Showing 1–50 of 126 results for author: Lusso, E

The accretion of quasars at the epoch of reionisation: $JWST$ catches the primeval monsters slowly feasting

Authors: B. Trefoloni, E. Nardini, S. Carniani, E. Lusso, A. Marconi, E. Parlanti, A. Sacchi, A. Shlentsova, M. Signorini, G. Risaliti, S. Zamora

Abstract: Quasars (QSOs) emit an enormous amount of light as a result of the accretion of gas onto supermassive black holes (SMBHs). Thanks to their luminosity, the most distant known QSOs allow us to trace the growth of SMBHs deep into the epoch of reionisation. In this work, we employed $JWST$/NIRSpec observations of eight luminous (log$(L_{3000\,A^{\circ}}/(erg \, s^{-1}))>$45.7) QSOs at $z\geq$5.9 to co… ▽ More Quasars (QSOs) emit an enormous amount of light as a result of the accretion of gas onto supermassive black holes (SMBHs). Thanks to their luminosity, the most distant known QSOs allow us to trace the growth of SMBHs deep into the epoch of reionisation. In this work, we employed $JWST$/NIRSpec observations of eight luminous (log$(L_{3000\,A^{\circ}}/(erg \, s^{-1}))>$45.7) QSOs at $z\geq$5.9 to constrain their accretion properties, namely black hole mass, accretion disc (AD) luminosity, and Eddington ratio ($M_{BH}$, $L_{AD}$, $λ_{Edd}$), by fitting the rest-frame UV and optical emission with different AD models. This method provided self-consistent measurements of both $M_{BH}$ and $L_{AD}$. The uncertainties on $M_{BH}$ and $L_{AD}$, obtained within the AD-modelling framework ($σ^{AD}_{M_{BH}}\sim$0.2 dex; $σ^{AD}_{L_{AD}}\sim$0.1 dex), are significantly smaller than the systematic uncertainties associated with single-epoch $M_{BH}$ ($\sim$0.4 dex) and $L_{AD}$ derived via bolometric corrections ($\sim$0.2 dex). Based on these results, in our sample we found an average Eddington ratio of $\langle \log(λ_{Edd}) \rangle=-0.9$, with a dispersion of $\sim$0.2 dex. Assuming that our high-z QSOs are representative of optically-selected bright blue QSOs, we derive a fraction of systems accreting above the Eddington limit of $\sim$0.2%. In conclusion, this work i) demonstrates the suitability of $JWST$ to test AD models on high-redshift ($z\gtrsim$4) QSOs, thanks to the large NIRSpec spectral coverage; ii) shows that AD modelling can yield robust $M_{\rm BH}$ and $L_{\rm AD}$ measurements, with smaller uncertainties than the typical calibrations; and iii) provides compelling evidence for sub-Eddington accretion in bright high-$z$ QSOs, challenging the widespread paradigm of near- or super-Eddington accretion occurring in these sources. △ Less

Submitted 18 December, 2025; originally announced December 2025.

Comments: 19 pages, 8 figures. Submitted to A&A

Cosmic Duets I. High-spatial resolution spectroscopy of dual and lensed AGN with MUSE

Authors: M. Scialpi, F. Mannucci, Q. D'Amato, C. Marconcini, G. Cresci, A. Marconi, L. Ulivi, M. Fumagalli, P. Rosati, G. Tozzi, M. V. Zanchettin, E. Cataldi, L. Battistini, E. Bertola, C. Bracci, S. Carniani, M. Ceci, A. Chakraborty, C. Cicone, A. Ciurlo, A. De Rosa, G. Di Rosa, A. Feltre, M. Ginolfi, I. Lamperti , et al. (12 additional authors not shown)

Abstract: We present the first-year results of the MUSE Large Program "Cosmic Duets", aimed at obtaining adaptive-optics assisted MUSE observations with an angular resolution of 0.1"-0.2", providing integral-field spectroscopy of sub-arcsec separation dual and lensed active galactic nuclei (AGN) candidates. These observations reveal previously unexplored properties of dual and lensed systems, key to underst… ▽ More We present the first-year results of the MUSE Large Program "Cosmic Duets", aimed at obtaining adaptive-optics assisted MUSE observations with an angular resolution of 0.1"-0.2", providing integral-field spectroscopy of sub-arcsec separation dual and lensed active galactic nuclei (AGN) candidates. These observations reveal previously unexplored properties of dual and lensed systems, key to understanding galaxy evolution, black hole mergers, and strong-lensing modeling. Targets were selected using the Gaia Multi-Peak (GMP) technique, which identifies pairs of point-like sources with separations below 0.8" in the Gaia catalog. MUSE spatially resolved spectroscopy provides redshifts, ionization diagnostics, and absorption systems along the line of sight. We report results for 30 GMP-selected targets at z=0.5-3.5. All systems show at least two spatially resolved components. Nineteen objects are confirmed as AGN multiplets, including 6 dual AGN, 10 doubly-lensed quasars, and 3 quadruply-lensed systems, while the remaining 11 correspond to alignments with foreground stars. Among spectroscopically confirmed dual AGN in the literature, 24 pairs have separations below 7 kpc, and our sample accounts for 25% of them. We study dual and lensed AGN distributions as a function of redshift, magnitude, and projected separation, and find that bright systems (J<16.5) are dominated by lensed quasars, whereas the fraction of dual AGN increases at fainter magnitudes. This first-year sample demonstrates the high efficiency of GMP pre-selection combined with MUSE spectroscopy. The full program, targeting 150 systems, will enable statistical studies of dual AGN incidence and detailed constraints on mass distribution in strong-lensing galaxies. △ Less

Submitted 12 December, 2025; originally announced December 2025.

Comments: 20 pages, 14 figures

Euclid Quick Data Release (Q1): Euclid spectroscopy of QSOs. 1. Identification and redshift determination of 3500 bright QSOs

Authors: Euclid Collaboration, Y. Fu, R. Bouwens, K. I. Caputi, D. Vergani, M. Scialpi, B. Margalef-Bentabol, L. Wang, M. Bolzonella, M. Banerji, E. Bañados, A. Feltre, Y. Toba, J. Calhau, F. Tarsitano, P. A. C. Cunha, A. Humphrey, G. Vietri, F. Mannucci, S. Bisogni, F. Ricci, H. Landt, L. Spinoglio, T. Matamoro Zatarain, D. Stern , et al. (331 additional authors not shown)

Abstract: The slitless spectroscopy mode of the NISP onboard Euclid has enabled efficient spectroscopy of objects within a large FoV. We present a large and homogeneous sample of bright quasars identified from the Euclid Quick Data Release (Q1) by combining high-purity candidate selections from Gaia and WISE with the NISP spectra. Through visual inspection of the Euclid spectra of these quasar candidates, w… ▽ More The slitless spectroscopy mode of the NISP onboard Euclid has enabled efficient spectroscopy of objects within a large FoV. We present a large and homogeneous sample of bright quasars identified from the Euclid Quick Data Release (Q1) by combining high-purity candidate selections from Gaia and WISE with the NISP spectra. Through visual inspection of the Euclid spectra of these quasar candidates, we identify approximately 3500 quasars with reliable redshifts at $0<z\lesssim 4.8$. We generate the first Euclid composite spectrum of quasars covering rest-frame NUV to NIR wavelengths without telluric lines, which will be pivotal to NIR quasar spectral analysis. We obtain an empirical spectroscopic depth of $J_{\rm E}\lesssim 21.5$ and $H_{\rm E}\lesssim 21.3$ at the sensitivity of the Wide Field Survey, beyond which the number of securely identified quasars declines sharply. We analyse VIS morphologies using Sersic and CAS metrics, and a deep-learning PSF fraction to track nuclear dominance. At low redshift ($z<0.5$), obvious host structures are common and a single Sersic model fits about half of the sources; at intermediate redshift ($0.5<z<2$), the nuclear component dominates, with 90% of the Sersic fits saturating at the upper index limit. In this intermediate redshift regime, $f_{\rm PSF}$ is available, and we use it as a more reliable compactness measure than the single-Sersic and CAS parameters to quantify nuclear versus host emission. We also explore the novel Euclid NIR colour space and discuss the role of these quasars in refining AGN selection techniques for future Euclid data releases. Our results highlight the potential of Euclid spectroscopy to advance quasar surveys and enable the construction of more complete AGN catalogues. The spectroscopic bright quasar catalogue of this work, and the composite quasar spectrum, will be available at https://cdsarc.cds.unistra.fr/. (abridged) △ Less

Submitted 9 December, 2025; originally announced December 2025.

Comments: 24 pages, 15 figures, 5 tables, submitted to A&A Euclid Quick Data Release (Q1) special issue

The Advanced X-ray Imaging Satellite Community Science Book

Authors: Michael Koss, Nafisa Aftab, Steven W. Allen, Roberta Amato, Hongjun An, Igor Andreoni, Timo Anguita, Riccardo Arcodia, Thomas Ayres, Matteo Bachetti, Maria Cristina Baglio, Arash Bahramian, Marco Balboni, Ranieri D. Baldi, Solen Balman, Aya Bamba, Eduardo Banados, Tong Bao, Iacopo Bartalucci, Antara Basu-Zych, Rebeca Batalha, Lorenzo Battistini, Franz Erik Bauer, Andy Beardmore, Werner Becker , et al. (373 additional authors not shown)

Abstract: The AXIS Community Science Book represents the collective effort of more than 500 scientists worldwide to define the transformative science enabled by the Advanced X-ray Imaging Satellite (AXIS), a next-generation X-ray mission selected by NASA's Astrophysics Probe Program for Phase A study. AXIS will advance the legacy of high-angular-resolution X-ray astronomy with ~1.5'' imaging over a wide 24'… ▽ More The AXIS Community Science Book represents the collective effort of more than 500 scientists worldwide to define the transformative science enabled by the Advanced X-ray Imaging Satellite (AXIS), a next-generation X-ray mission selected by NASA's Astrophysics Probe Program for Phase A study. AXIS will advance the legacy of high-angular-resolution X-ray astronomy with ~1.5'' imaging over a wide 24' field of view and an order of magnitude greater collecting area than Chandra in the 0.3-12 keV band. Combining sharp imaging, high throughput, and rapid response capabilities, AXIS will open new windows on virtually every aspect of modern astrophysics, exploring the birth and growth of supermassive black holes, the feedback processes that shape galaxies, the life cycles of stars and exoplanet environments, and the nature of compact stellar remnants, supernova remnants, and explosive transients. This book compiles over 140 community-contributed science cases developed by five Science Working Groups focused on AGN and supermassive black holes, galaxy evolution and feedback, compact objects and supernova remnants, stellar physics and exoplanets, and time-domain and multi-messenger astrophysics. Together, these studies establish the scientific foundation for next-generation X-ray exploration in the 2030s and highlight strong synergies with facilities of the 2030s, such as JWST, Roman, Rubin/LSST, SKA, ALMA, ngVLA, and next-generation gravitational-wave and neutrino networks. △ Less

Submitted 31 October, 2025; originally announced November 2025.

Comments: 595 pages, 225 figures

Euclid preparation. Predicting star-forming galaxy scaling relations with the spectral stacking code SpectraPyle

Authors: Euclid Collaboration, S. Quai, L. Pozzetti, M. Talia, C. Mancini, P. Cassata, L. Gabarra, V. Le Brun, M. Bolzonella, E. Rossetti, S. Kruk, B. R. Granett, C. Scarlata, M. Moresco, G. Zamorani, D. Vergani, X. Lopez Lopez, A. Enia, E. Daddi, V. Allevato, I. A. Zinchenko, M. Magliocchetti, M. Siudek, L. Bisigello, G. De Lucia , et al. (287 additional authors not shown)

Abstract: We introduce SpectraPyle, a versatile spectral stacking pipeline developed for the Euclid mission's NISP spectroscopic surveys, aimed at extracting faint emission lines and spectral features from large galaxy samples in the Wide and Deep Surveys. Designed for computational efficiency and flexible configuration, SpectraPyle supports the processing of extensive datasets critical to Euclid's non-cosm… ▽ More We introduce SpectraPyle, a versatile spectral stacking pipeline developed for the Euclid mission's NISP spectroscopic surveys, aimed at extracting faint emission lines and spectral features from large galaxy samples in the Wide and Deep Surveys. Designed for computational efficiency and flexible configuration, SpectraPyle supports the processing of extensive datasets critical to Euclid's non-cosmological science goals. We validate the pipeline using simulated spectra processed to match Euclid's expected final data quality. Stacking enables robust recovery of key emission lines, including Halpha, Hbeta, [O III], and [N II], below individual detection limits. However, the measurement of galaxy properties such as star formation rate, dust attenuation, and gas-phase metallicity are biased at stellar mass below log10(M*/Msol) ~ 9 due to the flux-limited nature of Euclid spectroscopic samples, which cannot be overcome by stacking. The SFR-stellar mass relation of the parent sample is recovered reliably only in the Deep survey for log10(M*/Msol) > 10, whereas the metallicity-mass relation is recovered more accurately over a wider mass range. These limitations are caused by the increased fraction of redshift measurement errors at lower masses and fluxes. We examine the impact of residual redshift contaminants that arises from misidentified emission lines and noise spikes, on stacked spectra. Even after stringent quality selections, low-level contamination (< 6%) has minimal impact on line fluxes due to the systematically weaker emission of contaminants. Percentile-based analysis of stacked spectra provides a sensitive diagnostic for detecting contamination via coherent spurious features at characteristic wavelengths. While our simulations include most instrumental effects, real Euclid data will require further refinement of contamination mitigation strategies. △ Less

Submitted 19 September, 2025; originally announced September 2025.

Comments: 17 pages, 21 figures, Submitted to A&A

The X-ray$-$UV Luminosity Relation of eROSITA Quasars

Authors: Andrea Sacchi, Guido Risaliti, Matilde Signorini, Emanuele Nardini, Elisabeta Lusso, Bartolomeo Trefoloni

Abstract: The non-linear relation between the UV and X-ray luminosity in quasars has been studied for decades. However, as we lack a comprehensive model able to explain it, its investigation still relies on observational efforts. This work focuses on optically selected quasars detected by eROSITA. We present the properties of the sources collected in the eROSITA early data release (eFEDS) and those resultin… ▽ More The non-linear relation between the UV and X-ray luminosity in quasars has been studied for decades. However, as we lack a comprehensive model able to explain it, its investigation still relies on observational efforts. This work focuses on optically selected quasars detected by eROSITA. We present the properties of the sources collected in the eROSITA early data release (eFEDS) and those resulting from the first six months of eROSITA all-sky survey (eRASS1). We focus on the subset of quasars bright enough in the optical/UV band to avoid an ''Eddington bias'' towards X-ray brighter-than-average spectral energy distributions. The final samples include 1,248 and 519 sources for eFEDS and eRASS1, up to redshift $z\approx3$ and $z\approx1.5$, respectively. We found that the X-ray$-$UV luminosity relation shows no significant evolution with redshift, and its slope is in perfect agreement with previous compilations of quasar samples. The intrinsic dispersion of the relation is about 0.2 dex, which is small enough for possible cosmological applications. However, the limited redshift range and statistics of the current samples do not allow us to obtain significant cosmological constraints yet. We show how this is going to change with the future releases of the eROSITA data. △ Less

Submitted 16 October, 2025; v1 submitted 1 August, 2025; originally announced August 2025.

