arXiv subjects

Malgorzata Siudek

Publications and source records attributed to Malgorzata Siudek.

At least 19 recordsLinked to original sources

arXiv2026

Tracing the Cosmic Evolution of the Cool Circumgalactic Medium of Luminous Red Galaxies with DESI Year 1 Data

We investigate the properties of the cool circumgalactic medium (CGM) of massive galaxies and their cosmic evolution. By using the year 1 dataset of luminous red galaxies (LRGs) and QSOs from the Dark Energy Spectroscopic Instrument survey, we construct a sample of approximately 800,000 galaxy-quasar pairs and measure the radial distribution and kinematics of the cool gas traced by Mg II absorption lines as a function of galaxy properties from redshift 0.4 to redshift 1.2. Our results show that the covering fraction of the cool gas around LRGs increases with redshift, following a trend similar to the global evolution of galaxy star formation rate. At small radii (< 0.3rvir), the covering fraction anti-correlates with stellar mass, suggesting that mass-dependent processes suppress the cool gas content in the inner region. In addition, we measure the gas dispersion by modeling the velocity distribution of absorbers with a narrow and a broad components -- sigma_n ~ 160 and sigma_b ~ 380 km/s -- and quantify their relative contributions. The results show that the broad component becomes more prominent in the outer region, and its relative importance in the central region grows with increasing stellar mass. Finally, we discuss possible origins of the cool gas around massive galaxies, including the contribution of satellite galaxies and the precipitation scenario.

astro-ph.GA↗

arXiv2026

E-INSPIRE - II. Finding relics from wide-sky multi-band surveys: A proof-of-concept machine learning regression algorithm

In this second paper of the E-INSPIRE series, we train a machine-learning-based regression on $\sim430$ nearby ($z<0.5$) ultra-compact massive galaxies (UCMGs) with spectroscopically inferred kinematics, stellar population parameters and a measured ``degree of relicness'' (DoR). Our goal is to investigate how robustly the spectroscopically inferred DoR can be statistically reconstructed from observable galaxy properties, and to explore the potential applicability of this framework to future wide-area surveys. We test several regression algorithms finding that Support Vector Regression (SVR) provides the best performance. We explore multiple input feature configurations, from a minimal set including only age and metallicity to more comprehensive ones incorporating stellar population parameters, kinematics, structural properties, and the associated uncertainties. All tested models achieve similarly high performance on the training set ($R^2\ge0.81$), except for the minimal configuration ($R^2\sim0.78$). When evaluated on an independent INSPIRE sample of 52 UCMGs, the predictive power remains robust, although with increased model-to-model variation. The DoR distribution shows three regimes, with low (DoR$<0.3$) and high (DoR$>0.6$) values sparsely populated, leading to mild regression shrinkage toward intermediate values. However, this behaviour enables a conservative selection strategy: galaxies with predicted DoR$\ge0.6$ are strongly biased toward genuine extreme relics, making them prime targets for follow-up observations. This proof-of-concept confirms that the spectroscopically inferred DoR is robustly connected to observable stellar population and kinematical properties, and provides a first step toward future relic-candidate selection strategies in large photometric and spectroscopic surveys.

