lensing are to study elliptical galaxies' mass structure and evolution, constrain the stellar initial mass function, and measure cosmological parameters. Since the discovery of the first galaxy-scale lens in the 1980s, this field has made sign… ▽ More Strong gravitational lensing at the galaxy scale is a valuable tool for various applications in astrophysics and cosmology. The primary uses of galaxy-scale lensing are to study elliptical galaxies' mass structure and evolution, constrain the stellar initial mass function, and measure cosmological parameters. Since the discovery of the first galaxy-scale lens in the 1980s, this field has made significant advancements in data quality and modeling techniques. In this review, we describe the most common methods for modeling lensing observables, especially imaging data, as they are the most accessible and informative source of lensing observables. We then summarize the primary findings from the literature on the astrophysical and cosmological applications of galaxy-scale lenses. We also discuss the current limitations of the data and methodologies and provide an outlook on the expected improvements in both areas in the near future. △ Less

Submitted 6 April, 2025; v1 submitted 19 October, 2022; originally announced October 2022.

Comments: Published in Space Science Reviews, Topical Collection "Strong Gravitational Lensing", eds. J. Wambsganss et al. This version: accepted version

Journal ref: Space Sci Rev 220, 87 (2024)

TDCOSMO. XI. New lensing galaxy redshift and velocity dispersion measurements from Keck spectroscopy of eight lensed quasar systems

Authors: P. Mozumdar, C. D. Fassnacht, T. Treu, C. Spiniello, A. J. Shajib

Abstract: We have measured the redshifts and single-aperture velocity dispersions of eight lens galaxies using the data collected by the Echellette Spectrograph and Imager (ESI) and Low Resolution Imaging Spectrometer (LRIS) at W.M. Keck observatory on different observing nights spread over three years (2018-2020). These results, combined with other ancillary data, such as high-resolution images of the lens… ▽ More We have measured the redshifts and single-aperture velocity dispersions of eight lens galaxies using the data collected by the Echellette Spectrograph and Imager (ESI) and Low Resolution Imaging Spectrometer (LRIS) at W.M. Keck observatory on different observing nights spread over three years (2018-2020). These results, combined with other ancillary data, such as high-resolution images of the lens systems, and time delays, are necessary to increase the sample size of the quasar-galaxy lens systems for which the Hubble constant can be measured, using the time-delay strong lensing method, hence increasing the precision of its inference. Typically, the 2D spectra of the quasar-galaxy lens systems get spatially blended due to seeing by ground-based observations. As a result, the extracted lensing galaxy (deflector) spectra become significantly contaminated by quasar light, which affects the ability to extract meaningful information about the deflector. To account for spatial blending and extract less contaminated and higher signal-to-noise ratio (S/N) 1D spectra of the deflectors, a forward modeling method has been implemented. From the extracted spectra, we have measured redshifts using prominent absorption lines and single aperture velocity dispersions using the penalized pixel fitting code pPXF. In this paper, we report the redshifts and single aperture velocity dispersions of eight lens galaxies - J0147+4630, B0445+123, B0631+519, J0659+1629, J0818-2613, J0924+0219, J1433+6007, and J1817+2729. Among these systems, six do not have previously measured velocity dispersions; for the other two, our measurements are consistent with previously reported values. Additionally, we have measured the previously unknown redshifts of the deflectors in J0818-2613 and J1817+2729 to be $0.866 \pm 0.002$ and $0.408 \pm 0.002$, respectively. △ Less

Submitted 16 February, 2023; v1 submitted 28 September, 2022; originally announced September 2022.

Comments: 13 pages, 6 figures, 3 tables; accepted in A&A

Journal ref: A&A 672, A20 (2023)

Galaxy populations in the Hydra I cluster from the VEGAS survey II. The ultra-diffuse galaxy population

Authors: Antonio La Marca, Enrichetta Iodice, Michele Cantiello, Duncan A. Forbes, Marina Rejkuba, Michael Hilker, Magda Arnaboldi, Laura Greggio, Chiara Spiniello, Steffen Mieske, Aku Venhola, Marilena Spavone, Giuseppe D'Ago, Maria Angela Raj, Rossella Ragusa, Marco Mirabile, Roberto Rampazzo, Reynier Peletier, Maurizio Paolillo, Nelvy Choque Challapa, Pietro Schipani