Comments: 8 pages, 8 figures, 1 table, Accepted for publication on A&A

Journal ref: A&A 703, A273 (2025)

Quasar cosmology II: joint analyses with Cosmic Microwave Background

Authors: M. Benetti, G. Bargiacchi, G. Risaliti, S. Capozziello, E. Lusso, M. Signorini

Abstract: Currently, the increasing availability of accurate cosmological probes leads to the emergence of tensions between data on the one hand and between theoretical predictions and direct observations on the other. Moreover, after 25 years since the discovery of the accelerated expansion of the Universe has elected the $Λ$CDM model as the reference model, resolving shortcomings of the standard cosmologi… ▽ More Currently, the increasing availability of accurate cosmological probes leads to the emergence of tensions between data on the one hand and between theoretical predictions and direct observations on the other. Moreover, after 25 years since the discovery of the accelerated expansion of the Universe has elected the $Λ$CDM model as the reference model, resolving shortcomings of the standard cosmological model seems to be an unpostponed priority. Hence, it is key to test alternative models and investigate new cosmological probes at distances that range from the late to the early Universe, namely between the cosmic microwave background (CMB) and type Ia supernovae and baryonic acoustic oscillations (BAO) data. Bargiacchi et al. (2022) for the first time analysed dark energy (DE) models using quasars (QSOs) while also testing their consistency with BAO. Here, we carry on by exploring the compatibility of QSOs with both CMB data and dark energy survey measurements against the standard cosmological model and some DE extensions, such as the $w$CDM and Chevallier-Polarski-Linder parameterisations. We also consider an interacting dark matter and vacuum energy scenario, where vacuum energy perturbations affect the evolution of the matter growth rate in a decomposed Chaplygin gas model. We implement the QSO probe in Cobaya Markov chain Monte Carlo algorithm, using Botzmann solver codes as Cosmic Linear Anisotropy Solving System (CLASS) for the theory predictions. Our work shows that simple DE deviations from $Λ$CDM model do not reconcile the data and that only more complex models of interaction in the dark sector can succeed in solving the discrepancies of probes at all scales. △ Less

Submitted 26 June, 2025; originally announced June 2025.

Comments: 23 pages, 3 figures, accepted in Physics of Dark Universe

Euclid: The potential of slitless infrared spectroscopy: A z=5.4 quasar and new ultracool dwarfs

Authors: E. Bañados, V. Le Brun, S. Belladitta, I. Momcheva, D. Stern, J. Wolf, M. Ezziati, D. J. Mortlock, A. Humphrey, R. L. Smart, S. L. Casewell, A. Pérez-Garrido, B. Goldman, E. L. Martín, A. Mohandasan, C. Reylé, C. Dominguez-Tagle, Y. Copin, E. Lusso, Y. Matsuoka, K. McCarthy, F. Ricci, H. -W. Rix, H. J. A. Rottgering, J. -T. Schindler , et al. (204 additional authors not shown)

Abstract: We demonstrate the potential of Euclid's slitless spectroscopy to discover high-redshift (z>5) quasars and their main photometric contaminant, ultracool dwarfs. Sensitive infrared spectroscopy from space is able to efficiently identify both populations, as demonstrated by Euclid Near-Infrared Spectrometer and Photometer Red Grism (NISP RGE) spectra of the newly discovered z=5.404 quasar EUCL J1815… ▽ More We demonstrate the potential of Euclid's slitless spectroscopy to discover high-redshift (z>5) quasars and their main photometric contaminant, ultracool dwarfs. Sensitive infrared spectroscopy from space is able to efficiently identify both populations, as demonstrated by Euclid Near-Infrared Spectrometer and Photometer Red Grism (NISP RGE) spectra of the newly discovered z=5.404 quasar EUCL J181530.01+652054.0, as well as several ultracool dwarfs in the Euclid Deep Field North and the Euclid Early Release Observation field Abell 2764. The ultracool dwarfs were identified by cross-correlating their spectra with templates. The quasar was identified by its strong and broad CIII] and MgII emission lines in the NISP RGE 1206-1892 nm spectrum, and confirmed through optical spectroscopy from the Large Binocular Telescope. The NISP Blue Grism (NISP BGE) 926-1366 nm spectrum confirms CIV and CIII] emission. NISP RGE can find bright quasars at z~5.5 and z>7, redshift ranges that are challenging for photometric selection due to contamination from ultracool dwarfs. EUCL J181530.01+652054.0 is a high-excitation, broad absorption line quasar detected at 144 MHz by the LOw-Frequency Array (L144=4e25 W/Hz). The quasar has a bolometric luminosity of 3e12 Lsun and is powered by a 3.4e9 Msun black hole. The discovery of this bright quasar is noteworthy as fewer than one such object was expected in the ~20 deg2 surveyed. This finding highlights the potential and effectiveness of NISP spectroscopy in identifying rare, luminous high-redshift quasars, previewing the census of these sources that Euclid's slitless spectroscopy will deliver over about 14,000 deg2 of the sky. △ Less

Submitted 25 August, 2025; v1 submitted 16 June, 2025; originally announced June 2025.

Comments: Updated to match published version. Euclid NISP RGE quasar spectrum in Fig. 5 and NISP BGE spectrum in Appendix Fig. C1

Journal ref: Mon Not R Astron Soc (2025) 1088-1102

Are quasars reliable standard candles?

Authors: Elisabeta Lusso, Guido Risaliti, Emanuele Nardini

Abstract: In this paper we address the question whether the non-linear relation between the X-ray and UV emission of quasars can be used to derive their distances. In previous works of our group, we demonstrated that such a relation does not show any redshift evolution in its slope. The derived distances are in agreement with the standard flat $Λ$CDM model up to $z$$\sim$1.5, but they show significant devia… ▽ More In this paper we address the question whether the non-linear relation between the X-ray and UV emission of quasars can be used to derive their distances. In previous works of our group, we demonstrated that such a relation does not show any redshift evolution in its slope. The derived distances are in agreement with the standard flat $Λ$CDM model up to $z$$\sim$1.5, but they show significant deviations at higher redshifts. Yet, several authors suggested that this discrepancy is due to inconsistencies between the low- and high-redshift sources within the parent sample, or to a redshift evolution of the relation. Here, we discuss these issues through a quantitative comparison with supernova-derived distances in the common redshift range, complemented by simulations showing that all the claimed inconsistencies would naturally arise from any limitation of the cosmological model adopted for the data analysis, that is, from our ignorance of the true cosmology. We argue that the reliability of the method can only be based on a cosmology-independent evaluation of the hypothesis of non-evolution of the X-ray to UV relation at $z$>1.5, subsequent to a careful check of the sample selection and of the flux measurements for possible redshift-dependent systematic effects. Since we do not conceive any physical reason for a sudden change of the normalization of the relation at $z$>1.5, and we can exclude any severe systematic effect in the data selection and flux measurements, we conclude that the application of the X-ray to UV relation to cosmology is well motivated. To further strengthen this point, we need to achieve a better understanding of the physical process behind the observed relation and/or an independent observational proof possibly confirming the discrepancy with $Λ$CDM found with quasars, such as future supernova measurements at $z$$\sim$2 or higher. △ Less

Submitted 22 April, 2025; v1 submitted 2 April, 2025; originally announced April 2025.

Comments: 16 pages, 13 figures, accepted for publication in A&A

Journal ref: A&A 697, A108 (2025)

Explaining the UV to X-ray correlation in AGN within the framework of X-ray illumination of accretion discs

Authors: E. Kammoun, I. E. Papadakis, M. Dovčiak, E. Lusso, E. Nardini, G. Risaliti

Abstract: It is established that the ultraviolet (UV) and X-ray emissions in active galactic nuclei (AGN) are tightly correlated. This correlation is observed both in low- and high-redshift sources. In particular, observations of large samples of quasars revealed the presence of a non-linear correlation between UV and X-rays. The physical origin of this correlation is poorly understood. In this work, we exp… ▽ More It is established that the ultraviolet (UV) and X-ray emissions in active galactic nuclei (AGN) are tightly correlated. This correlation is observed both in low- and high-redshift sources. In particular, observations of large samples of quasars revealed the presence of a non-linear correlation between UV and X-rays. The physical origin of this correlation is poorly understood. In this work, we explore this observed correlation in the framework of the X-ray illumination of the accretion disc by a central source. We have shown in previous works that this model successfully explains the continuum UV/optical time delays, variability, and the broadband spectral energy distribution in AGN. We use this model to produce $150,000$ model SEDs assuming a uniform distribution of model parameters. We compute the corresponding UV ($ 2500~Å $) and X-ray (2 keV) monochromatic luminosities and select only the model data points that agree with the observed UV-to-X-ray correlation. Our results show that the X-ray illumination of accretion disc model can reproduce the observed correlation for a subset of model configurations with a non-uniform distribution of black hole mass ($M_{\rm BH}$), accretion rate ($\dot{m}/\dot{m}_{\rm Edd}$), and power transferred from the accretion disc to the corona ($L_{\rm transf}/L_{\rm disc}$). In addition, our results reveal the presence of a correlation between $M_{\rm BH}$ and $\dot{m}/\dot{m}_{\rm Edd}$, and between $\dot{m}/\dot{m}_{\rm Edd}$ and $L_{\rm transf}/L_{\rm disc}$, to explain the observed X-ray-UV correlation. We also present evidence based on observed luminosities supporting our findings. We finally discuss the implications of our results. △ Less

Submitted 26 March, 2025; originally announced March 2025.

Comments: Accepted for publication in A&A

Euclid Quick Data Release (Q1). Optical and near-infrared identification and classification of point-like X-ray selected sources

Authors: Euclid Collaboration, W. Roster, M. Salvato, J. Buchner, R. Shirley, E. Lusso, H. Landt, G. Zamorani, M. Siudek, B. Laloux, T. Matamoro Zatarain, F. Ricci, S. Fotopoulou, A. Ferré-Mateu, X. Lopez Lopez, N. Aghanim, B. Altieri, A. Amara, S. Andreon, N. Auricchio, H. Aussel, C. Baccigalupi, M. Baldi, A. Balestra, S. Bardelli , et al. (294 additional authors not shown)

Abstract: To better understand the role of active galactic nuclei (AGN) in galaxy evolution, it is crucial to achieve a complete and pure AGN census. X-ray surveys are key to this, but identifying their counterparts (CTPs) at other wavelengths remains challenging due to their larger positional uncertainties and limited availability of deeper, uniform ancillary data. Euclid is revolutionising this effort, of… ▽ More To better understand the role of active galactic nuclei (AGN) in galaxy evolution, it is crucial to achieve a complete and pure AGN census. X-ray surveys are key to this, but identifying their counterparts (CTPs) at other wavelengths remains challenging due to their larger positional uncertainties and limited availability of deeper, uniform ancillary data. Euclid is revolutionising this effort, offering extensive coverage of nearly the entire extragalactic sky, particularly in the near-infrared bands, where AGN are more easily detected. With the first Euclid Quick Data Release (Q1), we identifyed, classifyed, and determined the redshifts of Euclid CTPs to known point-like sources from major X-ray surveys, including XMM-Newton, Chandra, and eROSITA. Using Bayesian statistics, combined with machine learning (ML), we identify the CTPs to 11 286 X-ray sources from the three X-ray telescopes. For the large majority of 10 194 sources, the associations are unique, with the remaining $\sim$ 10% of multi-CTP cases equally split between XMM-Newton and eROSITA. ML is then used to distinguish between Galactic (8%) and extragalactic (92%) sources. We computed photo-zs using deep learning for the 8617 sources detected in the 10th data release of the DESI Legacy Survey, reaching an accuracy and a fraction of outliers of about 5%. Based on their X-ray luminosities, over 99% of CTPs identified as extragalactic are classified as AGN, most of which appear unobscured given their hardness ratios. With this paper, we release our catalogue, which includes identifiers, basic X-ray properties, the details of the associations, and additional features such as Galactic/extragalactic classifications and photometric/spectroscopic redshifts. We also provide probabilities for sub-selecting the sample based on purity and completeness, allowing users to tailor the sample according to their specific needs. △ Less

Submitted 9 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)', 24 pages, 22 figures. PICZL code (Roster et al. 2024) used for computing the photo-z, is also released

Low-Eddington ratio, changing-look active galactic nuclei: the case of NGC 4614

Authors: Elisabeta Lusso, Lapo Casetti, Marco Romoli, Lara Fossi, Emanuele Nardini, Emanuele Arra, Benedetta Barsi, Clarissa Calamai, Francesca Campani, Riccardo Capogrosso, Francesco Chiti Tegli, Riccardo Ciantini, Eirini Demertzi, Marina A. Gaitani, Asia Giudice, Alessia Gori, Lorenzo Graziani, Laura Macchiarini, Marianna Michelagnoli, Chiara Niccolai, Irene Parenti, Simone Pistolesi, Martina Rago, Ofelia Romani, Leonardo Sani , et al. (5 additional authors not shown)

Abstract: Active galactic nuclei (AGN) are known to be variable sources across the entire electromagnetic spectrum, in particular at optical/ultraviolet and X-ray energies. Over the past decades, a growing number of AGN have displayed type transitions: from type 1 to type 2 or viceversa within a few years or even several months. These galaxies have been commonly referred to as changing-look AGN (CLAGN). Her… ▽ More Active galactic nuclei (AGN) are known to be variable sources across the entire electromagnetic spectrum, in particular at optical/ultraviolet and X-ray energies. Over the past decades, a growing number of AGN have displayed type transitions: from type 1 to type 2 or viceversa within a few years or even several months. These galaxies have been commonly referred to as changing-look AGN (CLAGN). Here we report on a new CLAGN, NGC 4614, which transitioned from a type 1.9 to a type 2 state. NGC 4614 is a nearly face-on barred galaxy at redshift $z = 0.016$, classified as a low-luminosity AGN. Its central black hole has a mass of about $1.6\times 10^7 M_\odot$ and an Eddington ratio around 1 percent. We recently acquired optical spectra of NGC 4614 at the Telescopio Nazionale Galileo and the data clearly suggest that the broad H$α$ component has strongly dimmed, if not disappeared. A very recent Swift observation confirmed our current optical data, with the AGN weakened by almost a factor of 10 with respect to previous X-ray observations. Indeed, NGC 4614 had been also observed by Swift/XRT 6 times in 2011, when the source was clearly detected in all observations. By fitting the stack of the 2011 Swift observations we obtain a photon index of $Γ=1.3\pm0.3$ and an equivalent hydrogen column density of $N_{\rm H}$=$1.2\pm0.3$ $\times$10$^{22}$ cm$^{-2}$, indicating that NGC 4614 can be moderately absorbed in the X-rays. Although a significant change in the foreground gas absorption that may have obscured the broad line region cannot be entirely ruled out, the most likely explanation for our optical and X-ray data is that NGC 4614 is experiencing a change in the accretion state that reduces the radiative efficiency of the X-ray corona. △ Less

Submitted 24 February, 2025; originally announced February 2025.