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arXiv2026

First detection of ultra-fast outflows in a quiescent galaxy

Outflows in active galactic nuclei (AGN) are recognized as a fundamental mechanism driving the co-evolution of supermassive black holes (SMBHs) and their host galaxies. Although powerful outflows are frequently detected in gas-rich, active star-forming galaxies, their existence and potential impact within gas-poor, quiescent galaxies remain poorly understood. We report the first detection of a powerful ultra-fast outflow (UFO) in a nearby quiescent galaxy KUG 1208+386, providing a multiscale analysis of AGN winds from nuclear to galactic scales. We detect a nuclear X-ray UFO with a velocity of $v_{out} \approx -0.07c$ and a kinetic power of $\dot{E}_{\rm UFO}=(0.8\mbox{--}6.5) \times 10^{43}$erg/s, sufficient to drive effective AGN feedback ($\dot{E}_{\rm UFO}/L_\mathrm{Edd}=(1\mbox{--}8)\%$) and far exceeding the galactic [OIII] outflow power $\sim 10^{40}$ erg/s. Host galaxy analysis reveals a massive quiescent system (specific star formation rate $\sim3\times10^{-12}\mathrm{yr}^{-1}$) that has been quenched $\sim$9 Gyr ago. The central AGN is obscured by a line-of-sight (LOS) column density of $\log (N_\mathrm{H}^\mathrm{LOS}/\mathrm{cm}^{-2})\sim23$ and the circumnuclear scattering material is Compton-thick $\log(N_\mathrm{H}^\mathrm{scatter}/\mathrm{cm}^{-2})=24.7^{+0.8}_{-0.5}$. The discovery of a nuclear UFO in a long-quenched massive galaxy challenges the paradigm that UFOs are exclusive to gas-rich, star-forming systems, suggesting instead that they are governed by the local circumnuclear environments, rather than the global gas reservoir. Our results indicate that episodic, powerful winds can maintain the quiescent state of KUG 1208+386 over Gyr timescales, supporting a wind-driven `maintenance' mode of AGN feedback that is distinct from the classical jet mode.

astro-ph.GA↗

arXiv2026

Deep Extragalactic VIsible Legacy Survey (DEVILS): Morphologically-selected galaxy merger fractions and their direct comparison to close-pair samples

Galaxy mergers are a central driver of galaxy evolution across cosmic time, and thus, quantifying their frequency is critical for constraining hierarchical models of galaxy formation. Motivated by the need to robustly quantify these fractions and their evolution, we build on our previous close-pair analysis by exploring morphological identification techniques within the Deep Extragalactic VIsible Legacy Survey (DEVILS), using the D10 (COSMOS) field, which covers an area of $1.47$ deg$^2$. While close-pairs trace the early stages of galaxy interactions, morphological methods probe more advanced phases of the merging process, including systems with disturbed structures and post-merger remnants. We present galaxy merger fractions over the redshift range $0.2 < z < 0.9$ using visual classification and automated identification based on non-parametric statistics: concentration ($C$), asymmetry ($A$), smoothness ($S$), Gini ($G$), and $M_{20}$, applied to HST/ACS imaging. To enhance the detection of subtle structural perturbations, we measure asymmetry on unsharp-masked images. We find relatively little overlap between visually and automatically identified samples, which highlights their distinct sensitivities and limitations. Moreover, galaxy merger fractions derived from morphological disturbances are consistently higher than those from close-pair counts at all redshifts. This potentially reflects how each method probes different stages of the merger process, with distinct observability timescales, as well as the fact that morphologically disturbed galaxies, at a given redshift, are typically the later-stage descendants of close-pairs from earlier epochs. This comparison allows us to examine systematic differences between identification techniques and assess how they impact the observed evolution of the galaxy merger fraction.