Abstract: In this work, we extend the catalog of low-surface brightness (LSB) galaxies, including Ultra-Diffuse Galaxy (UDG) candidates, within $\approx 0.4R_{vir}$ of the Hydra I cluster of galaxies, based on deep images from the VST Early-type GAlaxy Survey (VEGAS). The new galaxies are found by applying an automatic detection tool and carrying out additional visual inspections of $g$ and $r$ band images.… ▽ More In this work, we extend the catalog of low-surface brightness (LSB) galaxies, including Ultra-Diffuse Galaxy (UDG) candidates, within $\approx 0.4R_{vir}$ of the Hydra I cluster of galaxies, based on deep images from the VST Early-type GAlaxy Survey (VEGAS). The new galaxies are found by applying an automatic detection tool and carrying out additional visual inspections of $g$ and $r$ band images. This led to the detection of 11 UDGs and 8 more LSB galaxies. For all of them, the cluster membership has been assessed using the color-magnitude relation derived for early-type giant and dwarf galaxies in Hydra I. The UDGs and new LSB galaxies found in Hydra I span a wide range of central surface brightness ($22.7 \lesssim μ_{0,g} \lesssim 26.5$ mag/arcsec$^2$), effective radius ($0.6 \lesssim R_e \lesssim 4.0$ kpc) and color ($0.4 \leq g-r \leq 0.9$ mag), and have stellar masses in the range $\sim 5\times 10^6 - 2\times 10^8$M$_{\odot}$. The 2D projected distribution of both galaxy types is similar to the spatial distribution of dwarf galaxies, with over-densities in the cluster core and north of the cluster centre. They have similar color distribution and comparable stellar masses to the red dwarf galaxies. Based on photometric selection, we identify a total of 9 globular cluster candidates associated to the UDGs and 4 to the LSB galaxies, with the highest number of candidates in an individual UDG being three. We find that there are no relevant differences between dwarfs, LSB galaxies and UDGs: the structural parameters (that is surface brightness, size, colors, n-index) and GCs content of the three classes have similar properties and trends. This finding is consistent with UDGs being the extreme LSB tail of the size-luminosity distribution of dwarfs in this environment. △ Less

Submitted 15 June, 2022; originally announced June 2022.

Comments: Accepted for publication in A&A. 30 pages, 22 figures

Journal ref: A&A 665, A105 (2022)

STRIDES: Automated uniform models for 30 quadruply imaged quasars

Authors: T. Schmidt, T. Treu, S. Birrer, A. J. Shajib, C. Lemon, M. Millon, D. Sluse, A. Agnello, T. Anguita, M. W. Auger-Williams, R. G. McMahon, V. Motta, P. Schechter, C. Spiniello, I. Kayo, F. Courbin, S. Ertl, C. D. Fassnacht, J. A. Frieman, A. More, S. Schuldt, S. H. Suyu, M. Aguena, F. Andrade-Oliveira, J. Annis , et al. (46 additional authors not shown)

Abstract: Gravitational time delays provide a powerful one step measurement of $H_0$, independent of all other probes. One key ingredient in time delay cosmography are high accuracy lens models. Those are currently expensive to obtain, both, in terms of computing and investigator time (10$^{5-6}$ CPU hours and $\sim$ 0.5-1 year, respectively). Major improvements in modeling speed are therefore necessary to… ▽ More Gravitational time delays provide a powerful one step measurement of $H_0$, independent of all other probes. One key ingredient in time delay cosmography are high accuracy lens models. Those are currently expensive to obtain, both, in terms of computing and investigator time (10$^{5-6}$ CPU hours and $\sim$ 0.5-1 year, respectively). Major improvements in modeling speed are therefore necessary to exploit the large number of lenses that are forecast to be discovered over the current decade. In order to bypass this roadblock, building on the work by Shajib et al. (2019), we develop an automated modeling pipeline and apply it to a sample of 30 quadruply imaged quasars and one lensed compact galaxy, observed by the Hubble Space Telescope in multiple bands. Our automated pipeline can derive models for 30/31 lenses with few hours of human time and <100 CPU hours of computing time for a typical system. For each lens, we provide measurements of key parameters and predictions of magnification as well as time delays for the multiple images. We characterize the cosmography-readiness of our models using the stability of differences in Fermat potential (proportional to time delay) w.r.t. modeling choices. We find that for 10/30 lenses our models are cosmography or nearly cosmography grade (<3% and 3-5% variations). For 6/30 lenses the models are close to cosmography grade (5-10%). These results are based on informative priors and will need to be confirmed by further analysis. However, they are also likely to improve by extending the pipeline modeling sequence and options. In conclusion, we show that uniform cosmography grade modeling of large strong lens samples is within reach. △ Less

Submitted 9 June, 2022; originally announced June 2022.

Comments: 40 pages, 24 figures, 11 tables. Submitted to MNRAS

The halo of M105 and its group environment as traced by planetary nebula populations: II. Using kinematics of single stars to unveil the presence of intragroup light around the Leo I galaxies NGC 3384 and M105

Authors: J. Hartke, M. Arnaboldi, O. Gerhard, L. Coccato, M. Merrifield, K. Kuijken, C. Pulsoni, A. Agnello, S. Bhattacharya, C. Spiniello, A. Cortesi, K. C. Freeman, N. R. Napolitano, A. J. Romanowsky