Comments: 8 pages, 5 figures, accepted for publication in A&A

Journal ref: A&A 695, A269 (2025)

Euclid: The $r_{\rm b}$-$M_\ast$ relation as a function of redshift. I. The $5 \times 10^9 M_\odot$ black hole in NGC 1272

Authors: R. Saglia, K. Mehrgan, S. de Nicola, J. Thomas, M. Kluge, R. Bender, D. Delley, P. Erwin, M. Fabricius, B. Neureiter, S. Andreon, C. Baccigalupi, M. Baldi, S. Bardelli, D. Bonino, E. Branchini, M. Brescia, J. Brinchmann, A. Caillat, S. Camera, V. Capobianco, C. Carbone, J. Carretero, S. Casas, M. Castellano , et al. (126 additional authors not shown)

Abstract: Core ellipticals, massive early-type galaxies have an almost constant inner surface brightness profile. The size of the core region correlates with the mass of the finally merged black hole. Here we report the first Euclid-based dynamical mass determination of a supermassive black hole. We study the centre of NGC 1272, the second most luminous elliptical galaxy in the Perseus cluster… ▽ More Core ellipticals, massive early-type galaxies have an almost constant inner surface brightness profile. The size of the core region correlates with the mass of the finally merged black hole. Here we report the first Euclid-based dynamical mass determination of a supermassive black hole. We study the centre of NGC 1272, the second most luminous elliptical galaxy in the Perseus cluster, combining the Euclid VIS photometry coming from the Early Release Observations of the Perseus cluster with VIRUS spectroscopic observations at the Hobby-Eberly Telescope. The core of NGC 1272 is detected on the Euclid VIS image. Its size is $1.29\pm 0.07''$ or 0.45 kpc, determined by fitting PSF-convolved core-Sérsic and Nuker-law functions. The two-dimensional stellar kinematics of the galaxy is measured from the VIRUS spectra by deriving optimally regularized non-parametric line-of-sight velocity distributions. Dynamical models of the galaxy are constructed using our axisymmetric and triaxial Schwarzschild codes. We measure a black hole mass of $(5\pm3) \times 10^9 M_\odot$, in line with the expectation from the $M_{\rm BH}$-$r_{\rm b}$ correlation, but eight times larger than predicted by the $M_{\rm BH}$-$σ$ correlation (at $1.8σ$ significance). The core size, rather than the velocity dispersion, allows one to select galaxies harboring the most massive black holes. The spatial resolution, wide area coverage, and depth of the \Euclid (Wide and Deep) surveys allow us to find cores of passive galaxies larger than 2 kpc up to redshift 1. △ Less

Submitted 4 November, 2024; originally announced November 2024.

Comments: Accepted for publication in A&A

The near-infrared SED of blue quasars: what drives the evolution of the dusty torus?

Authors: Bartolomeo Trefoloni, Roberto Gilli, Elisabeta Lusso, Alessandro Marconi, Giovanni Mazzolari, Emanuele Nardini, Guido Risaliti, Matilde Signorini

Abstract: A fundamental ingredient in the unified model of active galactic nuclei (AGN) is the obscuring torus, whose innermost, hottest region dominates the near infrared (NIR) emission. Characterising the change in the torus properties and its interplay with the main AGN emission is key for our understanding of AGN physics, evolution and classification. Its covering factor ($CF$) is largely responsible fo… ▽ More A fundamental ingredient in the unified model of active galactic nuclei (AGN) is the obscuring torus, whose innermost, hottest region dominates the near infrared (NIR) emission. Characterising the change in the torus properties and its interplay with the main AGN emission is key for our understanding of AGN physics, evolution and classification. Its covering factor ($CF$) is largely responsible for the classification of AGN on the basis of the detection of broad emission lines. It is still not clear whether the torus properties evolve over time and how they relate with the accretion parameters of the nucleus. In this work, we aim at investigating the evolution of the NIR properties with the redshift ($z$) and the bolometric luminosity ($L_{\rm bol}$) of the AGN. To this end, we assembled a large dataset of $\sim$36,000 Type 1 AGN between $0.5<z<2.9$ and $45.0<\log(L_{\rm bol} / (\rm erg / s))<48.0$ with UV, optical and near-infrared photometry. We produced average spectral energy distributions (SED) in different bins of the $z-L_{\rm bol}$ parameter space to estimate how the NIR SED evolves according to these parameters. We find that the NIR luminosity decreases for increasing $L_{\rm bol}$ at any redshift. At the same, time the shape of the NIR SED in our sample is consistent with a non-evolution with $z$. As a consequence, all the explored proxies for the $CF$ exhibit significant anti-correlations with $L_{\rm bol}$, but not with $z$. Additionally, the $CF$ also shows a shallower anti-correlation with the Eddington ratio ($λ_{\rm Edd}$), yet current systematic uncertainties, as well as the limited dynamical range, do not allow us to precisely constrain the role of the Eddington ratio. Lastly, we derived the covering factor from the ratio between the NIR and optical luminosity and we employed it to set a lower limit for the X-ray obscuration at different redshifts. △ Less

Submitted 14 October, 2024; originally announced October 2024.

Comments: 22 pages, 15 figures

Journal ref: A&A 697, A223 (2025)

The MUSE Ultra Deep Field (MUDF) VII. Probing high-redshift gas structures in the surroundings of ALMA-identified massive dusty galaxies

Authors: A. Pensabene, M. Galbiati, M. Fumagalli, M. Fossati, I. Smail, M. Rafelski, M. Revalski, F. Arrigoni-Battaia, A. Beckett, S. Cantalupo, R. Dutta, E. Lusso, T. Lazeyras, G. Quadri, D. Tornotti

Abstract: We present new ALMA continuum and spectral observations of the MUSE Ultra Deep Field (MUDF), a $2\times 2$ arcmin$^2$ region with ultradeep multiwavelength imaging and spectroscopy hosting two bright $z\approx 3.22$ quasars used to study intervening gas structures in absorption. Through a blind search for dusty galaxies, we identified a total of seven high-confidence sources, six of which with sec… ▽ More We present new ALMA continuum and spectral observations of the MUSE Ultra Deep Field (MUDF), a $2\times 2$ arcmin$^2$ region with ultradeep multiwavelength imaging and spectroscopy hosting two bright $z\approx 3.22$ quasars used to study intervening gas structures in absorption. Through a blind search for dusty galaxies, we identified a total of seven high-confidence sources, six of which with secure spectroscopic redshifts. We estimate galaxy dust and stellar masses ($M_{\rm dust}\simeq 10^{7.8-8.6}\,M_{\odot}$, $M_{\star}\simeq 10^{10.2-10.7}\,M_{\odot}$), as well as star formation rates (${\rm SFR}\simeq 10^{1.2-2.0}\,M_{\odot}\,{\rm yr^{-1}} $) which show that most of these galaxies are massive and dust-obscured similar to coeval (sub-)millimeter galaxies. All six spectroscopically-confirmed galaxies are within $500~\rm km~s^{-1}$ of metal absorption lines observed in the quasar sightlines, corresponding to $100\%$ association rate. We also find that four of these galaxies belong to groups in which they are among the most massive members. Within the multiple group galaxies associated to the same absorption system, the ALMA sources are not always the closest in projection, but they are often aligned with the gaseous structures in velocity space. This suggests that these massive galaxies occupy the center of the potential well of the gas structures traced in absorption. However, albeit the low number density of sources identified with ALMA, our study may indicate that absorbers seem to infrequently originate in the inner circumgalactic medium of these galaxies. Instead, they appear to be better tracers of the gas distributed in the large-scale structure that host them. △ Less

Submitted 8 October, 2024; originally announced October 2024.

Comments: 13 pages, 9 figures, 1 Appendix. Submitted to A&A

Journal ref: A&A 696, A33 (2025)

Chandra Discovery of a Candidate Hyper-Luminous X-ray Source in MCG+11-11-032

Authors: Adi Foord, Francesca Civano, Julia M. Comerford, Martin Elvis, Giuseppina Fabbiano, Tingting Liu, Elisabeta Lusso, Stefano Marchesi, Mar Mezcua, Francisco Muller-Sanchez, Rebecca Nevin, Kristina Nyland

Abstract: We present a multi-wavelength analysis of MCG+11-11-032, a nearby AGN with the unique classification of both a binary and a dual AGN candidate. With new Chandra observations we aim to resolve any dual AGN system via imaging data, and search for signs of a binary AGN via analysis of the X-ray spectrum. Analyzing the Chandra spectrum, we find no evidence of previously suggested double-peaked Fe K… ▽ More We present a multi-wavelength analysis of MCG+11-11-032, a nearby AGN with the unique classification of both a binary and a dual AGN candidate. With new Chandra observations we aim to resolve any dual AGN system via imaging data, and search for signs of a binary AGN via analysis of the X-ray spectrum. Analyzing the Chandra spectrum, we find no evidence of previously suggested double-peaked Fe K$α$ lines; the spectrum is instead best fit by an absorbed powerlaw with a single Fe K$α$ line, as well as an additional line centered at $\approx$7.5 keV. The Chandra observation reveals faint, soft, and extended X-ray emission, possibly linked to low-level nuclear outflows. Further analysis shows evidence for a compact, hard source -- MCG+11-11-032 X2 -- located 3.27'' from the primary AGN. Modeling MCG+11-11-032 X2 as a compact source, we find that it is relatively luminous ($L_{\text{2$-$10 keV}} = 1.52_{-0.48}^{+0.96}\times 10^{41}$ erg s$^{-1}$), and the location is coincident with an compact and off-nuclear source resolved in Hubble Space Telescope infrared (F105W) and ultraviolet (F621M, F547M) bands. Pairing our X-ray results with a 144 MHz radio detection at the host galaxy location, we observe X-ray and radio properties similar to those of ESO 243-49 HLX-1, suggesting that MCG+11-11-032 X2 may be a hyper-luminous X-ray source. This detection with Chandra highlights the importance of a high-resolution X-ray imager, and how previous binary AGN candidates detected with large-aperture instruments benefit from high-resolution follow-up. Future spatially resolved optical spectra, and deeper X-ray observations, can better constrain the origin of MCG+11-11-032 X2. △ Less

Submitted 5 September, 2024; originally announced September 2024.

Comments: 16 pages, 7 figures, submitted to ApJ

High-definition imaging of a filamentary connection between a close quasar pair at z=3

Authors: Davide Tornotti, Michele Fumagalli, Matteo Fossati, Alejandro Benitez-Llambay, David Izquierdo-Villalba, Andrea Travascio, Fabrizio Arrigoni Battaia, Sebastiano Cantalupo, Alexander Beckett, Silvia Bonoli, Pratika Dayal, Valentina D'Odorico, Rajeshwari Dutta, Elisabeta Lusso, Celine Peroux, Marc Rafelski, Mitchell Revalski, Daniele Spinoso, Mark Swinbank

Abstract: Filaments connecting halos are a long-standing prediction of cold dark matter theories. We present a detection of the cosmic web emission connecting two quasar-host galaxies at redshift z ~3.22 in the MUSE Ultra Deep Field (MUDF). The very deep observations unlock a high-definition view of the filament morphology, a measure of the transition radius between the intergalactic and circumgalactic medi… ▽ More Filaments connecting halos are a long-standing prediction of cold dark matter theories. We present a detection of the cosmic web emission connecting two quasar-host galaxies at redshift z ~3.22 in the MUSE Ultra Deep Field (MUDF). The very deep observations unlock a high-definition view of the filament morphology, a measure of the transition radius between the intergalactic and circumgalactic medium, and the characterization of the surface brightness profiles along the filament and in the transverse direction. Through systematic comparisons with simulations, we validate the filaments' typical density predicted in the current cold dark-matter model. Our analysis of the MUDF field, an excellent laboratory for quantitatively studying filaments in emission, opens a new avenue to constrain the physical properties of the cosmic web and to trace the distribution of dark matter on large scales. △ Less

Submitted 29 January, 2025; v1 submitted 24 June, 2024; originally announced June 2024.

Comments: Published in Nature Astronomy on January 29th, 2025 (online); 4 main figures and 1 table; 7 extended data figures; 1 extended data table. See https://www.nature.com/articles/s41550-024-02463-w

Euclid preparation. Observational expectations for redshift z<7 active galactic nuclei in the Euclid Wide and Deep surveys

Authors: Euclid Collaboration, M. Selwood, S. Fotopoulou, M. N. Bremer, L. Bisigello, H. Landt, E. Bañados, G. Zamorani, F. Shankar, D. Stern, E. Lusso, L. Spinoglio, V. Allevato, F. Ricci, A. Feltre, F. Mannucci, M. Salvato, R. A. A. Bowler, M. Mignoli, D. Vergani, F. La Franca, A. Amara, S. Andreon, N. Auricchio, M. Baldi , et al. (238 additional authors not shown)

Abstract: We forecast the expected population of active galactic nuclei (AGN) observable in the Euclid Wide Survey (EWS) and Euclid Deep Survey (EDS). Starting from an X-ray luminosity function (XLF) we generate volume-limited samples of the AGN expected in the survey footprints. Each AGN is assigned an SED appropriate for its X-ray luminosity and redshift, with perturbations sampled from empirical distribu… ▽ More We forecast the expected population of active galactic nuclei (AGN) observable in the Euclid Wide Survey (EWS) and Euclid Deep Survey (EDS). Starting from an X-ray luminosity function (XLF) we generate volume-limited samples of the AGN expected in the survey footprints. Each AGN is assigned an SED appropriate for its X-ray luminosity and redshift, with perturbations sampled from empirical distributions. The photometric detectability of each AGN is assessed via mock observation of the assigned SED. We estimate 40 million AGN will be detectable in at least one band in the EWS and 0.24 million in the EDS, corresponding to surface densities of 2.8$\times$10$^{3}$ deg$^{-2}$ and 4.7$\times$10$^{3}$ deg$^{-2}$. Employing colour selection criteria on our simulated data we select a sample of 4.8$\times$10$^{6}$ (331 deg$^{-2}$) AGN in the EWS and 1.7$\times$10$^{4}$ (346 deg$^{-2}$) in the EDS, amounting to 10% and 8% of the AGN detectable in the EWS and EDS. Including ancillary Rubin/LSST bands improves the completeness and purity of AGN selection. These data roughly double the total number of selected AGN to comprise 21% and 15% of the detectable AGN in the EWS and EDS. The total expected sample of colour-selected AGN contains 6.0$\times$10$^{6}$ (74%) unobscured AGN and 2.1$\times$10$^{6}$ (26%) obscured AGN, covering $0.02 \leq z \lesssim 5.2$ and $43 \leq \log_{10} (L_{bol} / erg s^{-1}) \leq 47$. With this simple colour selection, expected surface densities are already comparable to the yield of modern X-ray and mid-infrared surveys of similar area. The relative uncertainty on our expectation for detectable AGN is 6.7% for the EWS and 12.5% for the EDS, driven by the uncertainty of the XLF. △ Less

Submitted 28 May, 2024; originally announced May 2024.

