-
MALLORN: Many Artificial LSST Lightcurves based on Observations of Real Nuclear transients
Authors:
Dylan Magill,
Matt Nicholl,
Vysakh Anilkumar,
Sjoert van Velzen,
Xinyue Sheng,
Thai Son Mai,
Hung Viet Tran,
Ngoc Phu Doan,
Thomas Moore,
Shubham Srivastav,
David R. Young,
Charlotte R. Angus,
Joshua Weston
Abstract:
The Vera C. Rubin Observatory's 10-Year Legacy Survey of Space and Time (LSST) is expected to produce a hundredfold increase in the number of transients we observe. However, there are insufficient spectroscopic resources to follow up on all of the wealth of targets that LSST will provide. As such it is necessary to be able to prioritise objects for followup observations or inclusion in sample stud…
▽ More
The Vera C. Rubin Observatory's 10-Year Legacy Survey of Space and Time (LSST) is expected to produce a hundredfold increase in the number of transients we observe. However, there are insufficient spectroscopic resources to follow up on all of the wealth of targets that LSST will provide. As such it is necessary to be able to prioritise objects for followup observations or inclusion in sample studies based purely on their LSST photometry. We are particularly keen to identify tidal disruption events (TDEs) with LSST. TDEs are immensely useful for determining black hole parameters and probing our understanding of accretion physics. To assist in these efforts, we present the Many Artificial LSST Lightcurves based on the Observations of Real Nuclear transients (MALLORN) data set and the corresponding classifier challenge for identifying TDEs. MALLORN comprises 10178 simulated LSST light curves, constructed from real Zwicky Transient Facility (ZTF) observations of 64 TDEs, 727 nuclear supernovae and 1407 AGN with spectroscopic labels using Gaussian process fitting, empirically-motivated spectral energy distributions from SNCosmo and the baseline from the Rubin Survey Simulator. Our novel approach can be easily adapted to simulate transients for any photometric survey using observations from another, requiring only the limiting magnitudes and an estimate of the cadence of observations. The MALLORN Astronomical Classification Challenge, launched on Kaggle on 15/10/2025, will allow competitors to test their photometric classifiers on simulated LSST data to find TDEs and improve upon their capabilities prior to the start of LSST.
△ Less
Submitted 4 December, 2025;
originally announced December 2025.
-
The role of prompt cusps in driving the core collapse of SIDM halos
Authors:
Vinh Tran,
Daniel Gilman,
M. Sten Delos,
Xuejian Shen,
Oliver Zier,
Mark Vogelsberger,
David Xu
Abstract:
Prompt cusps (PCs) form from the direct collapse of overdensities in the early Universe, reside at the center of every dark matter halo, and have density profiles steeper than $r^{-1}$ NFW cusps. Using a suite of high-resolution N-body simulations, we study the evolution of isolated halos in self-interacting dark matter (SIDM) with massive PCs embedded at their centers, a scenario that could be re…
▽ More
Prompt cusps (PCs) form from the direct collapse of overdensities in the early Universe, reside at the center of every dark matter halo, and have density profiles steeper than $r^{-1}$ NFW cusps. Using a suite of high-resolution N-body simulations, we study the evolution of isolated halos in self-interacting dark matter (SIDM) with massive PCs embedded at their centers, a scenario that could be realized in certain SIDM models with light mediators that predict a small-scale suppression of the linear matter power spectrum. We track the evolution of three equally concentrated $10^7\,{\rm{M}}_\odot$ halos, hosting PCs of various total masses, and quantify how the presence of a PC affects the processes of core formation and collapse. Early in the core-formation phase, halos with more prominent PCs exhibit a delayed evolution by a factor of $\sim 2$ due to smaller velocity dispersion gradients in the inner region. During most of the core-collapse phase, the halo evolution becomes closely aligned in physical time, with appropriate rescaling of densities, radii, and velocity dispersions. The scale densities and radii preserve the virial mass of the original halos, but with increased concentration. Deviations occur at the late phase of core-collapse at the level of $\sim 5\%$ relative to the reference collapse track of an NFW halo. These deviations depend non-trivially on both the increased concentration incurred by the PCs, as well as the velocity dispersion (temperature) of the outer halo regions, which can inhibit or enhance the heat transfer process. Our simulations illustrate the complex interplay between the inner and outer halo profiles in determining the onset of core collapse and motivate future studies in the full cosmological context.
△ Less
Submitted 28 November, 2025;
originally announced December 2025.