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arXiv2026

Towards Bayesian Photometric Cosmic Chronometers: Application to VIPERS

The cosmic chronometer (CC) method provides a direct measurement of the expansion history, $H(z)$, from the differential ages of passively evolving galaxies. However, most CC analyses rely on high-quality spectroscopy to select passive galaxies, measure age-sensitive spectral features, and control stellar-population systematics. We build on existing works that use the D4000 spectral break as a proxy for measuring galaxy ages and apply it to a photometry-selected galaxy sample from VIPERS PDR2 in the range $0.5 \le z \le 0.8$. Our goal is to extend the scope of the standard CC framework to photometric surveys. To achieve this, we first select a massive and passive galaxy sample using rest-frame colors and mass. Second, we design a Bayesian framework to infer full galaxy age posteriors in fine redshift bins, using a D4000-age-metallicity grid from stellar population synthesis (SPS) models. We also marginalize over metallicity, using a Gaussian metallicity prior to break the D4000-age-metallicity degeneracy. Subsequently, we derive age-difference posteriors between redshift bins by convolving their age posteriors to propagate the non-Gaussian features correctly. Finally, using the median and errors extracted from the differential age posteriors, we calculate the weighted average $H(z)$ over our selected redshift range. We obtain $H(z=0.65)=93.68\pm28.27\,{\rm (stat.)}\pm10.67\,{\rm (syst.)}\ {\rm km\,s^{-1}\,Mpc^{-1}}$, which is consistent with existing spectroscopic CC measurements and with the Planck $Λ$CDM prediction at the same redshift. This result provides a proof of concept for extending direct $H(z)$ measurements from cosmic chronometers to photometric and spectro-photometric surveys, where larger samples can compensate for lower spectral resolution, provided that passive-galaxy selection, metallicity priors, and stellar-population systematics are carefully controlled.

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arXiv2026

DeepDISC-Euclid: Source Classification and Photometric Redshifts in Euclid Deep Field North With a Pixel-Level Deep Learning Approach

The first Euclid Quick Data Release (Q1) provides extensive imaging and spectroscopic data for hundreds of millions of photometric objects across several deep fields. Accurate classifications and photometric redshifts (photo-z) for these sources are crucial to maximizing the value of these data. In this work, we perform source classification and photo-z estimation for the Euclid Deep Field North (EDF-N) around the North Ecliptic Pole, using a deep learning framework (DeepDISC) that learns and infers using 9-band images simultaneously. We train three dedicated models for (1) source detection and classification, (2) galaxy photo-z, and (3) quasar photo-z. The Euclid Q1 input source catalog, and classifications and spectroscopic redshifts (spec-z) from the Dark Energy Spectroscopic Instrument Data Release 1 are adopted as our training data. DeepDISC source detection achieves overall completeness of ~93% and purity of ~80% if using the Euclid source catalog as the ground truth. Using a JWST source catalog within EDF-N as the reference, we estimate a true purity of ~ 90% for DeepDISC sources. About 99.2%, 99.0%, and 84.8% of stars, galaxies, and quasars, respectively, are correctly recovered with their spectroscopic classifications. The DeepDISC photo-zs show good agreement with spectroscopic redshifts, for both galaxies and quasars. Comparisons with other Euclid Q1 products demonstrate that DeepDISC provides comparable or improved performance in source detection/deblending, classification and photo-z, especially for quasars. These results demonstrate the potential of pixel-level deep learning approaches for large-scale sky surveys such as Euclid and Roman, which will continue to improve with better training labels. We release the full DeepDISC source catalog (~13 million objects) for EDF-N with classifications and photo-zs, including photo-z probability distributions.

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arXiv2026

Extremely Metal-Poor Galaxies in DESI DR1: Connections to Galaxies in the Early Universe

Extremely Metal-Poor Galaxies (XMPGs), defined as having metallicities below 10\% of the solar value, are considered possible local analogs to primordial systems and offer a unique window into early galaxy evolution. This study presents a large-scale search for XMPGs using data from the Dark Energy Spectroscopic Instrument DR1, systematically evaluating their resemblance to high-redshift galaxies. From a parent sample of over 14 million galaxies, we identify 656 (551 new) confirmed XMPGs and 767 (670 new) high-quality candidates via the direct $T_{\mathrm{e}}$ method. Results reveal that XMPGs follow a distinct star-forming main sequence (SFMS) that is elevated and shallower than that of the comparing star-forming galaxies. Notably, at higher stellar masses ($M_{\star} > 10^{7.5} M_{\odot}$), the XMPG SFMS converges with the sequence observed in high-redshift galaxies by James Webb Space Telescope (JWST), indicating that mature XMPGs sustain star formation rates comparable to their primordial counterparts. Furthermore, XMPGs consistently deviate below the local fundamental metallicity relation, mirroring high-redshift galaxy behavior. These findings demonstrate that XMPGs not only exhibit low metallicities but also preserve scaling relations characteristic of the early Universe, confirming their potential value as local laboratories for studying early galaxy formation processes.