Comments: 36 pages, 21 figures, submitted to A&A

Journal ref: A&A 693, A250 (2025)

Euclid. I. Overview of the Euclid mission

Authors: Euclid Collaboration, Y. Mellier, Abdurro'uf, J. A. Acevedo Barroso, A. Achúcarro, J. Adamek, R. Adam, G. E. Addison, N. Aghanim, M. Aguena, V. Ajani, Y. Akrami, A. Al-Bahlawan, A. Alavi, I. S. Albuquerque, G. Alestas, G. Alguero, A. Allaoui, S. W. Allen, V. Allevato, A. V. Alonso-Tetilla, B. Altieri, A. Alvarez-Candal, S. Alvi, A. Amara , et al. (1115 additional authors not shown)

Abstract: The current standard model of cosmology successfully describes a variety of measurements, but the nature of its main ingredients, dark matter and dark energy, remains unknown. Euclid is a medium-class mission in the Cosmic Vision 2015-2025 programme of the European Space Agency (ESA) that will provide high-resolution optical imaging, as well as near-infrared imaging and spectroscopy, over about 14… ▽ More The current standard model of cosmology successfully describes a variety of measurements, but the nature of its main ingredients, dark matter and dark energy, remains unknown. Euclid is a medium-class mission in the Cosmic Vision 2015-2025 programme of the European Space Agency (ESA) that will provide high-resolution optical imaging, as well as near-infrared imaging and spectroscopy, over about 14,000 deg^2 of extragalactic sky. In addition to accurate weak lensing and clustering measurements that probe structure formation over half of the age of the Universe, its primary probes for cosmology, these exquisite data will enable a wide range of science. This paper provides a high-level overview of the mission, summarising the survey characteristics, the various data-processing steps, and data products. We also highlight the main science objectives and expected performance. △ Less

Submitted 24 September, 2024; v1 submitted 22 May, 2024; originally announced May 2024.

Comments: Accepted for publication in the A&A special issue`Euclid on Sky'

Journal ref: A&A 697, A1 (2025)

AGNfitter-rx: Modelling the radio-to-X-ray SEDs of AGNs

Authors: L. N. Martínez-Ramírez, G. Calistro Rivera, Elisabeta Lusso, F. E. Bauer, Emanuele Nardini, Johannes Buchner, Michael J. I. Brown, Juan C. B. Pineda, Matthew J. Temple, Manda Banerji, M. Stalevski, Joseph F. Hennawi

Abstract: We present new frontiers in the modelling of the spectral energy distributions (SED) of active galaxies by introducing the radio-to-X-ray fitting capabilities of the publicly available Bayesian code AGNfitter. The new code release, called AGNfitter-rx, models the broad-band photometry covering the radio, infrared (IR), optical, ultraviolet (UV) and X-ray bands consistently, using a combination of… ▽ More We present new frontiers in the modelling of the spectral energy distributions (SED) of active galaxies by introducing the radio-to-X-ray fitting capabilities of the publicly available Bayesian code AGNfitter. The new code release, called AGNfitter-rx, models the broad-band photometry covering the radio, infrared (IR), optical, ultraviolet (UV) and X-ray bands consistently, using a combination of theoretical and semi-empirical models of the AGN and host galaxy emission. This framework enables the detailed characterization of four physical components of the active nuclei: the accretion disk, the hot dusty torus, the relativistic jets/core radio emission, and the hot corona; alongside modeling three components within the host galaxy: stellar populations, cold dust, and the radio emission from the star-forming regions. Applying AGNfitter-rx to a diverse sample of 36 AGN SEDs at z<0.7 from the AGN SED ATLAS, we investigate and compare the performance of state-of-the-art torus and accretion disk emission models on fit quality and inferred physical parameters. We find that clumpy torus models that include polar winds and semi-empirical accretion disk templates including emission line features significantly increase the fit quality in 67% of the sources, by effectively reducing by $2σ$ fit residuals in the $1.5-5 μ\rm m$ and $0.7 μ\rm m$ regimes.We demonstrate that, by applying AGNfitter-rx on photometric data, we are able to estimate inclination and opening angles of the torus, consistent with spectroscopic classifications within the AGN unified model, as well as black hole mass estimates in agreement with virial estimates based on H$α$. The wavelength coverage and the flexibility for the inclusion of state-of-the-art theoretical models make AGNfitter-rx a unique tool for the further development of SED modelling for AGNs in present and future radio-to-X-ray galaxy surveys. △ Less

Submitted 28 May, 2024; v1 submitted 20 May, 2024; originally announced May 2024.

Comments: 20 pages, 10 figures, Accepted for publication by A&A

Quasars as standard candles VI: spectroscopic validation of the cosmological sample

Authors: Bartolomeo Trefoloni, Elisabeta Lusso, Emanuele Nardini, Guido Risaliti, Alessandro Marconi, Giada Bargiacchi, Andrea Sacchi, Matilde Signorini

Abstract: A sample of quasars has been recently assembled to investigate the non-linear relation between their monochromatic luminosities at 2500Å, and 2 keV and to exploit quasars as a new class of standardized candles. The use of this technique for cosmological purposes relies on the non-evolution with redshift of the UV-optical spectral properties of quasars, as well as on the absence of possible contami… ▽ More A sample of quasars has been recently assembled to investigate the non-linear relation between their monochromatic luminosities at 2500Å, and 2 keV and to exploit quasars as a new class of standardized candles. The use of this technique for cosmological purposes relies on the non-evolution with redshift of the UV-optical spectral properties of quasars, as well as on the absence of possible contaminants such as dust extinction and host-galaxy contribution. We address these possible issues by analysing the spectral properties of our cosmological quasar sample. We produced composite spectra in different bins of redshift and accretion parameters (black hole mass, bolometric luminosity), to investigate any possible evolution of the spectral properties of the continuum of the composites with these parameters. We found a remarkable similarity amongst the various stacked spectra. The overall shape of the continuum does not show any statistically significant trend with the accretion parameters nor with the redshift. The composite spectrum of our quasar sample is consistent with negligible levels of both intrinsic reddening (with a colour excess E(B-V)< 0.01) and host-galaxy emission (less than 10%) in the optical. We tested whether unaccounted dust extinction could explain the discrepancy between our cosmographic fit of the Hubble-Lemaitre diagram and the concordance ΛCDM model. The average colour excess required to solve the tension should increase with redshift up to unphysically high values (E(B-V)=0.1 at z>3) that would imply that the intrinsic emission of quasars is much bluer and more luminous than ever reported in observed spectra. The similarity of quasar spectra across the parameter space excludes a significant evolution of the average continuum properties with any of the explored parameters, confirming the reliability of our sample for cosmological applications. △ Less

Submitted 10 April, 2024; originally announced April 2024.

Comments: 24 pages, 18 figures, accepted for publication on A&A

Journal ref: A&A 689, A109 (2024)

The MUSE Ultra Deep Field (MUDF). V. Characterizing the Mass-Metallicity Relation for Low Mass Galaxies at $z\sim 1$-$2$

Authors: Mitchell Revalski, Marc Rafelski, Alaina Henry, Matteo Fossati, Michele Fumagalli, Rajeshwari Dutta, Norbert Pirzkal, Alexander Beckett, Fabrizio Arrigoni Battaia, Pratika Dayal, Valentina D'Odorico, Elisabeta Lusso, Kalina V. Nedkova, Laura J. Prichard, Casey Papovich, Celine Peroux

Abstract: Using more than 100 galaxies in the MUSE Ultra Deep Field with spectroscopy from the Hubble Space Telescope's Wide Field Camera 3 and the Very Large Telescope's Multi Unit Spectroscopic Explorer, we extend the gas-phase mass-metallicity relation (MZR) at $z\approx\,$1$\,$-$\,$2 down to stellar masses of M$_{\star}$ $\approx$ 10$^{7.5}$ M$_{\odot}$. The sample reaches six times lower in stellar mas… ▽ More Using more than 100 galaxies in the MUSE Ultra Deep Field with spectroscopy from the Hubble Space Telescope's Wide Field Camera 3 and the Very Large Telescope's Multi Unit Spectroscopic Explorer, we extend the gas-phase mass-metallicity relation (MZR) at $z\approx\,$1$\,$-$\,$2 down to stellar masses of M$_{\star}$ $\approx$ 10$^{7.5}$ M$_{\odot}$. The sample reaches six times lower in stellar mass and star formation rate (SFR) than previous HST studies at these redshifts, and we find that galaxy metallicities decrease to log(O/H) + 12 $\approx$ 7.8 $\pm$ 0.1 (15% solar) at log(M$_{\star}$/M$_{\odot}$) $\approx$ 7.5, without evidence of a turnover in the shape of the MZR at low masses. We validate our strong-line metallicities using the direct method for sources with [O III] $λ$4363 and [O III] $λ$1666 detections, and find excellent agreement between the techniques. The [O III] $λ$1666-based metallicities double existing measurements with S/N $\geq$ 5 for unlensed sources at $z~>$ 1, validating the strong-line calibrations up to $z \sim$2.5. We confirm that the MZR resides $\sim$0.3 dex lower in metallicity than local galaxies and is consistent with the fundamental metallicity relation (FMR) if the low mass slope varies with SFR. At lower redshifts ($z\sim$0.5) our sample reaches $\sim$0.5 dex lower in SFR than current calibrations and we find enhanced metallicities that are consistent with extrapolating the MZR to lower SFRs. Finally, we detect only a $\sim$0.1 dex difference in the metallicities of galaxies in groups versus isolated environments. These results are based on robust calibrations and reach the lowest masses and SFRs that are accessible with HST, providing a critical foundation for studies with the Webb and Roman Space Telescopes. △ Less

Submitted 25 March, 2024; originally announced March 2024.

Comments: Accepted for publication in ApJ on March 23, 2024. The paper has 29 pages, 12 figures, and 6 tables. The calibrated data are available through MAST at: https://archive.stsci.edu/hlsp/mudf

Building the high-redshift Hubble Diagram with quasars

Authors: Matilde Signorini, Guido Risaliti, Andrea Sacchi, Elisabeta Lusso, Emanuele Nardini

Abstract: Proceeding of the "HACK100" Conference, 6-10 June 2022, Trieste, Italy - In recent years, quasars have been shown to be reliable standardizable candles, thanks to the non-linear relation between their X-rays and ultraviolet luminosity. Quasars are also very numerous and they are found at all the observed redshifts: this allows us to investigate the expansion rate of the Universe and the cosmologic… ▽ More Proceeding of the "HACK100" Conference, 6-10 June 2022, Trieste, Italy - In recent years, quasars have been shown to be reliable standardizable candles, thanks to the non-linear relation between their X-rays and ultraviolet luminosity. Quasars are also very numerous and they are found at all the observed redshifts: this allows us to investigate the expansion rate of the Universe and the cosmological parameters in a previously almost untested redshift range ($z\sim2-7$). At redshift higher than 1.5, the Hubble Diagram of quasars shows a significant tension with the predictions of the $Λ$CDM model. I will show how detailed optical/UV and X-rays spectroscopic analysis can be used (i) to obtain more precise distance estimates, and (ii) to derive information about the physical process behind the luminosities relation, and discuss the cosmological implementations. △ Less

Submitted 15 January, 2024; originally announced January 2024.

Comments: Proceeding of the "HACK100" Conference, 6-10 June 2022, Trieste, Italy

Journal ref: Memorie della Società Astronomica Italiana, Vol. 94, n.2, 2023

Quasars as Standard Candles V. Evaluation of a $\leq$ 0.06 dex intrinsic dispersion in the LX-LUV relation

Authors: Matilde Signorini, Guido Risaliti, Elisabeta Lusso, Emanuele Nardini, Giada Bargiacchi, Andrea Sacchi, Bartolomeo Trefoloni

Abstract: A characteristic feature of quasars is the observed non-linear relationship between their monochromatic luminosities at rest-frame 2500 Å and 2 keV. This relationship is evident across all redshifts and luminosities and, due to its non-linearity, can be implemented to estimate quasar distances and construct a Hubble Diagram for quasars. Historically, a significant challenge in the cosmological app… ▽ More A characteristic feature of quasars is the observed non-linear relationship between their monochromatic luminosities at rest-frame 2500 Å and 2 keV. This relationship is evident across all redshifts and luminosities and, due to its non-linearity, can be implemented to estimate quasar distances and construct a Hubble Diagram for quasars. Historically, a significant challenge in the cosmological application of this relation has been its high observed dispersion. Recent studies have demonstrated that this dispersion can be reduced by excluding biased objects from the sample. Nevertheless, the dispersion remains considerable ($δ\sim 0.20$ dex), especially when compared to the Phillips relation for supernovae Ia. Given the absence of a comprehensive physical model for the relation, it remains unclear how much of the remaining dispersion is intrinsically tied to the relation itself and how much can be attributed to observational factors not addressed by the sample selection and by the choice of X-ray and UV indicators. Potential contributing factors include (i) the scatter produced by using X-ray photometric results instead of spectroscopic ones, (ii) the intrinsic variability of quasars, and (iii) the inclination of the accretion disc relative to our line of sight. In this study, we thoroughly examine these three factors and quantify their individual contributions to the observed dispersion. Based on our findings, we argue that the intrinsic dispersion of the X-ray/UV luminosity relation is likely below 0.06 dex. We also discuss why high-redshift subsamples can show a significantly lower dispersion than the average one. △ Less

Submitted 13 December, 2023; originally announced December 2023.