-
Non-Gaussianity in SMICA
Authors:
M. Citran,
H. V. Tran,
G. Patanchon,
B. van Tent
Abstract:
We develop a new formalism for the component separation method Spectral Matching Independent Component Analysis (SMICA) in order to include the information contained in the foregrounds beyond second-order statistics. We also develop a binned bispectrum estimator that works directly using maps of different frequency channels, capable of determining the bispectrum of multiple components at the same…
▽ More
We develop a new formalism for the component separation method Spectral Matching Independent Component Analysis (SMICA) in order to include the information contained in the foregrounds beyond second-order statistics. We also develop a binned bispectrum estimator that works directly using maps of different frequency channels, capable of determining the bispectrum of multiple components at the same time, shifting the traditional approach to non-Gaussianity estimation from a cleaned map to the component separation step, for a better handling of foreground uncertainty. We test our method on 400 E and B polarization simulations based on the LiteBIRD experiment, containing the two main sources of contamination for CMB polarization experiments: polarized dust and synchrotron emission. We show that the bispectrum does not improve the precision of the power spectrum estimation or of the spectral parameters. However, we are capable of recovering the correct 3-point correlator of the foregrounds and standard constraints on primordial non-Gaussianity in a coherent multi-frequency and multi-component framework. The advantage of our approach is that it combines data in an optimal way accounting for the power spectrum and the bispectrum of the various components, which is not true for the standard approach.
△ Less
Submitted 27 November, 2025;
originally announced November 2025.
-
Finding the boundary: Using galaxy membership to inform galaxy cluster extent through machine learning
Authors:
Christine Hao,
Stephanie O'Neil,
Mark Vogelsberger,
Vinh Tran,
Lamiya Mowla,
Joshua S. Speagle
Abstract:
The spatial extent of the environment's impact on galaxies marks a transitional region between cluster and field galaxies. We present a data-driven method to identify this region in galaxy clusters with masses $M_{200\rm ,mean}>10^{13} M_{\odot}$ at $z = 0$. Using resolved galaxy samples from the largest simulation volume of IllustrisTNG (TNG300-1), we examine how galaxy properties vary as a funct…
▽ More
The spatial extent of the environment's impact on galaxies marks a transitional region between cluster and field galaxies. We present a data-driven method to identify this region in galaxy clusters with masses $M_{200\rm ,mean}>10^{13} M_{\odot}$ at $z = 0$. Using resolved galaxy samples from the largest simulation volume of IllustrisTNG (TNG300-1), we examine how galaxy properties vary as a function of distance to the closest cluster. We train neural networks to classify galaxies into cluster and field galaxies based on their intrinsic properties. Using this classifier, we present the first quantitative and probabilistic map of the transition region. It is represented as a broad and intrinsically scattered region near cluster outskirts, rather than a sharp physical boundary. This is the physical detection of a mixed population. In order to determine transition regions of different physical processes by training property-specific models, we categorise galaxy properties based on their underlying physics, i.e. gas, stellar, and dynamical. Changes to the dynamical properties dominate the innermost regions of the clusters of all masses. Stellar properties and gas properties, on the other hand, exhibit transitions at similar locations for low mass clusters, yet gas properties have transitions in the outermost regions for high mass clusters. These results have implications for cluster environmental studies in both simulations and observations, particularly in refining the definition of cluster boundaries while considering environmental preprocessing and how galaxies evolve under the effect of the cluster environment.
△ Less
Submitted 10 November, 2025;
originally announced November 2025.
-
Core collapse in resonant self-interacting dark matter across two decades in halo mass
Authors:
Vinh Tran,
Xuejian Shen,
Daniel Gilman,
Mark Vogelsberger,
Stephanie O'Neil,
Donghua Xiong,
Jiayi Hu,
Ziang Wu
Abstract:
Core collapse, a process associated with self-interacting dark matter (SIDM) models, can increase the central density of halos by orders of magnitude with observable consequences for dwarf galaxy properties and gravitational lensing. Resonances in the self-interaction cross section, features of hidden-sector models with light mediators and attractive potentials, can boost the strength of self-inte…
▽ More
Core collapse, a process associated with self-interacting dark matter (SIDM) models, can increase the central density of halos by orders of magnitude with observable consequences for dwarf galaxy properties and gravitational lensing. Resonances in the self-interaction cross section, features of hidden-sector models with light mediators and attractive potentials, can boost the strength of self-interactions near specific relative velocities, accelerating collapse in halos with central velocity dispersions near the resonance. To explore this phenomenon, we present a suite of idealized N-body simulations of isolated halos with masses $10^7$-$10^9 \ \rm{M_\odot}$ evolved under two resonant cross section (RCS) models with localized enhancement to the cross section on scales $v \sim 5$-$50 \ \rm{km} \ \rm{s^{-1}}$. We show that the change in halo internal structure depends on how the velocity distribution of bound particles moves across resonances in the cross section during core formation and collapse. The interplay between the velocity distribution of bound particles and localized features of the cross section causes deviations from self-similar evolution, a characteristic of velocity-independent cross sections, at the level of up to $20\%$. Depending on the alignment with resonant features, halos of different masses reach different evolutionary stages after a fixed physical time and develop diverse density profiles and rotation curves.
△ Less
Submitted 2 October, 2025; v1 submitted 3 April, 2025;
originally announced April 2025.