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arXiv2025

Deep Extragalactic VIsible Legacy Survey (DEVILS): Galaxy group catalogue for the D10-COSMOS field with 90% spectroscopic redshift completeness

Large-scale galaxy redshift surveys conducted over the last couple of decades have proven crucial in deepening our understanding of structure growth in the Universe and galaxy evolution. While there have been several such surveys, until now those that achieve the high completeness and precision necessary to probe the low-mass end of galaxy groups have been limited to relatively low redshifts ($z\lesssim0.3$), with surveys exploring the more distant Universe being constrained by small sample sizes and/or low redshift completeness. The recent Deep Extragalactic VIsible Legacy Survey (DEVILS) aims to explore galaxy environment over the last $\sim6$ Gyr with a completeness level comparable to the most complete local Universe surveys ($>85\%$). In this work, we present the galaxy group catalogue for the D10-COSMOS field from DEVILS, which achieves a redshift completeness of $90\%$ for galaxies with $Y<21.2$ mag. We showcase the science potential by exploring the impact of environment on the fraction and power of active galactic nuclei (AGN), finding that satellites in galaxy groups show no evidence of altered AGN properties, while satellites in clusters exhibit increased AGN fractions but decreased AGN luminosities.

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arXiv2025

Luminosity and stellar mass functions of faint photometric satellites around spectroscopic central galaxies from DESI Year-1 Bright Galaxy Survey

We measure the luminosity functions (LFs) and stellar mass functions (SMFs) of photometric satellite galaxies around spectroscopically identified isolated central galaxies (ICGs). The photometric satellites are from the DESI Legacy Imaging Surveys (DR9), while the spectroscopic ICGs are selected from the DESI Year-1 BGS sample. We can measure satellite LFs down to $r$-band absolute magnitudes of $M_{r,\mathrm{sat}}\sim-7$, around ICGs as small as $7.1<\log_{10}M_{\ast,\mathrm{ICG}}/\mathrm{M_\odot}<7.8$, with the stellar mass of ICGs measured by the DESI Fastspecfit pipeline. The satellite SMF can be measured down to $\log_{10}M_{\ast,\mathrm{sat}}/\mathrm{M_\odot}\sim 5.5$. Interestingly, we discover that the faint/low-mass end slopes of satellite LFs/SMFs become steeper with the decrease in the stellar masses of host ICGs, with smaller and nearby host ICGs capable of being used to probe their fainter satellites.. The steepest slopes are $-2.298\pm0.656$ and $-$2.888$\pm$0.916 for satellite LF and SMF, respectively. Detailed comparisons are performed between the satellite LFs around ICGs selected from DESI BGS or from the SDSS NYU-VAGC spectroscopic Main galaxies over $7.1<\log_{10}M_{\ast,\mathrm{ICG}}/\mathrm{M_\odot}<11.7$, showing reasonable agreements, but we show that the differences between DESI and SDSS stellar masses for ICGs play a role to affect the results. We also compare measurements based on DESI Fastspecfit and Cigale stellar masses used to bin ICGs, with the latter including the modeling of AGN based on WISE photometry, and we find good agreements in the measured satellite LFs by using either of the DESI stellar mass catalogs.

astro-ph.GA↗

arXiv2025

Deep Extragalactic VIsible Legacy Survey (DEVILS): New robust merger rates at intermediate redshifts