Comments: submitted

Journal ref: A&A 687, A32 (2024)

Euclid preparation. Spectroscopy of active galactic nuclei with NISP

Authors: Euclid Collaboration, E. Lusso, S. Fotopoulou, M. Selwood, V. Allevato, G. Calderone, C. Mancini, M. Mignoli, M. Scodeggio, L. Bisigello, A. Feltre, F. Ricci, F. La Franca, D. Vergani, L. Gabarra, V. Le Brun, E. Maiorano, E. Palazzi, M. Moresco, G. Zamorani, G. Cresci, K. Jahnke, A. Humphrey, H. Landt, F. Mannucci , et al. (224 additional authors not shown)

Abstract: The statistical distribution and evolution of key properties (e.g. accretion rate, mass, or spin) of active galactic nuclei (AGN), remain an open debate in astrophysics. The ESA Euclid space mission, launched on July 1st 2023, promises a breakthrough in this field. We create detailed mock catalogues of AGN spectra, from the rest-frame near-infrared down to the ultraviolet, including emission lines… ▽ More The statistical distribution and evolution of key properties (e.g. accretion rate, mass, or spin) of active galactic nuclei (AGN), remain an open debate in astrophysics. The ESA Euclid space mission, launched on July 1st 2023, promises a breakthrough in this field. We create detailed mock catalogues of AGN spectra, from the rest-frame near-infrared down to the ultraviolet, including emission lines, to simulate what Euclid will observe for both obscured (type 2) and unobscured (type 1) AGN. We concentrate on the red grisms of the NISP instrument, which will be used for the wide-field survey, opening a new window for spectroscopic AGN studies in the near-infrared. We quantify the efficiency in the redshift determination as well as in retrieving the emission line flux of the H$α$+[NII] complex as Euclid is mainly focused on this emission line as it is expected to be the brightest one in the probed redshift range. Spectroscopic redshifts are measured for 83% of the simulated AGN in the interval where the H$α$+[NII] is visible (0.89<z<1.83 at a line flux $>2x10^{-16}$ erg s$^{-1}$ cm$^{-2}$, encompassing the peak of AGN activity at $z\simeq 1-1.5$) within the spectral coverage of the red grism. Outside this redshift range, the measurement efficiency decreases significantly. Overall, a spectroscopic redshift is correctly determined for ~90% of type 2 AGN down to an emission line flux of $3x10^{-16}$ erg s$^{-1}$ cm$^{-2}$, and for type 1 AGN down to $8.5x10^{-16}$ erg s$^{-1}$ cm$^{-2}$. Recovered black hole mass values show a small offset with respect to the input values ~10%, but the agreement is good overall. With such a high spectroscopic coverage at z<2, we will be able to measure AGN demography, scaling relations, and clustering from the epoch of the peak of AGN activity down to the present-day Universe for hundreds of thousand AGN with homogeneous spectroscopic information. △ Less

Submitted 15 January, 2024; v1 submitted 20 November, 2023; originally announced November 2023.

Comments: 29 pages, 23 figures. Submitted to A&A, revised version

Wavelength Dependences of the Optical/UV and X-ray Luminosity Correlations of Quasars

Authors: Chichuan Jin, Elisabeta Lusso, Martin Ward, Chris Done, Riccardo Middei

Abstract: The inter-band correlations between optical/UV and X-ray luminosities of active galactic nuclei (AGN) are important for understanding the disc-coronal connection, as well as using AGN as standard candles for cosmology. It is conventional to measure the X-ray luminosity at rest frame 2 keV and compare to the UV luminosity at the rest-frame 2500 Å, but the wavelength-dependence was never well explor… ▽ More The inter-band correlations between optical/UV and X-ray luminosities of active galactic nuclei (AGN) are important for understanding the disc-coronal connection, as well as using AGN as standard candles for cosmology. It is conventional to measure the X-ray luminosity at rest frame 2 keV and compare to the UV luminosity at the rest-frame 2500 Å, but the wavelength-dependence was never well explored. In this work, we adopt a well-defined sample of 1169 unobscured quasars in the redshift range 0.13 - 4.51, and apply the direct-correlation method to explore how the correlation with the 2 keV luminosity changes at different optical/UV wavelengths, from 1280 - 5550 Å where the spectral quality is high. We find that the luminosity at all UV continuum wavelengths correlates with the X-ray luminosity similarly to that at 2500 Å, and that these correlations are better than at the optical wavelengths. Strong self-correlation is also found in the broadband optical/UV continuum, supporting the scenario that it is dominated by the disc emission. Correlations of various emission lines are also investigated (e.g. C IV, C III], Mg II, H$β$, [O III]$λλ4959/5007$), including the Baldwin effect and correlations involving line-widths. We find the forms of these line correlations are different, and they are also different from their underlying continua, suggesting various complexities in the line-generation process. We discuss these results in the disc-wind scenario. Our study confirms that the rest-frame 2500 Å is a good wavelength to represent the optical/UV continual properties of quasars, and shows the advantages of the direct-correlation method. △ Less

Submitted 26 October, 2023; originally announced October 2023.

Comments: 18 pages, 15 figures, accepted for publication in MNRAS

The MUSE Ultra Deep Field (MUDF). IV. A pair of X-ray weak quasars at the heart of two extended Lyα nebulae

Authors: Elisabeta Lusso, Emanuele Nardini, Michele Fumagalli, Matteo Fossati, Fabrizio Arrigoni Battaia, Mitchell Revalski, Marc Rafelski, Valentina D'Odorico, Celine Peroux, Stefano Cristiani, Pratika Dayal, Francesco Haardt, Emma K. Lofthouse

Abstract: We present the results obtained from follow-up observations of the MUSE Ultra Deep Field (MUDF) at X-ray energies with XMM-Newton. The MUDF is centred on a unique field with two bright, physically associated quasars at $z\simeq3.23$, separated by $\sim$500 kpc in projection. Both quasars are embedded within extended Ly$α$ nebulae ($\gtrsim 100~\rm kpc$ at a surface brightness flux level of… ▽ More We present the results obtained from follow-up observations of the MUSE Ultra Deep Field (MUDF) at X-ray energies with XMM-Newton. The MUDF is centred on a unique field with two bright, physically associated quasars at $z\simeq3.23$, separated by $\sim$500 kpc in projection. Both quasars are embedded within extended Ly$α$ nebulae ($\gtrsim 100~\rm kpc$ at a surface brightness flux level of $\approx 6\times 10^{-19} \rm erg~s^{-1}~cm^{-2}~arcsec^{-2}$), whose elongated morphology is suggestive of an extended filament connecting the quasar haloes. The new X-ray observations presented here allow us to characterise the physical properties (e.g. X-ray slope, luminosities, gas column densities) in the innermost region of the MUDF quasars. We find that both quasars are X-ray underluminous compared to objects at similar ultraviolet luminosities. Based on our X-ray spectral analysis, absorbing columns of $N_H(z)\gtrsim$ 10$^{23}$ cm$^{-2}$ appear unlikely, therefore such a weakness is possibly intrinsic. When also including literature data, we do not observe any detectable trend between the area of the nebulae and nuclear luminosities at both the rest-frame 2 keV and 2500 $\rm \mathring{A}$. The area is also not correlated with the X-ray photon index nor with the integrated band flux in the hard band (2$-$10 keV). We also do not find any trend between the extended Ly$α$ emission of the nebulae and the nuclear X-ray luminosity. Finally, the properties of the MUDF quasars' nebulae are consistent with the observed relation between the Ly$α$ integrated luminosity of the nebulae and their area. Our results suggest that the quasar ionization power is not a strong driver of the morphology and size of the nebulae. △ Less

Submitted 4 September, 2023; v1 submitted 24 August, 2023; originally announced August 2023.

Comments: 15 pages, 9 figures, reference added, published in MNRAS

A re-emerging bright soft-X-ray state of the changing-look Active Galactic Nucleus 1ES~1927+654: a multi-wavelength view

Authors: Ritesh Ghosh, Sibasish Laha, Eileen Meyer, Agniva Roychowdhury, Xiaolong Yang, J. A. Acosta Pulido, Suvendu Rakshit, Shivangi Pandey, Josefa Becerra Gonzalez, Ehud Behar, Luigi C. Gallo, Francesca Panessa, Stefano Bianchi, Fabio La Franca, Nicolas Scepi, Mitchell C. Begelman, Anna Lia Longinotti, Elisabeta Lusso, Samantha Oates, Matt Nicholl, S. Bradley Cenko, Brendan O Connor, Erica Hammerstein, Jincen Jose, Krisztina Eva Gabanyi , et al. (2 additional authors not shown)

Abstract: 1ES1927+654 is a nearby active galactic nucleus that has shown an enigmatic outburst in optical/UV followed by X-rays, exhibiting strange variability patterns at timescales of months-years. Here we report the unusual X-ray, UV, and radio variability of the source in its post-flare state (Jan 2022- May 2023). Firstly, we detect an increase in the soft X-ray (0.3-2 keV) flux from May 2022- May 2023… ▽ More 1ES1927+654 is a nearby active galactic nucleus that has shown an enigmatic outburst in optical/UV followed by X-rays, exhibiting strange variability patterns at timescales of months-years. Here we report the unusual X-ray, UV, and radio variability of the source in its post-flare state (Jan 2022- May 2023). Firstly, we detect an increase in the soft X-ray (0.3-2 keV) flux from May 2022- May 2023 by almost a factor of five, which we call the bright-soft-state. The hard X-ray 2-10 keV flux increased by a factor of two, while the UV flux density did not show any significant changes ($\le 30\%$) in the same period. The integrated energy pumped into the soft and hard X-ray during this period of eleven months is $\sim 3.57\times 10^{50}$ erg and $5.9\times 10^{49}$ erg, respectively. From the energetics, it is evident that whatever is producing the soft excess (SE) is pumping out more energy than either the UV or hard X-ray source. Since the energy source presumably is ultimately the accretion of matter onto the SMBH, the SE emitting region must be receiving the majority of this energy. In addition, the source does not follow the typical disc-corona relation found in AGNs, neither in the initial flare (in 2017-2019) nor in the current bright soft state (2022-2023). We found that the core (<1 pc) radio emission at 5 GHz gradually increased till March 2022 but showed a dip in August 2022. The Güdel Benz relation ($L_{\rm radio}/L_{\rm X-ray}\sim 10^{-5}$), however, is still within the expected range for radio-quiet AGN and further follow-up radio observations are currently being undertaken. △ Less

Submitted 11 August, 2023; v1 submitted 7 August, 2023; originally announced August 2023.

Comments: Accepted for publication in ApJ

Quasars as Standard Candles IV. Analysis of the X-ray and UV indicators of the disc-corona relation

Authors: Matilde Signorini, Guido Risaliti, Elisabeta Lusso, Emanuele Nardini, Giada Bargiacchi, Andrea Sacchi, Bartolomeo Trefoloni

Abstract: Context: A non-linear relation between quasar monochromatic luminosities at 2500A and 2 keV holds at all observed redshifts and luminosities, and it has been used to derive quasar distances and to build a Hubble Diagram of quasars. The choice of the X-ray and UV indicators has so far been somewhat arbitrary, and has typically relied on photometric data. Aims: We want to determine the X-ray and UV… ▽ More Context: A non-linear relation between quasar monochromatic luminosities at 2500A and 2 keV holds at all observed redshifts and luminosities, and it has been used to derive quasar distances and to build a Hubble Diagram of quasars. The choice of the X-ray and UV indicators has so far been somewhat arbitrary, and has typically relied on photometric data. Aims: We want to determine the X-ray and UV proxies that provide the smallest dispersion of the relation, in order to obtain more precise distance estimates, and to confirm the reliability of the X-ray to UV relation as a distance indicator. Methods: We performed a complete UV spectroscopic analysis of a sample of $\sim$1800 quasars with SDSS optical spectra and XMM- Newton X-ray serendipitous observations. In the X-rays, we analysed the spectra of all the sample objects at redshift z $>$1.9, while we relied on photometric measurements at lower redshifts. As done in previous studies, we analysed the relation in small redshift bins, using fluxes instead of luminosities. Results: We show that the monochromatic fluxes at 1 keV and 2500A are, respectively, the best X-ray and UV continuum indicators among those that are typically available. We also find a tight relation between soft X-ray and Mg ii2800A line fluxes, and a marginal dependence of the X-ray to UV relation on the width of the Mg ii line. Conclusions: Our analysis suggests that the physical quantities that are more tightly linked to one another are the soft X-ray flux at $\sim$1 keV and the ionizing UV flux blueward of the Lyman limit. However, the "usual" monochromatic fluxes at 2 keV and 2500A estimated from photometric data provide an almost as-tight X-ray to UV relation, and can be used to derive quasar distances. The Hubble diagram obtained using spectroscopic indicators is fully consistent with the one presented in previous papers, based on photometric data. △ Less

Submitted 28 June, 2023; originally announced June 2023.

Comments: accepted for publication in A&A

Journal ref: A&A 676, A143 (2023)

MUSE adaptive-optics spectroscopy confirms dual active galactic nuclei and strongly lensed systems at sub-arcsec separation

Authors: M. Scialpi, F. Mannucci, C. Marconcini, G. Venturi, E. Pancino, A. Marconi, G. Cresci, F. Belfiore, A. Amiri, E. Bertola, S. Carniani, C. Cicone, A. Ciurlo, Q. D'Amato, M. Ginolfi, E. Lusso, A. Marasco, E. Nardini, K. Rubinur, P. Severgnini, G. Tozzi, L. Ulivi, C. Vignali, M. Volonteri

Abstract: The novel Gaia Multi Peak (GMP) technique has proven to be able to successfully select dual and lensed AGN candidates at sub-arcsec separations. Both populations are important because dual AGN represent one of the central, still largely untested, predictions of lamdaCDM cosmology, and compact lensed quasars allow to probe the central regions of the lensing galaxies. In this work, we present high s… ▽ More The novel Gaia Multi Peak (GMP) technique has proven to be able to successfully select dual and lensed AGN candidates at sub-arcsec separations. Both populations are important because dual AGN represent one of the central, still largely untested, predictions of lamdaCDM cosmology, and compact lensed quasars allow to probe the central regions of the lensing galaxies. In this work, we present high spatial resolution spectroscopy of twelve GMP-selected systems. We use the the adaptive-optics assisted integral-field spectrograph MUSE at VLT to resolve each system and study the nature of each component. All the targets reveal the presence of two components confirming the GMP selection. We classify five targets as dual AGN, two as lensed systems, and five as a chance alignment of a star and and AGN. Having separations between 0.30" and 0.86", these dual and lensed systems are, to date, among the most compact ever discovered at z >0.3. This is the largest sample of distant dual AGN with sub-arcsec separations ever presented in a single paper. △ Less

Submitted 16 July, 2024; v1 submitted 19 May, 2023; originally announced May 2023.