-
An Upper Limit on the Interstellar Meteoroid Flux at Video Sizes from the Global Meteor Network
Authors:
Paul Wiegert,
Vanessa Tran,
Cole Gregg,
Denis Vida,
Peter Brown
Abstract:
Material arriving at our solar system from the Galaxy may be detected at Earth in the form of meteors ablating in our atmosphere. Here we report on a search for interstellar meteors within the highest-quality events in the Global Meteor Network (GMN) database. No events were detected that were conclusively hyperbolic with respect to the Sun; however, our search was not exhaustive and examined only…
▽ More
Material arriving at our solar system from the Galaxy may be detected at Earth in the form of meteors ablating in our atmosphere. Here we report on a search for interstellar meteors within the highest-quality events in the Global Meteor Network (GMN) database. No events were detected that were conclusively hyperbolic with respect to the Sun; however, our search was not exhaustive and examined only the top 57% of events, with a deeper examination planned for future work.
This study's effective meteoroid mass limit is 6.6 +/- 0.8 x 10^{-5} kg (5 millimeter diameter at a density of 1000 kg m^{-3}). Theoretical rates of interstellar meteors at these sizes range from 3 to 200 events globally per year. The highest rates can already be largely excluded by this study, while at the lowest rates GMN would have to observe for 25 more years to be 50% confident of seeing at least one event. GMN is thus well positioned to provide substantial constraints on the interstellar population at these sizes over the coming years. This study's results are statistically compatible with a rate of interstellar meteors at the Earth at less than 1 per million meteoroid impacts at Earth at millimeter sizes, or a flux rate of less than 8 +/- 2 x 10^{-11} per sq. km per hour at the 95% confidence level.
△ Less
Submitted 24 March, 2025;
originally announced March 2025.
-
Euclid Quick Data Release (Q1). Combined Euclid and Spitzer galaxy density catalogues at $z>$ 1.3 and detection of significant Euclid passive galaxy overdensities in Spitzer overdense regions
Authors:
Euclid Collaboration,
N. Mai,
S. Mei,
C. Cleland,
R. Chary,
J. G. Bartlett,
G. Castignani,
H. Dannerbauer,
G. De Lucia,
F. Fontanot,
D. Scott,
S. Andreon,
S. Bhargava,
H. Dole,
T. DUSSERRE,
S. A. Stanford,
V. P. Tran,
J. R. Weaver,
P. -A. Duc,
I. Risso,
N. Aghanim,
B. Altieri,
A. Amara,
N. Auricchio,
H. Aussel
, et al. (286 additional authors not shown)
Abstract:
Euclid will detect tens of thousands of clusters and protoclusters at $z$>1.3. With a total coverage of 63.1deg$^2$, the Euclid Quick Data Release 1 (Q1) is large enough to detect tens of clusters and hundreds of protoclusters at these early epochs. The Q1 photometric redshift catalogue enables us to detect clusters out to $z$ < 1.5; however, infrared imaging from Spitzer extends this limit to hig…
▽ More
Euclid will detect tens of thousands of clusters and protoclusters at $z$>1.3. With a total coverage of 63.1deg$^2$, the Euclid Quick Data Release 1 (Q1) is large enough to detect tens of clusters and hundreds of protoclusters at these early epochs. The Q1 photometric redshift catalogue enables us to detect clusters out to $z$ < 1.5; however, infrared imaging from Spitzer extends this limit to higher redshifts by using high local projected densities of Spitzer-selected galaxies as signposts for cluster and protocluster candidates. We use Spitzer imaging of the Euclid Deep Fields (EDFs) to derive densities for a sample of Spitzer-selected galaxies at redshifts $z$ > 1.3, building Spitzer IRAC1 and IRAC2 photometric catalogues that are 95% complete at a magnitude limit of IRAC2=22.2, 22.6, and 22.8 for the EDF-S, EDF-F, and EDF-N, respectively. We apply two complementary methods to calculate galaxy densities: (1) aperture and surface density; and (2) the Nth-nearest-neighbour method. When considering a sample selected at a magnitude limit of IRAC2 < 22.2, at which all three EDFs are 95% complete, our surface density distributions are consistent among the three EDFs and with the SpUDS blank field survey. We also considered a deeper sample (IRAC2 < 22.8), finding that 2% and 3% of the surface densities in the North and Fornax fields are 3$σ$ higher than the average field distribution and similar to densities found in the CARLA cluster survey. Our surface densities are also consistent with predictions from the GAEA semi-analytical model. Using combined Euclid and ground-based i-band photometry we show that our highest Spitzer-selected galaxy overdense regions, found at $z$~1.5, also host high densities of passive galaxies. This means that we measure densities consistent with those found in clusters and protoclusters at $z$>1.3.
△ Less
Submitted 20 March, 2025; v1 submitted 19 March, 2025;
originally announced March 2025.