Abstract: M105 is an early-type galaxy in the nearby Leo I group, the closest galaxy group to contain all galaxy types and therefore an excellent environment to explore the low-mass end of intra-group light (IGL) assembly. We present a new extended kinematic survey of planetary nebulae (PNe) in M105 and the surrounding 30'x30' in the Leo I group with the Planetary Nebula Spectrograph. We use PNe as kinemati… ▽ More M105 is an early-type galaxy in the nearby Leo I group, the closest galaxy group to contain all galaxy types and therefore an excellent environment to explore the low-mass end of intra-group light (IGL) assembly. We present a new extended kinematic survey of planetary nebulae (PNe) in M105 and the surrounding 30'x30' in the Leo I group with the Planetary Nebula Spectrograph. We use PNe as kinematic tracers of the diffuse stellar light in the halo and IGL and employ Gaussian mixture models to separate contributions from the companion galaxy NGC 3384 and associate PNe with halo and IGL components around M105. We present a catalogue of 314 PNe and firmly associate 93 with NGC 3384 and 169 with M105. The PNe in M105 are further associated with its halo and the surrounding exponential envelope. We construct smooth velocity and velocity dispersion fields and calculate projected rotation, velocity dispersion, and $λ_R$ profiles for each component. Halo PNe exhibit declining velocity dispersion and rotation profiles, while the velocity dispersion and rotation of the exponential envelope increase notably at large radii. We identify three regimes with distinct kinematics that are linked to distinct stellar population properties: (i) the rotating core (within $1~R_\mathrm{eff}$) formed in situ and dominated by metal-rich ([M/H]~0) stars likely formed in situ, (ii) the halo from 1 to $7.5~R_\mathrm{eff}$ consisting of intermediate-metallicity stars ([M/H]>-1), either formed in situ or brought in through major mergers, and (iii) the exponential envelope reaching beyond our farthest data point at 16 $R_\mathrm{eff}$, predominately composed of metal-poor ([M/H]<-1) stars. The high velocity dispersion and moderate rotation of the latter are consistent with that measured for dwarf satellite galaxies in the Leo I group, indicating that the exponential envelope traces the transition to the IGL. △ Less

Submitted 21 January, 2022; originally announced January 2022.

Comments: Submitted to A&A, comments welcome. 20 pages, 14 figures, abstract abridged

Journal ref: A&A 663, A12 (2022)

Galaxy populations in the Hydra I cluster from the VEGAS survey I. Optical properties of a large sample of dwarf galaxies

Authors: Antonio La Marca, Reynier Peletier, Enrichetta Iodice, Maurizio Paolillo, Nelvy Choque Challapa, Aku Venhola, Duncan A. Forbes, Michele Cantiello, Michael Hilker, Marina Rejkuba, Magda Arnaboldi, Marilena Spavone, Giuseppe D'Ago, Maria Angela Raj, Rossella Ragusa, Marco Mirabile, Roberto Rampazzo, Chiara Spiniello, Steffen Mieske, Pietro Schipani

Abstract: At ~50 Mpc, the Hydra I cluster of galaxies is among the closest cluster in the z=0 Universe, and an ideal environment to study dwarf galaxy properties in a cluster environment. We exploit deep imaging data of the Hydra I cluster to construct a new photometric catalog of dwarf galaxies in the cluster core, which is then used to derive properties of the Hydra I cluster dwarf galaxies population as… ▽ More At ~50 Mpc, the Hydra I cluster of galaxies is among the closest cluster in the z=0 Universe, and an ideal environment to study dwarf galaxy properties in a cluster environment. We exploit deep imaging data of the Hydra I cluster to construct a new photometric catalog of dwarf galaxies in the cluster core, which is then used to derive properties of the Hydra I cluster dwarf galaxies population as well as to compare with other clusters. Moreover, we investigate the dependency of dwarf galaxy properties on their surrounding environment. The new Hydra I dwarf catalog contains 317 galaxies with luminosity between -18.5<$M_r$<-11.5 mag, a semi-major axis larger than ~200 pc (a=0.84 arcsec), of which 202 are new detections, previously unknown dwarf galaxies in the Hydra I central region. We estimate that our detection efficiency reaches 50% at the limiting magnitude $M_r$=-11.5 mag, and at the mean effective surface brightness $\overlineμ_{e,r}$=26.5 mag/$arcsec^2$. We present the standard scaling relations for dwarf galaxies and compare them with other nearby clusters. We find that there are no observational differences for dwarfs scaling relations in clusters of different sizes. We study the spatial distribution of galaxies, finding evidence for the presence of substructures within half the virial radius. We also find that mid- and high-luminosity dwarfs ($M_r$<-14.5 mag) become on average redder toward the cluster center, and that they have a mild increase in $R_e$ with increasing clustercentric distance, similar to what is observed for the Fornax cluster. No clear clustercentric trends are reported with surface brightness and Sérsic index. Considering galaxies in the same magnitude-bins, we find that for high and mid-luminosity dwarfs ($M_r$<-13.5 mag) the g-r color is redder for the brighter surface brightness and higher Sérsic n index objects. △ Less

Submitted 27 December, 2021; v1 submitted 1 December, 2021; originally announced December 2021.

Comments: Accepted for publication in A&A. 25 pages, 21 figures

Journal ref: A&A 659, A92 (2022)