Comments: 16 pages, 11 figures

Journal ref: A&A 690, A57 (2024)

On the Metallicities and Kinematics of the Circumgalactic Media of Damped Ly$α$ Systems at $z \sim 2.5$

Authors: Stephanie M. Urbano Stawinski, Kate H. R. Rubin, J. Xavier Prochaska, Joseph F. Hennawi, Nicolas Tejos, Michele Fumagalli, Marc Rafelski, Evan N. Kirby, Elisabeta Lusso, Zachary Hafen

Abstract: We use medium- and high-resolution spectroscopy of close pairs of quasars to analyze the circumgalactic medium (CGM) surrounding 32 damped Ly$α$ absorption systems (DLAs). The primary quasar sightline in each pair probes an intervening DLA in the redshift range $1.6<z_\text{abs}<3.5$, such that the secondary sightline probes absorption from Ly$α$ and a large suite of metal-line transitions (includ… ▽ More We use medium- and high-resolution spectroscopy of close pairs of quasars to analyze the circumgalactic medium (CGM) surrounding 32 damped Ly$α$ absorption systems (DLAs). The primary quasar sightline in each pair probes an intervening DLA in the redshift range $1.6<z_\text{abs}<3.5$, such that the secondary sightline probes absorption from Ly$α$ and a large suite of metal-line transitions (including $~\rm OI$, $~\rm CII$, $~\rm CIV$, $~\rm SiII$, and $~\rm SiIV$) in the DLA host galaxy's CGM at transverse distances $24\ \text{kpc}\le R_\bot\le284~\rm kpc$. Analysis of Ly$α$ in the CGM sightlines shows an anti-correlation between $R_\bot$ and $~\rm HI$ column density ($N_\text{HI}$) with 99.8$\%$ confidence, similar to that observed around luminous galaxies. The incidences of $~\rm CII$ and $~\rm SiII$ with $N>10^{13}~\rm cm^{-2}$ within 100 kpc of DLAs are larger by $2σ$ than those measured in the CGM of Lyman break galaxies (C$_f(N_\text{CII})>0.89$ and C$_f(N_\text{SiII})=0.75_{-0.17}^{+0.12}$). Metallicity constraints derived from ionic ratios for nine CGM systems with negligible ionization corrections and $N_\text{HI}>10^{18.5}~\rm cm^{-2}$ show a significant degree of scatter (with metallicities/limits across the range $-2.06\lesssim\log Z/Z_{\odot}\lesssim-0.75$), suggesting inhomogeneity in the metal distribution in these environments. Velocity widths of $\text{CIV}\lambda1548$ and low-ionization metal species in the DLA vs. CGM sightlines are strongly ($>2σ$) correlated, suggesting they trace the potential well of the host halo over $R_\bot\lesssim300$ kpc scales. At the same time, velocity centroids for $\text{CIV}\lambda1548$ differ in DLA vs. CGM sightlines by $>100~\rm km\ s^{-1}$ for $\sim50\%$ of velocity components, but few components have velocities that would exceed the escape velocity assuming dark matter host halos of $\ge10^{12}M_\odot$. △ Less

Submitted 18 May, 2023; originally announced May 2023.

Comments: 44 pages, 21 Figures, 5 Tables, accepted for publication in ApJ

The most luminous blue quasars at 3.0<z<3.3 -- III. LBT spectra and accretion parameters

Authors: Bartolomeo Trefoloni, Elisabeta Lusso, Emanuele Nardini, Guido Risaliti, Giada Bargiacchi, Susanna Bisogni, Francesca M. Civano, Martin Elvis, Giuseppina Fabbiano, Roberto Gilli, Alessandro Marconi, Gordon T. Richards, Andrea Sacchi, Francesco Salvestrini, Matilde Signorini, Cristian Vignali

Abstract: We present the analysis of the rest frame ultraviolet and optical spectra of 30 bright blue quasars at $z\sim3$, selected to examine the suitability of AGN as cosmological probes. In our previous works, we found an unexpectedly high fraction ($\approx 25 \%$) of X-ray weak quasars in the sample. The latter sources also display a flatter UV continuum and a broader and fainter CIV profile in the arc… ▽ More We present the analysis of the rest frame ultraviolet and optical spectra of 30 bright blue quasars at $z\sim3$, selected to examine the suitability of AGN as cosmological probes. In our previous works, we found an unexpectedly high fraction ($\approx 25 \%$) of X-ray weak quasars in the sample. The latter sources also display a flatter UV continuum and a broader and fainter CIV profile in the archival UV data with respect to their X-ray normal counterparts. Here we present new observations with the LBT in both the $zJ$ (rest-frame $\simeq$2300-3100 $\rm \mathring{A}$) and the $K_S$ ($\simeq$4750-5350 $\rm \mathring{A}$) bands. We estimated black hole masses ($M_{\rm BH}$) and Eddington ratios ($λ_{\rm Edd}$) from the from the H$β$ and MgII emission lines, finding that our $z\sim3$ quasars are on average highly accreting ($\langle λ_{\rm Edd} \rangle\simeq 1.2$ and $\langle M_{\rm BH} \rangle\simeq 10^{9.7}M_\odot$), with no difference in $λ_{\rm Edd}$ or $M_{\rm BH}$ between X-ray weak and X-ray normal quasars. From the $zJ$ spectra, we derive flux and equivalent width of MgII and FeII, finding that X-ray weak quasars display higher FeII/MgII ratios with respect to typical quasars. FeII/MgII ratios of X-ray normal quasars are instead consistent with other estimates up to $z\simeq6.5$, corroborating the idea of already chemically mature BLRs at early cosmic time. From the $K_S$ spectra, we find that all the X-ray weak quasars present generally weaker [OIII] emission (EW<10 $\rm \mathring{A}$) than the normal ones. The sample as a whole, however, abides by the known X-ray/[OIII] luminosity correlation, hence the different [OIII] properties are likely due to an intrinsically weaker [OIII] emission in X-ray weak objects, associated to the shape of the spectral energy distribution. We interpret these results in the framework of accretion-disc winds. △ Less

Submitted 12 May, 2023; originally announced May 2023.

Comments: 25 pages, 17 figures, Accepted for publication on Astronomy & Astrophysics

Quasars as high-redshift standard candles

Authors: Guido Risaliti, Elisabeta Lusso, Emanuele Nardini, Giada Bargiacchi, Susanna Bisogni, Andrea Sacchi, Matilde Signorini, Bartolomeo Trefoloni

Abstract: In the past few years, we built a Hubble diagram of quasars up to redshift z$\sim$7, based on the nonlinear relation between quasars' x-ray and UV luminosities. Such a Hubble diagram shows a >4$σ$ deviation from the standard flat $Λ$CDM model at z>1.5. Given the important consequences of this result, it is fundamental to rule out any systematic effect in the selection of the sample and/or in the f… ▽ More In the past few years, we built a Hubble diagram of quasars up to redshift z$\sim$7, based on the nonlinear relation between quasars' x-ray and UV luminosities. Such a Hubble diagram shows a >4$σ$ deviation from the standard flat $Λ$CDM model at z>1.5. Given the important consequences of this result, it is fundamental to rule out any systematic effect in the selection of the sample and/or in the flux measurements, and to investigate possible redshift dependences of the relation, that would invalidate the use of quasars as standard candles. Here we review all the observational results supporting our method: the match of the Hubble diagram of quasars with that of supernovae in the common redshift range, the constant slope of the relation at all redshifts, the redshift non-evolution of the spectral properties of our sources both in the x-rays and in the UV. An independent test of our results requires the observation of other standard candles at high redshift. In particular, we expect that future observations of supernovas at z>2 will confirm the deviation from the concordance model found with the Hubble diagram of quasars. △ Less

Submitted 26 April, 2023; originally announced April 2023.

Journal ref: published in Astronomische Nachrichten, 2023

The MUSE Ultra Deep Field (MUDF). III. Hubble Space Telescope WFC3 Grism Spectroscopy and Imaging

Authors: Mitchell Revalski, Marc Rafelski, Michele Fumagalli, Matteo Fossati, Norbert Pirzkal, Ben Sunnquist, Laura J. Prichard, Alaina Henry, Micaela Bagley, Rajeshwari Dutta, Giulia Papini, Fabrizio Arrigoni Battaia, Valentina D'Odorico, Pratika Dayal, Vicente Estrada-Carpenter, Emma K. Lofthouse, Elisabeta Lusso, Simon L. Morris, Kalina V. Nedkova, Casey Papovich, Celine Peroux

Abstract: We present extremely deep Hubble Space Telescope (HST) Wide Field Camera 3 (WFC3) observations of the MUSE Ultra Deep Field (MUDF). This unique region of the sky contains two quasars at $z \approx$ 3.22 that are separated by only $\sim$500 kpc, providing a stereoscopic view of gas and galaxies in emission and absorption across $\sim$10 billion years of cosmic time. We have obtained 90 orbits of HS… ▽ More We present extremely deep Hubble Space Telescope (HST) Wide Field Camera 3 (WFC3) observations of the MUSE Ultra Deep Field (MUDF). This unique region of the sky contains two quasars at $z \approx$ 3.22 that are separated by only $\sim$500 kpc, providing a stereoscopic view of gas and galaxies in emission and absorption across $\sim$10 billion years of cosmic time. We have obtained 90 orbits of HST WFC3 G141 near-infrared grism spectroscopy of this field in a single pointing, as well as 142 hours of optical spectroscopy with the Very Large Telescope (VLT) Multi Unit Spectroscopic Explorer (MUSE). The WFC3 (F140W, F125W, and F336W) and archival WFPC2 (F702W and F450W) imaging provides five-filter photometry that we use to detect 3,375 sources between $z \approx$ 0 - 6, including 1,536 objects in a deep central pointing with both spectroscopic and photometric coverage. The F140W and F336W mosaics reach exceptional depths of $m_\mathrm{AB}\approx$ 28 and 29, respectively, providing near-infrared and rest-frame ultraviolet information for 1,580 sources, and we reach 5$σ$ continuum detections for objects as faint as $m_\mathrm{AB}\approx$ 27 in the grism spectra. The extensive wavelength coverage of MUSE and WFC3 allows us to measure spectroscopic redshifts for 419 sources, down to galaxy stellar masses of log(M/M$_{\odot}$) $\approx$ 7 at $z \approx$ 1 - 2. In this publication, we provide the calibrated HST data and source catalogs as High Level Science Products for use by the community, which includes photometry, morphology, and redshift measurements that enable a variety of studies aimed at advancing our models of galaxy formation and evolution in different environments. △ Less

Submitted 16 March, 2023; v1 submitted 2 February, 2023; originally announced February 2023.

Comments: Accepted for publication in ApJS on February 1, 2023. The paper has 25 pages, 13 figures, and 7 tables. Version two includes minor corrections to match the journal publication. The calibrated data are available through MAST at: https://archive.stsci.edu/hlsp/mudf

The SOUX AGN Sample: SDSS-XMM-Newton Optical, Ultraviolet and X-ray selected active galactic nuclei spanning a wide range of parameter space -- Sample definition

Authors: Daniel Kynoch, Jake A. J. Mitchell, Martin J. Ward, Chris Done, Elisabeta Lusso, Hermine Landt

Abstract: We assemble a sample of 696 type 1 AGN up to a redshift of $z=2.5$, all of which have an SDSS spectrum containing at least one broad emission line (H $α$, H $β$ or Mg II) and an XMM-Newton X-ray spectrum containing at least 250 counts in addition to simultaneous optical/ultraviolet photometry from the XMM Optical Monitor. Our sample includes quasars and narrow-line Seyfert 1s: thus our AGN span a… ▽ More We assemble a sample of 696 type 1 AGN up to a redshift of $z=2.5$, all of which have an SDSS spectrum containing at least one broad emission line (H $α$, H $β$ or Mg II) and an XMM-Newton X-ray spectrum containing at least 250 counts in addition to simultaneous optical/ultraviolet photometry from the XMM Optical Monitor. Our sample includes quasars and narrow-line Seyfert 1s: thus our AGN span a wide range in luminosity, black hole mass and accretion rate. We determine single-epoch black hole mass relations for the three emission lines and find that they provide broadly consistent mass estimates whether the continuum or emission line luminosity is used as the proxy for the broad emission line region radius. We explore variations of the UV/X-ray energy index $α_\mathrm{ox}$ with the UV continuum luminosity and with black hole mass and accretion rate, and make comparisons to the physical quasar spectral energy distribution (SED) model QSOSED. The majority of the AGN in our sample lie in a region of parameter space with $0.02<L/L_\mathrm{Edd}<2$ as defined by this model, with narrow-line type 1 AGN offset to lower masses and higher accretion rates than typical broad-line quasars. We find differences in the dependence of $α_\mathrm{ox}$ on UV luminosity between both narrow/broad-line and radio-loud/quiet subsets of AGN: $α_\mathrm{ox}$ has a slightly weaker dependence on UV luminosity for broad-line AGN and radio-loud AGN have systematically harder $α_\mathrm{ox}$. △ Less

Submitted 18 January, 2023; originally announced January 2023.

Comments: 23 pages, 24 figures and 10 tables. Accepted for publication in MNRAS

New multiple AGN systems with sub-arcsec separation: confirmation of candidates selected via the novel GMP method

Authors: A. Ciurlo, F. Mannucci, S. Yeh, A. Amiri, S. Carniani, C. Cicone, G. Cresci, R. Khatun, E. Lusso, A. Marasco, C. Marconcini, A. Marconi, E. Nardini, E. Pancino, P. Rosati, P. Severgnini, M. Scialpi, G. Tozzi, G. Venturi, C. Vignali, M. Volonteri

Abstract: The existence of multiple active galactic nuclei (AGN) at small projected distances on the sky is due to either the presence of multiple, in-spiraling SMBHs, or to gravitational lensing of a single AGN. Both phenomena allow us to address important astrophysical and cosmological questions. However, few kpc-separation multiple AGN are currently known. Recently, the newly-developed Gaia Multi peak (G… ▽ More The existence of multiple active galactic nuclei (AGN) at small projected distances on the sky is due to either the presence of multiple, in-spiraling SMBHs, or to gravitational lensing of a single AGN. Both phenomena allow us to address important astrophysical and cosmological questions. However, few kpc-separation multiple AGN are currently known. Recently, the newly-developed Gaia Multi peak (GMP) method provided numerous new candidate members of these populations. We present spatially resolved, integral-field spectroscopy of a sample of four GMP-selected multiple AGNs candidates. In all of these systems, we detect two or more components with sub-arcsec separations. We find that two of the systems are dual AGNs, one is either an intrinsic triple or a lensed dual AGN, while the last system is a chance AGN/star alignment. Our observations double the number of confirmed multiple AGNs at projected separations below 7 kpc at z > 0.5, present the first detection of a possible triple AGN in a single galaxy at z > 0.5, and successfully test the GMP method as a novel technique to discover previously unknown multiple AGNs. △ Less

Submitted 8 January, 2023; originally announced January 2023.