-
A Novel Density Profile for Isothermal Cores of Dark Matter Halos
Authors:
Vinh Tran,
Xuejian Shen,
Mark Vogelsberger,
Daniel Gilman,
Stephanie O'Neil,
Cian Roche,
Oliver Zier,
Jiarun Gao
Abstract:
We present a novel analytic density profile for halos in self-interacting dark matter (SIDM) models, which accurately captures the isothermal-core configuration, i.e. where both the density and velocity dispersion profiles exhibit central plateaus in the halo innermost region. Importantly, the profile retains a simple and tractable functional form. We demonstrate analytically how our density profi…
▽ More
We present a novel analytic density profile for halos in self-interacting dark matter (SIDM) models, which accurately captures the isothermal-core configuration, i.e. where both the density and velocity dispersion profiles exhibit central plateaus in the halo innermost region. Importantly, the profile retains a simple and tractable functional form. We demonstrate analytically how our density profile satisfies the aforementioned conditions, with comparisons to other contemporary functional choices. We further validate the profile using idealized N-body simulations, showing that it provides excellent representations of both the density and velocity dispersion profiles across a broad range of evolutionary stages, from the early thermalization phase to the late core-collapse regime. As a result of its accuracy and simplicity, the proposed profile offers a robust framework for analyzing halo evolution in a variety of SIDM scenarios. It also holds practical utility in reducing simulation needs and in generating initial conditions for simulations targeting the deep core-collapse regime.
△ Less
Submitted 18 November, 2025; v1 submitted 18 November, 2024;
originally announced November 2024.
-
Analytic bounds on late-time axion-scalar cosmologies
Authors:
Gary Shiu,
Flavio Tonioni,
Hung V. Tran
Abstract:
The cosmological dynamics of multiple scalar/pseudoscalar fields are difficult to solve, especially when the field-space metric is curved. This presents a challenge in determining whether a given model can support cosmic acceleration, without solving for the on-shell solution. In this work, we present bounds on late-time FLRW-cosmologies in classes of theories that involve arbitrary numbers of sca…
▽ More
The cosmological dynamics of multiple scalar/pseudoscalar fields are difficult to solve, especially when the field-space metric is curved. This presents a challenge in determining whether a given model can support cosmic acceleration, without solving for the on-shell solution. In this work, we present bounds on late-time FLRW-cosmologies in classes of theories that involve arbitrary numbers of scalar and pseudoscalar fields coupled both kinetically (leading to a curved field space metric) and through scalar potentials. Such bounds are proven analytically, independently of initial conditions, with no approximation in the field equations and without referring to explicit solutions. Besides their broad applications to cosmological model building, our bounds can be applied to studying asymptotic cosmologies of certain classes of string compactifications.
△ Less
Submitted 20 September, 2024; v1 submitted 24 June, 2024;
originally announced June 2024.
-
Gravothermal Catastrophe in Resonant Self-interacting Dark Matter Models
Authors:
Vinh Tran,
Daniel Gilman,
Mark Vogelsberger,
Xuejian Shen,
Stephanie O'Neil,
Xinyue Zhang
Abstract:
We investigate a self-interacting dark matter (SIDM) model featuring a velocity-dependent cross section with an order-of-magnitude resonant enhancement of the cross section at $\sim 16\,{\rm km}\,{\rm s}^{-1}$. To understand the implications for the structure of dark matter halos, we perform N-body simulations of isolated dark matter halos of mass $\sim 10^8\,{\rm M}_\odot$, a halo mass selected t…
▽ More
We investigate a self-interacting dark matter (SIDM) model featuring a velocity-dependent cross section with an order-of-magnitude resonant enhancement of the cross section at $\sim 16\,{\rm km}\,{\rm s}^{-1}$. To understand the implications for the structure of dark matter halos, we perform N-body simulations of isolated dark matter halos of mass $\sim 10^8\,{\rm M}_\odot$, a halo mass selected to have a maximum response to the resonance. We track the core formation and the gravothermal collapse phases of the dark matter halo in this model and compare the halo evolving with the resonant cross section with halos evolving with velocity-independent cross sections. We show that dark matter halo evolution with the resonant cross section exhibits a deviation from universality that characterizes halo evolution with velocity-independent cross sections. The halo evolving under the influence of the resonance reaches a lower minimum central density during core formation. It subsequently takes about $20\%$ longer to reach its initial central density during the collapse phase. These results motivate a more detailed exploration of halo evolution in models with pronounced resonances.
△ Less
Submitted 30 August, 2024; v1 submitted 3 May, 2024;
originally announced May 2024.
-
Self-interacting Vectorial Dark Matter in a SM-like Dark Sector
Authors:
Van Que Tran,
Thong T. Q. Nguyen,
Tzu-Chiang Yuan
Abstract:
A $SU(2)_D \times U(1)_D$ gauge-Higgs sector, an exact dark copy of the Standard Model (SM) one, is proposed. It is demonstrated that the dark gauge bosons ${\cal W}^{(p,m)}$, in analogous to the SM $W^\pm$, can fulfill the role as a self-interacting vector dark matter candidate, solving the core versus cusp and missing satellites problems faced by the conventional paradigm of collisionless weakly…
▽ More
A $SU(2)_D \times U(1)_D$ gauge-Higgs sector, an exact dark copy of the Standard Model (SM) one, is proposed. It is demonstrated that the dark gauge bosons ${\cal W}^{(p,m)}$, in analogous to the SM $W^\pm$, can fulfill the role as a self-interacting vector dark matter candidate, solving the core versus cusp and missing satellites problems faced by the conventional paradigm of collisionless weakly interacting massive particle. Constraints from collider, astroparticle and cosmology on such a self-interacting vector dark matter candidate are scrutinized. Implications for the future searches of ${\cal W}^{(p,m)}$ in direct detection experiments are discussed.