Mergers are fundamental to our understanding of the processes driving the evolution of the structure and morphology of galaxies, star formation, AGN activity, and the redistribution of stellar mass in the Universe. Determining the fraction and properties of mergers across cosmic time is critical to understanding the formation of the Universe we observe today. This fraction and its evolution also provide inputs and constraints for cosmological simulations, crucial for theoretical models of galaxy evolution. We present robust estimates of major close-pair fractions and merger rates at $0.2 < z < 0.9$ in the Deep Extragalactic VIsible Legacy Survey (DEVILS). We identify major mergers by selecting close-pairs with a projected spatial separation $r_{\mathrm{sep}} < 20$ h$^{-1}$ kpc and a radial velocity separation $v_{\mathrm{sep}} < 500$ km s$^{-1}$. For galaxies with stellar masses of log$_{10}$($M_\star$/$M_\odot$) = 10.66 $\pm$ 0.25 dex, we find a major close-pair fraction of $\approx 0.021$ at $0.2 < z < 0.34$ using a highly complete, unbiased spectroscopic sample. We extend these estimates to $0.2 < z < 0.9$ by combining the full probability distribution of redshifts for galaxies with high-quality spectroscopic, photometric, or grism measurements. Fitting a power-law $γ_{m} = A(1 + z)^m$, we find $A = 0.024 \pm 0.001$ and $m = 0.55 \pm 0.22$. Consistent with previous results, the shallow slope suggests weak redshift evolution in the merger fraction. When comparing with large hydrodynamical simulations, we also find consistent results. We convert close-pair fractions to merger rates using several literature prescriptions for merger timescales and provide all measurements for future studies.

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arXiv2024

Changing-look Active Galactic Nuclei from the Dark Energy Spectroscopic Instrument. II. Statistical Properties from the First Data Release

We present the identification of changing-look active galactic nuclei (CL-AGNs) from the Dark Energy Spectroscopic Instrument First Data Release and Sloan Digital Sky Survey Data Release 16 at z \leq 0.9. To confirm the CL-AGNs, we utilize spectral flux calibration assessment via an [O\,{\sc iii}]-based calibration, pseudo-photometry examination, and visual inspection. This rigorous selection process allows us to compile a statistical catalog of 561 CL-AGNs, encompassing 527 $\rm Hβ$, 149$\rm Hα$, and 129 Mg II CL behaviors. In this sample, we find 1) a 283:278 ratio of turn-on to turn-off CL-AGNs. 2) the critical value for CL events is confirmed around Eddington ratio \sim 0.01. 3) a strong correlation between the change in the luminosity of the broad emission lines (BEL) and variation in the continuum luminosity, with Mg II and $\rm Hβ$ displaying similar responses during CL phases. 4) the Baldwin-Phillips-Terlevich diagram for CL-AGNs shows no statistically difference from the general AGN catalog. 5) five CL-AGNs are associated with asymmetrical mid-infrared flares, possibly linked to tidal disruption events. Given the large CL-AGNs and the stochastic sampling of spectra, we propose that some CL events are inherently due to typical AGN variability during low accretion rates, particularly for CL events of the singular BEL. Finally, we introduce a Peculiar CL phase, characterized by a gradual decline over decades in the light curve and the complete disappearance of entire BEL in faint spectra, indicative of a real transition in the accretion disk.

astro-ph.GA↗

arXiv2024

DEVILS/MIGHTEE/GAMA/DINGO: The Impact of SFR Timescales on the SFR-Radio Luminosity Correlation