Comments: 6 pages, 2 figures

Journal ref: A&A 671, L4 (2023)

The WISSH quasars project XI. The mean Spectral Energy Distribution and Bolometric Corrections of the most luminous quasars

Authors: Ivano Saccheo, Angela Bongiorno, Enrico Piconcelli, Manuela Bischetti, Gabriele Bruni, Giovanni Cresci, Chiara Feruglio, Fabrizio Fiore, Andrea Grazian, Alfredo Luminari, Elisabeta Lusso, Vincenzo Mainieri, Roberto Maiolino, Alessandro Marconi, Federica Ricci, Francesco Tombesi, Andrea Travascio, Giustina Vietri, Cristian Vignali, Luca Zappacosta, Fabio La Franca

Abstract: Hyper-luminous Quasi-Stellar Objects (QSOs) represent the ideal laboratory to investigate Active Galactic Nuclei (AGN) feedback mechanism since their formidable energy release causes powerful winds at all scales and thus the maximum feedback is expected. We aim at deriving the mean Spectral Energy Distribution (SED) of a sample of 85 WISE-SDSS Selected Hyper-luminous (WISSH) quasars. Since the S… ▽ More Hyper-luminous Quasi-Stellar Objects (QSOs) represent the ideal laboratory to investigate Active Galactic Nuclei (AGN) feedback mechanism since their formidable energy release causes powerful winds at all scales and thus the maximum feedback is expected. We aim at deriving the mean Spectral Energy Distribution (SED) of a sample of 85 WISE-SDSS Selected Hyper-luminous (WISSH) quasars. Since the SED provides a direct way to investigate the AGN structure, our goal is to understand if quasars at the bright end of the luminosity function have peculiar properties compared to the bulk of the population. We built a mean intrinsic SED after correcting for the dust extinction, absorption and emission lines and intergalactic medium absorption. We also derived bolometric, IR band and monochromatic luminosities together with bolometric corrections at lambda = 5100 A and 3 micron. We define a new relation for the 3 micron bolometric correction. We find that the mean SED of hyper-luminous WISSH QSOs is different from that of less luminous sources, i.e. a relatively lower X-ray emission and a near and mid IR excess which can be explained assuming a larger dust contribution. WISSH QSOs have stronger emission from both warm and very hot dust, the latter being responsible for shifting the typical dip of the AGN SED from 1.3 to 1.1 micron. We also derived the mean SEDs of two sub-samples created according to the presence of Broad Absorption Lines and equivalent width of CIV line. We confirm that BALs are X-ray weak and that they have a reddened UV-optical continuum. We also find that BALs tend to have stronger emission from the hot dust component. This analysis suggests that hyper-luminous QSOs have a peculiar SED compared to less luminous objects. It is therefore critical to use SED templates constructed exclusively from very bright quasars samples when dealing with particularly luminous sources. △ Less

Submitted 14 November, 2022; originally announced November 2022.

Comments: Accepted for publication in A&A. 20 pages, 15 figures

Hands-on learning at a world-class telescope

Authors: Elisabeta Lusso, Lapo Casetti, Maurizio Pancrazzi, Marco Romoli

Abstract: For the first time, an Italian University has the possibility to perform a multi-year observing campaign at a world-class telescope. This hands-on experience had a significant impact on the students' university path: from learning specific observing techniques on-site to teamwork and collaboration. In this paper we present the results of an observing campaign carried out at the Telescopio Nazional… ▽ More For the first time, an Italian University has the possibility to perform a multi-year observing campaign at a world-class telescope. This hands-on experience had a significant impact on the students' university path: from learning specific observing techniques on-site to teamwork and collaboration. In this paper we present the results of an observing campaign carried out at the Telescopio Nazionale Galileo (TNG) located in La Palma (Canary Islands, Spain) by undergraduate students of the Department of Physics and Astronomy, at the University of Firenze. △ Less

Submitted 24 October, 2022; originally announced October 2022.

Comments: 8 pages, 3 figures, proceedings of the 8th International Conference on Higher Education Advances (HEAd'22)

The SOUX AGN sample: Optical/UV/X-ray SEDs and the nature of the disc

Authors: Jake A. J. Mitchell, Chris Done, Martin J. Ward, Daniel Kynoch, Scott Hagen, Elisabeta Lusso, Hermine Landt

Abstract: We use the SOUX sample of $\sim$700 AGN to form average optical-UV-X-rays SEDs on a 2D grid of $M_{\mathrm{BH}}$ and $L_{2500}$. We compare these with the predictions of a new AGN SED model, QSOSED, which includes prescriptions for both hot and warm Comptonisation regions as well as an outer standard disc. This predicts the overall SED fairly well for 7.5<log($M_{\mathrm{BH}}/M_{\mathrm{\odot}}$)<… ▽ More We use the SOUX sample of $\sim$700 AGN to form average optical-UV-X-rays SEDs on a 2D grid of $M_{\mathrm{BH}}$ and $L_{2500}$. We compare these with the predictions of a new AGN SED model, QSOSED, which includes prescriptions for both hot and warm Comptonisation regions as well as an outer standard disc. This predicts the overall SED fairly well for 7.5<log($M_{\mathrm{BH}}/M_{\mathrm{\odot}}$)<9.0 over a wide range in $L/L_{\mathrm{Edd}}$, but at higher masses the outer disc spectra in the model are far too cool to match the data. We create optical-UV composites from the entire SDSS sample and use these to show that the mismatch is due to there being no significant change in spectral shape of the optical-UV continuum across several decades of $M_{\mathrm{BH}}$ at constant luminosity. We show for the first time that this cannot be matched by standard disc models with high black hole spin. These apparently fit, but are not self-consistent as they do not include the General Relativistic effects for the emission to reach the observer. At high spin, increased gravitational redshift compensates for almost all of the higher temperature emission from the smaller inner disc radii. The data do not match the predictions made by any current accretion flow model. Either the disc is completely covered by a warm Comptonisation layer whose properties change systematically with $L/L_{\mathrm{Edd}}$, or the accretion flow structure is fundamentally different to that of the standard disc models. △ Less

Submitted 9 June, 2023; v1 submitted 21 October, 2022; originally announced October 2022.

Comments: Accepted 2023 June 5 by MNRAS

The optically elusive, changing-look active nucleus in NGC 4156

Authors: Giulia Tozzi, Elisabeta Lusso, Lapo Casetti, Marco Romoli, Gloria Andreuzzi, Isabel Montoya A., Emanuele Nardini, Giovanni Cresci, Riccardo Middei, Silvia Bertolini, Paolo Calabretto, Vieri Cammelli, Francisco Cuadra, Marco Dalla Ragione, Cosimo Marconcini, Adriano Miceli, Irene Mini, Martina Palazzini, Giorgio Rotellini, Andrea Saccardi, Lavinia Samà, Mattia Sangalli, Lorenzo Serafini, Fabio Spaccino

Abstract: We report on the changing-look nature of the active galactic nucleus (AGN) in the galaxy NGC 4156, as serendipitously discovered thanks to data acquired in 2019 at the Telescopio Nazionale Galileo (TNG) during a students' observing programme. Previous optical spectra had never shown any signatures of broad-line emission, and evidence of the AGN had come only from X-ray observations, being the opti… ▽ More We report on the changing-look nature of the active galactic nucleus (AGN) in the galaxy NGC 4156, as serendipitously discovered thanks to data acquired in 2019 at the Telescopio Nazionale Galileo (TNG) during a students' observing programme. Previous optical spectra had never shown any signatures of broad-line emission, and evidence of the AGN had come only from X-ray observations, being the optical narrow-line flux ratios unable to unambiguously denote this galaxy as a Seyfert. Our 2019 TNG data unexpectedly revealed the appearance of broad-line components in both the H$α$ and H$β$ profiles, along with a rise of the continuum, thus implying a changing-look AGN transitioning from a type 2 (no broad-line emission) towards a (nearly) type 1. The broad-line emission has then been confirmed by our 2022 follow-up observations, whereas the rising continuum has no longer been detected, which hints at a further evolution backwards to a (nearly) type 2. The presence of broad-line components also allowed us to obtain the first single-epoch estimate of the black hole mass (log(MBH/Msun) $\sim$ 8.1) in this source. The observed spectral variability might be the result of a change in the accretion activity of NGC 4156, although variable absorption cannot be completely excluded. △ Less

Submitted 17 October, 2022; originally announced October 2022.

Comments: 9 pages, 6 figures. Accepted for publication in A&A Letters

Journal ref: A&A 667, L12 (2022)

Quasars as high-redshift standard candles

Authors: A. Sacchi, G. Risaliti, M. Signorini, E. Lusso, E. Nardini, G. Bargiacchi, S. Bisogni, F. Civano, M. Elvis, G. Fabbiano, R. Gilli, B. Trefoloni, C. Vignali

Abstract: The non-linear relation between the X-ray and ultraviolet (UV) luminosity in quasars has been used to derive quasar distances and to build a Hubble diagram at redshifts up to $z\sim$ 7. This cosmological application is based on the assumption of independence of the relation on redshift and luminosity. We want to test the reliability of this hypothesis by studying the spectroscopic properties of hi… ▽ More The non-linear relation between the X-ray and ultraviolet (UV) luminosity in quasars has been used to derive quasar distances and to build a Hubble diagram at redshifts up to $z\sim$ 7. This cosmological application is based on the assumption of independence of the relation on redshift and luminosity. We want to test the reliability of this hypothesis by studying the spectroscopic properties of high-redshift quasars in the X-ray and UV bands. We performed a one-by-one analysis of a sample of 130 quasars at $z>$ 2.5 with high-quality X-ray and UV spectroscopic observations. We found that not only the X-ray to UV correlation still holds at these redshifts, but its intrinsic dispersion is as low as 0.12 dex (previous works reached 0.20$-$0.22 dex). For a sample of quasars at $z\sim$ 3 with particularly high-quality observations the dispersion further drops to 0.09 dex, a value entirely accountable for by intrinsic variability and source geometry effects. The composite spectra of these quasars, in both the X-rays and the UV, do not show any difference with respect to the average spectra of quasars at lower redshifts. The absence of any spectral difference between high- and low-$z$ quasars and the tightness of the X-ray to UV relation suggests that no evolutionary effects are present in the relation. Therefore, it can be safely employed to derive quasar distances. Under this assumption, we obtain a measurement of the luminosity distance at $z\sim$ 3 with 15 % uncertainty, and in a 4$σ$ tension with the concordance model. △ Less

Submitted 27 June, 2022; originally announced June 2022.

Comments: Accepted for publication in Astronomy & Astrophysics Letters, 8 pages, 6 figures

Journal ref: A&A 663, L7 (2022)

Constraining the Size of the Circumgalactic Medium Using the Transverse Autocorrelation Function of C IV Absorbers in Paired Quasar Spectra

Authors: Abby Mintz, Marc Rafelski, Regina A. Jorgenson, Michele Fumagalli, Rajeshwari Dutta, Crystal L. Martin, Elisabeta Lusso, Kate H. R. Rubin, John M. O'Meara

Abstract: The circumgalactic medium (CGM) plays a vital role in the formation and evolution of galaxies, acting as a lifeline between galaxies and the surrounding intergalactic medium (IGM). In this study we leverage a unique sample of quasar pairs to investigate the properties of the CGM with absorption line tomography. We present a new sample of medium resolution Keck/ESI, Magellan/MagE, and VLT/XSHOOTER… ▽ More The circumgalactic medium (CGM) plays a vital role in the formation and evolution of galaxies, acting as a lifeline between galaxies and the surrounding intergalactic medium (IGM). In this study we leverage a unique sample of quasar pairs to investigate the properties of the CGM with absorption line tomography. We present a new sample of medium resolution Keck/ESI, Magellan/MagE, and VLT/XSHOOTER spectra of 29 quasar pairs at redshift $2 < z < 3$. We supplement the sample with additional spectra of 32 pairs from the literature, creating a catalog of 61 quasar pairs with angular separations between 1.7" and 132.9" and projected physical separations ($r_\perp$) between 14 kpc and 887 kpc. We construct a catalog of 906 metal-line absorption doublets of C IV ($λλ1548, 1550$) with equivalent widths ranging from 6 mÅ $\leq W_{r, 1550} \leq 2053$ mÅ. The best fit linear model to the log-space equivalent width frequency distribution ($\log f(W_r) = m\log(W_{r}) + b$) of the sample yields coefficients of $m=-1.44\pm0.16$ and $b=-0.43\pm0.16$. To constrain the projected extent of C IV, we calculate the transverse autocorrelation function. The flattening of the autocorrelation function at low $r_\perp$ provides a lower limit for the coherence length of the metal enriched CGM - on the order of 200 $h^{-1}$ comoving kpc. This physical size constraint allows us to refine our understanding of the metals in the CGM, where the extent of C IV in the CGM depends on gas flows, feedback, timescale of metal injection and mixing, and the mass of the host galaxies. △ Less

Submitted 7 June, 2022; originally announced June 2022.

Comments: 19 pages, 8 figures, 2 tables, Accepted for publication by The Astronomical Journal

The Dawn of Black Holes

Authors: Elisabeta Lusso, Rosa Valiante, Fabio Vito

Abstract: In the last decades, luminous accreting super-massive black holes have been discovered within the first Gyr after the Big Bang, but their origin is still an unsolved mystery. We discuss our state-of-the-art theoretical knowledge of their formation physics and early growth, and describe the results of dedicated observational campaigns in the X-ray band. We also provide an overview of how these syst… ▽ More In the last decades, luminous accreting super-massive black holes have been discovered within the first Gyr after the Big Bang, but their origin is still an unsolved mystery. We discuss our state-of-the-art theoretical knowledge of their formation physics and early growth, and describe the results of dedicated observational campaigns in the X-ray band. We also provide an overview of how these systems can be used to derive cosmological parameters. Finally, we point out some open issues, in light of future electro-magnetic and gravitational-wave astronomical facilities. △ Less

Submitted 30 May, 2022; originally announced May 2022.

Comments: This Chapter will appear in the Section "Active Galactic Nuclei in X and Gamma-rays" (Section Editors: A. de Rosa, C. Vignali) of the "Handbook of X-ray and Gamma-ray Astrophysics" (Editors in chief: C. Bambi and A. Santangelo)

Unveiling the population of dual- and lensed- AGNs at sub-arcsec separations

Authors: Filippo Mannucci, Elena Pancino, Francesco Belfiore, Claudia Cicone, Anna Ciurlo, Giovanni Cresci, Elisabeta Lusso, Antonino Marasco, Alessandro Marconi, Emanuele Nardini, Enrico Pinna, Paola Severgnini, Paolo Saracco, Giulia Tozzi, Sherry Yeh

Abstract: All cosmological models of structure formation predict the existence of a widespread population of dual supermassive black holes in-spiralling inside their common host galaxy, eventually merging and giving rise to intense gravitational waves. These systems can be identified as dual AGNs at kilo parsec separations, but only very few have been confirmed at z>0.5. The appearance of multiple AGNs at s… ▽ More All cosmological models of structure formation predict the existence of a widespread population of dual supermassive black holes in-spiralling inside their common host galaxy, eventually merging and giving rise to intense gravitational waves. These systems can be identified as dual AGNs at kilo parsec separations, but only very few have been confirmed at z>0.5. The appearance of multiple AGNs at small angular separations can also be due to gravitational lensing of single AGNs, which are themselves very important systems for many astrophysical topics. Here we present a novel technique, dubbed the Gaia Multipeak (GMP) method, to obtain large and reliable samples of dual/lensed AGN candidates with sub-arcsec separations by looking for AGNs showing multiple peaks in the light profiles observed by the Gaia satellite. All the GMP-selected sources with high resolution images (26 from the HST archive and 5 from dedicated adaptive-optics assisted imaging at the Large Binocular Telescope) show multiple components with sub-arcsec separation pointing toward a very high reliability of the method. By sampling separations down to ~2 kpc at z>1, this method allows us to probe the physical processes that drive the inspiralling of a pair of SMBHs inside a single galaxy. △ Less

Submitted 10 October, 2022; v1 submitted 21 March, 2022; originally announced March 2022.