△ Less
Submitted 17 December, 2023;
originally announced December 2023.
-
Collapsing universe before time
Authors:
Gary Shiu,
Flavio Tonioni,
Hung V. Tran
Abstract:
In this note, we prove analytic bounds on the equation of state of a cosmological fluid composed of an arbitrary number of canonical scalars evolving in a negative multi-exponential potential. Because of the negative energy, the universe is contracting and eventually undergoes a big crunch. A contracting universe is a fundamental feature of models of ekpyrosis and cyclic universes, which are a pro…
▽ More
In this note, we prove analytic bounds on the equation of state of a cosmological fluid composed of an arbitrary number of canonical scalars evolving in a negative multi-exponential potential. Because of the negative energy, the universe is contracting and eventually undergoes a big crunch. A contracting universe is a fundamental feature of models of ekpyrosis and cyclic universes, which are a proposed alternative to cosmic inflation to solve the flatness and horizon problems. Our analytic bounds set quantitative constraints on general effective theories of ekpyrosis. When applied to specific top-down constructions, our bounds can be used to determine whether ekpyrosis could in principle be realized. We point out some possible sources of tension in realizing the ekpyrotic universe in controlled constructions of string theory.
△ Less
Submitted 30 May, 2024; v1 submitted 11 December, 2023;
originally announced December 2023.
-
WTP$\,$10aaauow: Discovery of a new FU Ori outburst towards the RCW$\,$49 star-forming region in NEOWISE data
Authors:
Vinh Tran,
Kishalay De,
Lynne Hillenbrand
Abstract:
Large-amplitude accretion outbursts in young stars are expected to play a central role in proto-stellar assembly. Outburst identification historically has taken place using optical techniques, but recent, systematic infrared searches are enabling their discovery in heavily dust-obscured regions of the Galactic plane. Here, we present the discovery of WTP$\,$10aaauow, a large-amplitude mid-infrared…
▽ More
Large-amplitude accretion outbursts in young stars are expected to play a central role in proto-stellar assembly. Outburst identification historically has taken place using optical techniques, but recent, systematic infrared searches are enabling their discovery in heavily dust-obscured regions of the Galactic plane. Here, we present the discovery of WTP$\,$10aaauow, a large-amplitude mid-infrared (MIR) outburst identified in a systematic search of NEOWISE data using new image subtraction techniques. The source is located towards the RCW$\,$49 star-forming region, and estimated to be at a distance of $\approx 4\,$kpc via Gaia parallax measurement. Concurrent with the MIR brightening, the source underwent a $\gtrsim5\,$mag outburst in the optical and near-infrared (NIR) bands, reaching a peak luminosity of $\approx260\,$L$_\odot$ in 2014-2015, followed by a slow decline over the next 7 years. Analysis of the pre- and post-outburst spectral energy distributions reveal a pre-outburst stellar photosphere at a temperature of $3600-4000\,$K, surrounded by a likely two-component dust structure similar to a flat-spectrum or Class I type YSO. We present optical and NIR spectroscopy that show a GK-type spectrum in the optical bands exhibiting complex line profiles in strong absorption features, and evidence for a wind reaching a terminal velocity of $\approx 400\,$km$\,$s$^{-1}$. The NIR bands are characterized by a cooler M-type spectrum exhibiting a forest of atomic and molecular features. All together, the spectra demonstrate that WTP$\,$10aaauow is an FU Ori type outburst. Ongoing systematic infrared searches will continue to reveal the extent of this population in the Galactic disk.
△ Less
Submitted 2 May, 2024; v1 submitted 16 October, 2023;
originally announced October 2023.
-
Late-time attractors and cosmic acceleration
Authors:
Gary Shiu,
Flavio Tonioni,
Hung V. Tran
Abstract:
We prove the conditions under which scaling cosmologies are inevitable late-time attractors of multi-field multi-exponential potentials, independently of initial conditions. The advantage of such scaling cosmologies is that the time dependence of the fields and of the scale factor is known analytically, thus allowing late-time observables to be determined exactly. Expanding the earlier results of…
▽ More
We prove the conditions under which scaling cosmologies are inevitable late-time attractors of multi-field multi-exponential potentials, independently of initial conditions. The advantage of such scaling cosmologies is that the time dependence of the fields and of the scale factor is known analytically, thus allowing late-time observables to be determined exactly. Expanding the earlier results of ref. arXiv:hep-th/2303.03418, here we continue the program of analytically characterizing the late-time behavior of cosmological solutions. Our results are general in that they are derived without relying on any approximation nor are they based on any assumption on the sources of the potential, such as their higher-dimensional or string-theoretic origin. We point out a number of model-independent features that follow from our analytic results, including a convex-hull criterion for cosmic acceleration. When applied to string theory, our analytic knowledge of late-time cosmological solutions enables us to single out potentials that can describe an accelerating universe from those which cannot and to quantitatively test several conjectured Swampland criteria.
△ Less
Submitted 22 September, 2023; v1 submitted 12 June, 2023;
originally announced June 2023.
-
Different higher-order kinematics between star-forming and quiescent galaxies based on the SAMI, MAGPI and LEGA-C surveys
Authors:
Francesco D'Eugenio,
Arjen van der Wel,
Caro Derkenne,
Josha van Houdt,
Rachel Bezanson,
Edward N. Taylor,
Jesse van de Sande,
William M. Baker,
Eric F. Bell,
Joss Bland-Hawthorn,
Asa F. L. Bluck,
Sarah Brough,
Julia J. Bryant,
Matthew Colless,
Luca Cortese,
Scott M. Croom,
Pieter van Dokkum,
Deanne Fisher,
Caroline Foster,
Amelia Fraser-McKelvie,
Anna Gallazzi,
Anna de Graaff,
Brent Groves,
Claudia del P. Lagos,
Tobias J. Looser
, et al. (16 additional authors not shown)
Abstract:
We present the first statistical study of spatially integrated non-Gaussian stellar kinematics spanning 7 Gyr in cosmic time. We use deep, rest-frame optical spectroscopy of massive galaxies (stellar mass $M_\star > 10^{10.5} {\rm M}_\odot$) at redshifts z = 0.05, 0.3 and 0.8 from the SAMI, MAGPI and LEGA-C surveys, to measure the excess kurtosis $h_4$ of the stellar velocity distribution, the lat…
▽ More
We present the first statistical study of spatially integrated non-Gaussian stellar kinematics spanning 7 Gyr in cosmic time. We use deep, rest-frame optical spectroscopy of massive galaxies (stellar mass $M_\star > 10^{10.5} {\rm M}_\odot$) at redshifts z = 0.05, 0.3 and 0.8 from the SAMI, MAGPI and LEGA-C surveys, to measure the excess kurtosis $h_4$ of the stellar velocity distribution, the latter parametrised as a Gauss-Hermite series. We find that at all redshifts where we have large enough samples, $h_4$ anti-correlates with the ratio between rotation and dispersion, highlighting the physical connection between these two kinematic observables. In addition, and independently from the anti-correlation with rotation-to-dispersion ratio, we also find a correlation between $h_4$ and $M_\star$, potentially connected to the assembly history of galaxies. In contrast, after controlling for mass, we find no evidence of independent correlation between $h_4$ and aperture velocity dispersion or galaxy size. These results hold for both star-forming and quiescent galaxies. For quiescent galaxies, $h_4$ also correlates with projected shape, even after controlling for the rotation-to-dispersion ratio. At any given redshift, star-forming galaxies have lower $h_4$ compared to quiescent galaxies, highlighting the link between kinematic structure and star-forming activity.
△ Less
Submitted 7 March, 2023;
originally announced March 2023.
-
Accelerating universe at the end of time
Authors:
Gary Shiu,
Flavio Tonioni,
Hung V. Tran
Abstract:
We investigate whether an accelerating universe can be realized as an asymptotic late-time solution of FLRW-cosmology with multi-field multi-exponential potentials. Late-time cosmological solutions exhibit a universal behavior which enables us to bound the rate of time variation of the Hubble parameter. In string-theoretic realizations, if the dilaton remains a rolling field, our bound singles out…
▽ More
We investigate whether an accelerating universe can be realized as an asymptotic late-time solution of FLRW-cosmology with multi-field multi-exponential potentials. Late-time cosmological solutions exhibit a universal behavior which enables us to bound the rate of time variation of the Hubble parameter. In string-theoretic realizations, if the dilaton remains a rolling field, our bound singles out a tension in achieving asymptotic late-time cosmic acceleration. Our findings go beyond previous no-go theorems in that they apply to arbitrary multi-exponential potentials and make no specific reference to vacuum or slow-roll solutions. We also show that if the late-time solution approaches a critical point of the dynamical system governing the cosmological evolution, the criterion for cosmic acceleration can be generally stated in terms of a directional derivative of the potential.
△ Less
Submitted 21 September, 2023; v1 submitted 6 March, 2023;
originally announced March 2023.