Comments: Nature Astronomy (2022)

A radio, optical, UV and X-ray view of the enigmatic changing look Active Galactic Nucleus 1ES~1927+654 from its pre- to post-flare states

Authors: Sibasish Laha, Eileen Meyer, Agniva Roychowdhury, Josefa Becerra González, J. A. Acosta-Pulido, Aditya Thapa, Ritesh Ghosh, Ehud Behar, Luigi C. Gallo, Gerard A. Kriss, Francesca Panessa, Stefano Bianchi, Fabio La Franca, Nicolas Scepi, Mitchell C. Begelman, Anna Lia Longinotti, Elisabeta Lusso, Samantha Oates, Matt Nicholl, S. Bradley Cenko

Abstract: The nearby type-II AGN 1ES1927+654 went through a violent changing-look (CL) event beginning December 2017 during which the optical and UV fluxes increased by four magnitudes over a few months, and broad emission lines newly appeared in the optical/UV. By July 2018 the X-ray coronal emission had completely vanished, only to reappear a few months later. In this work we report the evolution of the r… ▽ More The nearby type-II AGN 1ES1927+654 went through a violent changing-look (CL) event beginning December 2017 during which the optical and UV fluxes increased by four magnitudes over a few months, and broad emission lines newly appeared in the optical/UV. By July 2018 the X-ray coronal emission had completely vanished, only to reappear a few months later. In this work we report the evolution of the radio, optical, UV and X-rays from the pre-flare state through mid-2021 with new and archival data from the Very Long Baseline Array (VLBA), the European VLBI Network, the Very Large Array (VLA), the Telescopio Nazionale Galileo (TNG), Gran Telescopio Canarias (GTC), The Neil Gehrels Swift observatory and XMM-Newton. The main results from our work are: (1) The source has returned to its pre-CL state in optical, UV, and X-ray; the disk-corona relation has been re-established as has been in the pre-CL state, with an $α_{\rm OX}\sim 1.02$. The optical spectra are dominated by narrow emission lines. (2) The UV light curve follows a shallower slope of $\propto t^{-0.91\pm 0.04}$ compared to that predicted by a tidal disruption event. We conjecture that a magnetic flux inversion event is the possible cause for this enigmatic event. (3) The compact radio emission which we tracked in the pre-CL (2014), during CL (2018) and post-CL(2021) at spatial scales $<1$ pc was at its lowest level during the changing look event in 2018, nearly contemporaneous with a low $2-10$ keV emission. The radio to X-ray ratio of the compact source $L_{\rm Radio}/L_{\rm X-ray}\sim 10^{-5.5}$, follows the Gudel-Benz relation, typically found in coronally active stars, and several AGN. (4) We do not detect any presence of nascent jets at the spatial scales of $\sim 5-10$ pc. △ Less

Submitted 14 March, 2022; originally announced March 2022.

Comments: Resubmitted to ApJ following minor comments from the referee

Unveiling the Universe with Emerging Cosmological Probes

Authors: Michele Moresco, Lorenzo Amati, Luca Amendola, Simon Birrer, John P. Blakeslee, Michele Cantiello, Andrea Cimatti, Jeremy Darling, Massimo Della Valle, Maya Fishbach, Claudio Grillo, Nico Hamaus, Daniel Holz, Luca Izzo, Raul Jimenez, Elisabeta Lusso, Massimo Meneghetti, Ester Piedipalumbo, Alice Pisani, Alkistis Pourtsidou, Lucia Pozzetti, Miguel Quartin, Guido Risaliti, Piero Rosati, Licia Verde

Abstract: The detection of the accelerated expansion of the Universe has been one of the major breakthroughs in modern cosmology. Several cosmological probes (CMB, SNe Ia, BAO) have been studied in depth to better understand the nature of the mechanism driving this acceleration, and they are being currently pushed to their limits, obtaining remarkable constraints that allowed us to shape the standard cosmol… ▽ More The detection of the accelerated expansion of the Universe has been one of the major breakthroughs in modern cosmology. Several cosmological probes (CMB, SNe Ia, BAO) have been studied in depth to better understand the nature of the mechanism driving this acceleration, and they are being currently pushed to their limits, obtaining remarkable constraints that allowed us to shape the standard cosmological model. In parallel to that, however, the percent precision achieved has recently revealed apparent tensions between measurements obtained from different methods. These are either indicating some unaccounted systematic effects, or are pointing toward new physics. Following the development of CMB, SNe, and BAO cosmology, it is critical to extend our selection of cosmological probes. Novel probes can be exploited to validate results, control or mitigate systematic effects, and, most importantly, to increase the accuracy and robustness of our results. This review is meant to provide a state-of-art benchmark of the latest advances in emerging beyond-standard cosmological probes. We present how several different methods can become a key resource for observational cosmology. In particular, we review cosmic chronometers, quasars, gamma-ray bursts, standard sirens, lensing time-delay with galaxies and clusters, cosmic voids, neutral hydrogen intensity mapping, surface brightness fluctuations, stellar ages of the oldest objects, secular redshift drift, and clustering of standard candles. The review describes the method, systematics, and results of each probe in a homogeneous way, giving the reader a clear picture of the available innovative methods that have been introduced in recent years and how to apply them. The review also discusses the potential synergies and complementarities between the various probes, exploring how they will contribute to the future of modern cosmology. △ Less

Submitted 19 December, 2022; v1 submitted 18 January, 2022; originally announced January 2022.

Comments: Invited review article for Living Reviews in Relativity. Accepted version. 191 pages, 54 figures, 11 tables

Fundamental differences in the properties of red and blue quasars: measuring the reddening and accretion properties with X-shooter

Authors: V. A. Fawcett, D. M. Alexander, D. J. Rosario, L. Klindt, E. Lusso, L. K. Morabito, G. Calistro Rivera

Abstract: We have recently found fundamental differences in the radio properties of red quasars when compared to typical blue quasars. In this paper we use X-shooter data, providing spectral coverage from $\sim 3000-25000$ Ang, of a sample of 40 red and blue luminous quasars at $1.45<z<1.65$ to explore the connections between the radio, emission-line, and accretion-disc properties. We fit various dust-extin… ▽ More We have recently found fundamental differences in the radio properties of red quasars when compared to typical blue quasars. In this paper we use X-shooter data, providing spectral coverage from $\sim 3000-25000$ Ang, of a sample of 40 red and blue luminous quasars at $1.45<z<1.65$ to explore the connections between the radio, emission-line, and accretion-disc properties. We fit various dust-extinction curves to the data and find that dust reddening can fully explain the observed colours for the majority of the red quasars in our sample, with moderate extinctions ranging from Av$\sim 0.06-0.7$ mags. We confront our spectra with a simple thin accretion-disc model and find this can describe the continua of both the blue and red quasars, once corrected for dust extinction; we also find no significant differences in the accretion properties. We detect ionized outflows in a number of red and blue quasars, but do not find any significant evidence that they are more prevalent in the red quasar population. Overall our findings imply that the radio emission is more closely connected to circumnuclear/ISM opacity rather than accretion disc or outflow differences. △ Less

Submitted 18 November, 2022; v1 submitted 11 January, 2022; originally announced January 2022.

Comments: 33 pages, 23 figures, 6 tables, accepted by MNRAS

A Multiwavelength Study of ELAN Environments (AMUSE$^2$). Mass budget, satellites spin alignment and gas infall in a massive $z\sim3$ quasar host halo

Authors: Fabrizio Arrigoni Battaia, Chian-Chou Chen, Hau-Yu Baobab Liu, Carlos De Breuck, Maud Galametz, Michele Fumagalli, Yujin Yang, Anita Zanella, Allison Man, Aura Obreja, J. Xavier Prochaska, Eduardo Bañados, Joseph F. Hennawi, Emanuele P. Farina, Martin A. Zwaan, Roberto Decarli, Elisabeta Lusso

Abstract: The systematic targeting of extended Ly$α$ emission around high-redshift quasars resulted in the discovery of rare and bright Enormous Ly$α$ Nebulae (ELANe) associated with multiple active galactic nuclei (AGN). We here initiate "a multiwavelength study of ELAN environments" (AMUSE$^2$) focusing on the ELAN around the $z\sim3$ quasar SDSS J1040+1020, a.k.a. the Fabulous ELAN. We report on VLT/HAWK… ▽ More The systematic targeting of extended Ly$α$ emission around high-redshift quasars resulted in the discovery of rare and bright Enormous Ly$α$ Nebulae (ELANe) associated with multiple active galactic nuclei (AGN). We here initiate "a multiwavelength study of ELAN environments" (AMUSE$^2$) focusing on the ELAN around the $z\sim3$ quasar SDSS J1040+1020, a.k.a. the Fabulous ELAN. We report on VLT/HAWK-I, APEX/LABOCA, JCMT/SCUBA-2, SMA/850$μ$m, ALMA/CO(5-4) and 2mm observations and compare them to previously published VLT/MUSE data. The continuum and line detections enable a first estimate of the star-formation rates, dust, stellar and molecular gas masses in four objects associated with the ELAN (three AGNs and one Ly$α$ emitter), confirming that the quasar host is the most star-forming (${\rm SFR}\sim500$ M$_\odot$ yr$^{-1}$) and massive galaxy ($M_{\rm star}\sim10^{11}$ M$_{\odot}$) in the system, and thus can be assumed as central. All four embedded objects have similar molecular gas reservoirs ($M_{\rm H_2}\sim10^{10}$ M$_{\odot}$), resulting in short depletion time scales. This fact together with the estimated total dark-matter halo mass, $M_{\rm DM}=(0.8-2)\times10^{13}$ M$_{\odot}$, implies that this ELAN will evolve into a giant elliptical galaxy. Consistently, the constraint on the baryonic mass budget for the whole system indicates that the majority of baryons should reside in a massive warm-hot reservoir (up to $10^{12}$ M$_{\odot}$), needed to complete the baryons count. Additionally, we discuss signatures of gas infall on the compact objects as traced by Ly$α$ radiative transfer effects and the evidence for the alignment between the satellites' spins and their directions to the central. △ Less

Submitted 30 November, 2021; originally announced November 2021.

Comments: 26 pages, 19 figures, 4 appendix; submitted to ApJ

A Multiwavelength Study of ELAN Environments (AMUSE$^2$): Ubiquitous dusty star-forming galaxies associated with enormous Ly$α$ nebulae on megaparsec scales

Authors: Marta Nowotka, Chian-Chou Chen, Fabrizio Arrigoni Battaia, Michele Fumagalli, Zheng Cai, Elisabeta Lusso, J. Xavier Prochaska, Yujin Yang

Abstract: We have been undertaking a systematic survey at 850 $μ$m based on a sample of four prototypical $z\sim2-3$ enormous Ly$α$ nebulae (ELANe) as well as their megaparsec-scale (Mpc-scale) environments to study the physical connections between ELANe and their coeval dusty submillimeter galaxies (SMGs). By analysing the SCUBA-2 data with self-consistent Monte Carlo simulations to construct the number co… ▽ More We have been undertaking a systematic survey at 850 $μ$m based on a sample of four prototypical $z\sim2-3$ enormous Ly$α$ nebulae (ELANe) as well as their megaparsec-scale (Mpc-scale) environments to study the physical connections between ELANe and their coeval dusty submillimeter galaxies (SMGs). By analysing the SCUBA-2 data with self-consistent Monte Carlo simulations to construct the number counts, here, we report on the overabundance of 850 $μ$m-selected submillimeter sources around all the four ELANe, by a factor of 3.6$\pm$0.6 (weighted average) compared to the blank fields. This suggests that the excessive number of submillimeter sources are likely to be part of the Mpc-scale environment around the ELANe, corroborating the co-evolution scenario for SMGs and quasars; this is a process which may be more commonly observed in the ELAN fields. If the current form of the underlying count models continues toward the fainter end, our results would suggest an excess of the 850 $μ$m extragalactic background light by a factor of between 2-10, an indication of significant background light fluctuations on the survey scales. Finally, by assuming that all the excessive submillimeter sources are associated with their corresponding ELAN environments, we estimate the SFR densities of each ELAN field, as well as a weighted average of $Σ$SFR=1200$\pm$300 $M_\odot$ yr$^{-1}$ Mpc$^{-3}$, consistent with that found in the vicinity of other quasar systems or proto-clusters at similar redshifts; in addition, it is a factor of about 300 greater than the cosmic mean. △ Less

Submitted 30 November, 2021; originally announced November 2021.

Comments: 11 pages, 5 pages, A&A in press

Journal ref: A&A 658, A77 (2022)

Simulating infrared spectro-photometric surveys with a SPRITZ

Authors: L. Bisigello, C. Gruppioni, F. Calura, A. Feltre, F. Pozzi, C. Vignali, L. Barchiesi, G. Rodighiero, M. Negrello, F. J. Carrera, K. M. Dasyra, J. A. Fernández-Ontiveros, M. Giard, E. Hatziminaoglou, H. Kaneda, E. Lusso, M. Pereira-Santaella, P. G. Pérez-González, C. Ricci, D. Schaerer, L. Spinoglio, L. Wang

Abstract: Mid- and far-infrared (IR) photometric and spectroscopic observations are fundamental to a full understanding of the dust-obscured Universe and the evolution of both star formation and black hole accretion in galaxies. In this work, using the specifications of the SPace Infrared telescope for Cosmology and Astrophysics (SPICA) as a baseline, we investigate the capability to study the dust-obscured… ▽ More Mid- and far-infrared (IR) photometric and spectroscopic observations are fundamental to a full understanding of the dust-obscured Universe and the evolution of both star formation and black hole accretion in galaxies. In this work, using the specifications of the SPace Infrared telescope for Cosmology and Astrophysics (SPICA) as a baseline, we investigate the capability to study the dust-obscured Universe of mid- and far-IR photometry at 34 and 70 $μ$m and low-resolution spectroscopy at 17-36 $μ$m using the state-of-the-art Spectro-Photometric Realisations of Infrared-selected Targets at all-z (SPRITZ) simulation. This investigation is also compared to the expected performance of the Origins Space Telescope and the Galaxy Evolution Probe. The photometric view of the Universe of a SPICA-like mission could cover not only bright objects (e.g. L$_{IR}$>10$^{12}$L$_\odot$) up to z=10, but also normal galaxies(L$_{IR}$<10$^{11}$L$_\odot$) up to z$\sim$4. At the same time, the spectroscopic observations of such mission could also allow us to estimate the redshifts and study the physical properties for thousands of star-forming galaxies and active galactic nuclei by observing the polycyclic aromatic hydrocarbons and a large set of IR nebular emission lines. In this way, a cold, 2.5-m size space telescope with spectro-photometric capability analogous to SPICA, could provide us with a complete three-dimensional (i.e. images and integrated spectra) view of the dust-obscured Universe and the physics governing galaxy evolution up to z$\sim$4. △ Less

Submitted 22 November, 2021; originally announced November 2021.

Comments: 22 pages, 17 figures, 4 tables, accepted for publication in PASA