-
g-mode Oscillations in Neutron Stars with Hyperons
Authors:
Vinh Tran,
Suprovo Ghosh,
Nicholas Lozano,
Debarati Chatterjee,
Prashanth Jaikumar
Abstract:
A common alternative to the standard assumption of nucleonic composition of matter in the interior of a neutron star is to include strange baryons, particularly hyperons. Any change in composition of the neutron star core has an effect on g-mode oscillations of neutron stars, through the compositional dependence of the equilibrium and adiabatic sound speeds. We study the core g-modes of a neutron…
▽ More
A common alternative to the standard assumption of nucleonic composition of matter in the interior of a neutron star is to include strange baryons, particularly hyperons. Any change in composition of the neutron star core has an effect on g-mode oscillations of neutron stars, through the compositional dependence of the equilibrium and adiabatic sound speeds. We study the core g-modes of a neutron star contaning hyperons, using a variety of relativistic mean field models of dense matter that satisfy observational constraints on global properties of neutron stars. Our selected models predict a sharp rise in the g-mode frequencies upon the onset of strange baryons. Should g-modes be observed in the near future, their frequency could be used to test the presence of hyperonic matter in the core of neutron stars.
△ Less
Submitted 19 December, 2022;
originally announced December 2022.
-
Temperature Effects on Core g-modes of Neutron Stars
Authors:
Nicholas Lozano,
Vinh Tran,
Prashanth Jaikumar
Abstract:
Neutron stars provide a unique physical laboratory to study the properties of matter at high density. We study a diagnostic of the composition of high-density matter, namely, g-mode oscillations, which are driven by buoyancy forces. These oscillations can be excited by tidal forces and couple to gravitational waves. We extend prior results for the g-mode spectrum of cold neutron star matter to tem…
▽ More
Neutron stars provide a unique physical laboratory to study the properties of matter at high density. We study a diagnostic of the composition of high-density matter, namely, g-mode oscillations, which are driven by buoyancy forces. These oscillations can be excited by tidal forces and couple to gravitational waves. We extend prior results for the g-mode spectrum of cold neutron star matter to temperatures that are expected to be achieved in neutron star mergers using a parameterization for finite-temperature effects recently proposed by Raithel, Özel and Psaltis. We find that the g-modes of canonical mass neutron stars ($\approx$1.4$M_{\odot}$) are suppressed at high temperature, and core $g$-modes are supported only in the most massive ($\geq $2$M_{\odot}$) of hot neutron stars.
△ Less
Submitted 17 July, 2022;
originally announced July 2022.
-
Confronting dark matter co-annihilation of Inert two Higgs Doublet Model with a compressed mass spectrum
Authors:
Chih-Ting Lu,
Van Que Tran,
Yue-Lin Sming Tsai
Abstract:
We perform a comprehensive analysis for the light scalar dark matter (DM)in the Inert two Higgs doublet model (i2HDM) with compressed mass spectra, small mass splittings among three $\mathbb{Z}_2$ odd particles---scalar $S$, pseudo-scalar $A$, and charged Higgs $H^\pm$. In such a case, the co-annihilation processes play a significant role to reduce DM relic density. As long as a co-annihilation go…
▽ More
We perform a comprehensive analysis for the light scalar dark matter (DM)in the Inert two Higgs doublet model (i2HDM) with compressed mass spectra, small mass splittings among three $\mathbb{Z}_2$ odd particles---scalar $S$, pseudo-scalar $A$, and charged Higgs $H^\pm$. In such a case, the co-annihilation processes play a significant role to reduce DM relic density. As long as a co-annihilation governs the total interaction rate in the early universe, a small annihilation rate is expected to reach a correct DM relic density and its coupling $λ_S$ between DM pair and Higgs boson shall be tiny. Consequently, a negligible DM-nucleon elastic scattering cross section is predicted at the tree-level. In this work, we include the one-loop quantum corrections of the DM-nucleon elastic scattering cross section. We found that the quartic self-coupling $λ_2$ between $\mathbb{Z}_2$ odd particles indeed contributes to the one-loop quantum correction and behaves non-trivially for the co-annihilation scenario. Interestingly, the parameter space, which is allowed by the current constraints considered in this study, can predict the DM mass and annihilation cross section at the present compatible with the AMS-02 antiproton excess. The parameter space can be further probed at the future high luminosity LHC.
△ Less
Submitted 2 June, 2020; v1 submitted 18 December, 2019;
originally announced December 2019.
-
On the Gas Content, Star Formation Efficiency, and Environmental Quenching of Massive Galaxies in Proto-Clusters at z~2.0-2.5
Authors:
Jorge A. Zavala,
C. M. Casey,
J. B. Champagne,
Y. Chiang,
H. Dannerbauer,
P. Drew,
H. Fu,
J. Spilker,
L. Spitler,
K. V. Tran,
E. Treister,
S. Toft
Abstract:
We present ALMA Band 6 (nu=233GHz, lambda=1.3mm) continuum observations towards 68 'normal' star-forming galaxies within two Coma-like progenitor structures at z=2.10 and 2.47, from which ISM masses are derived, providing the largest census of molecular gas mass in overdense environments at these redshifts. Our sample comprises galaxies with a stellar mass range of 1x10^9M_sun - 4x10^11M_sun with…
▽ More
We present ALMA Band 6 (nu=233GHz, lambda=1.3mm) continuum observations towards 68 'normal' star-forming galaxies within two Coma-like progenitor structures at z=2.10 and 2.47, from which ISM masses are derived, providing the largest census of molecular gas mass in overdense environments at these redshifts. Our sample comprises galaxies with a stellar mass range of 1x10^9M_sun - 4x10^11M_sun with a mean M_*~6x10^10M_sun. Combining these measurements with multiwavelength observations and SED modeling, we characterize the gas mass fraction and the star formation efficiency, and infer the impact of the environment on galaxies' evolution. Most of our detected galaxies (~70%) have star formation efficiencies and gas fractions similar to those found for coeval field galaxies and in agreement with the field scaling relations. However, we do find that the proto-clusters contain an increased fraction of massive, gas-poor galaxies, with low gas fractions (f_gas<6-10%) and red rest-frame ultraviolet/optical colors typical of post-starburst and passive galaxies. The relatively high abundance of passive galaxies suggests an accelerated evolution of massive galaxies in proto-cluster environments. The large fraction of quenched galaxies in these overdense structures also implies that environmental quenching takes place during the early phases of cluster assembly, even before virialization. From our data, we derive a quenching efficiency of E_q~0.45 and an upper limit on the quenching timescale of T_q<1Gyr.
△ Less
Submitted 29 October, 2019;
originally announced October 2019.
-
Deriving a multivariate CO-to-H$_2$ conversion function using the [CII]/CO(1-0) ratio and its application to molecular gas scaling relations
Authors:
G. Accurso,
A. Saintonge,
B. Catinella,
L. Cortese,
R. Dave,
S. H. Dunsheath,
R. Genzel,
J. Gracia-Carpio,
T. M. Heckman,
Jimmy,
C. Kramer,
Cheng Li,
K. Lutz,
D. Schiminovich,
K. Schuster,
A. Sternberg,
E. Sturm,
L. J. Tacconi,
K. V. Tran,
J. Wang
Abstract:
We present Herschel PACS observations of the [CII] 158 micron emission line in a sample of 24 intermediate mass (9<logM$_\ast$/M$_\odot$<10) and low metallicity (0.4< Z/Z$_\odot$<1.0) galaxies from the xCOLD GASS survey. Combining them with IRAM CO(1-0) measurements, we establish scaling relations between integrated and molecular region [CII]/CO(1-0) luminosity ratios as a function of integrated g…
▽ More
We present Herschel PACS observations of the [CII] 158 micron emission line in a sample of 24 intermediate mass (9<logM$_\ast$/M$_\odot$<10) and low metallicity (0.4< Z/Z$_\odot$<1.0) galaxies from the xCOLD GASS survey. Combining them with IRAM CO(1-0) measurements, we establish scaling relations between integrated and molecular region [CII]/CO(1-0) luminosity ratios as a function of integrated galaxy properties. A Bayesian analysis reveals that only two parameters, metallicity and offset from the star formation main sequence, $Δ$MS, are needed to quantify variations in the luminosity ratio; metallicity describes the total dust content available to shield CO from UV radiation, while $Δ$MS describes the strength of this radiation field. We connect the [CII]/CO luminosity ratio to the CO-to-H$_2$ conversion factor and find a multivariate conversion function $α_{CO}$, which can be used up to z~2.5. This function depends primarily on metallicity, with a second order dependence on $Δ$MS. We apply this to the full xCOLD GASS and PHIBSS1 surveys and investigate molecular gas scaling relations. We find a flattening of the relation between gas mass fraction and stellar mass at logM$_\ast$/M$_\odot$<10. While the molecular gas depletion time varies with sSFR, it is mostly independent of mass, indicating that the low L$_{CO}$/SFR ratios long observed in low mass galaxies are entirely due to photodissociation of CO, and not to an enhanced star formation efficiency.
△ Less
Submitted 9 February, 2017;
originally announced February 2017.
-
Dark Sectors 2016 Workshop: Community Report
Authors:
Jim Alexander,
Marco Battaglieri,
Bertrand Echenard,
Rouven Essig,
Matthew Graham,
Eder Izaguirre,
John Jaros,
Gordan Krnjaic,
Jeremy Mardon,
David Morrissey,
Tim Nelson,
Maxim Perelstein,
Matt Pyle,
Adam Ritz,
Philip Schuster,
Brian Shuve,
Natalia Toro,
Richard G Van De Water,
Daniel Akerib,
Haipeng An,
Konrad Aniol,
Isaac J. Arnquist,
David M. Asner,
Henning O. Back,
Keith Baker
, et al. (179 additional authors not shown)
Abstract:
This report, based on the Dark Sectors workshop at SLAC in April 2016, summarizes the scientific importance of searches for dark sector dark matter and forces at masses beneath the weak-scale, the status of this broad international field, the important milestones motivating future exploration, and promising experimental opportunities to reach these milestones over the next 5-10 years.
This report, based on the Dark Sectors workshop at SLAC in April 2016, summarizes the scientific importance of searches for dark sector dark matter and forces at masses beneath the weak-scale, the status of this broad international field, the important milestones motivating future exploration, and promising experimental opportunities to reach these milestones over the next 5-10 years.
△ Less
Submitted 30 August, 2016;
originally announced August 2016.