The tight relationship between infrared luminosity (L$_\mathrm{TIR}$) and 1.4 GHz radio continuum luminosity (L$_\mathrm{1.4GHz}$) has proven useful for understanding star formation free from dust obscuration. Infrared emission in star-forming galaxies typically arises from recently formed, dust-enshrouded stars, whereas radio synchrotron emission is expected from subsequent supernovae. By leveraging the wealth of ancillary far-ultraviolet - far-infrared photometry from the Deep Extragalactic VIsible Legacy Survey (DEVILS) and Galaxy and Mass Assembly (GAMA) surveys, combined with 1.4 GHz observations from the MeerKAT International GHz Tiered Extragalactic Exploration (MIGHTEE) survey and Deep Investigation of Neutral Gas Origins (DINGO) projects, we investigate the impact of timescale differences between far-ultraviolet - far-infrared and radio-derived star formation rate (SFR) tracers. We examine how the SED-derived star formation histories (SFH) of galaxies can be used to explain discrepancies in these SFR tracers, which are sensitive to different timescales. Galaxies exhibiting an increasing SFH have systematically higher L$_\mathrm{TIR}$ and SED-derived SFRs than predicted from their 1.4 GHz radio luminosity. This indicates that insufficient time has passed for subsequent supernovae-driven radio emission to accumulate. We show that backtracking the SFR(t) of galaxies along their SED-derived SFHs to a time several hundred megayears prior to their observed epoch will both linearise the SFR-L$_\mathrm{1.4GHz}$ relation and reduce the overall scatter. The minimum scatter in the SFR(t)-L$_\mathrm{1.4GHz}$ is reached at 200 - 300 Myr prior, consistent with theoretical predictions for the timescales required to disperse the cosmic ray electrons responsible for the synchrotron emission.

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arXiv2024

Overmassive black holes at cosmic noon: linking the local and the high-redshift Universe

We report for the first time a sample of 12 supermassive black holes (SMBHs) hosted by low-mass galaxies at cosmic noon, i.e., in a redshift range consistent with the peak of star formation history: $z \sim 1-3$. These black holes are two orders of magnitude too massive for the stellar content of their hosts when compared with the local relation for active galaxies. These overmassive systems at cosmic noon share similar properties with the high-$z$ sources found ubiquitously in recent \textit{James Webb Space Telescope} (\textit{JWST}) surveys (same range of black hole-to-stellar mass ratio, bolometric luminosity, and Eddington ratio). We argue that black hole feedback processes, for which there is possible evidence in five of the sources, and the differing environments in galactic nuclei at these respective epochs play a key role in these overmassive systems. These findings contribute to our understanding of the growth and co-evolution of SMBHs and their host galaxies across cosmic time, offering a link between the early Universe ($z > 4$) observed by \textit{JWST} and observations of the present-day Universe ($z \lesssim 1$).

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arXiv2023

A Large Sample of Extremely Metal-poor Galaxies at $z<1$ Identified from the DESI Early Data

Extremely metal-poor galaxies (XMPGs) at relatively low redshift are excellent laboratories for studying galaxy formation and evolution in the early universe. Much effort has been spent on identifying them from large-scale spectroscopic surveys or spectroscopic follow-up observations. Previous work has identified a few hundred XMPGs. In this work, we obtain a large sample of 223 XMPGs at $z<1$ from the early data of the Dark Energy Spectroscopic Instrument (DESI). The oxygen abundance is determined using the direct $T_{\rm e}$ method based on the detection of the [O III]$λ$4363 line. The sample includes 95 confirmed XMPGs based on the oxygen abundance uncertainty; remaining 128 galaxies are regarded as XMPG candidates. These XMPGs are only 0.01% of the total DESI observed galaxies. Their coordinates and other proprieties are provided in the paper. The most XMPG has an oxygen abundance of $\sim 1/34 Z_{\odot}$, stellar mass of about $1.5\times10^7 M_{\odot}$ and star formation rate of 0.22 $M_{\odot}$ yr$^{-1}$. The two most XMPGs present distinct morphologies suggesting different formation mechanisms. The local environmental investigation shows that XMPGs preferentially reside in relatively low-density regions. Many of them fall below the stellar mass-metallicity relations (MZRs) of normal star-forming galaxies. From a comparison of the MZR with theoretical simulations, it appears that XMPGs are good analogs to high-redshift star-forming galaxies. The nature of these XMPG populations will be further investigated in detail with larger and more complete samples from the on-going DESI survey.

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arXiv2023

GTC Follow-up Observations of Very Metal-Poor Star Candidates from DESI

The observations from the Dark Energy Spectroscopic Instrument (DESI) will significantly increase the numbers of known extremely metal-poor stars by a factor of ~ 10, improving the sample statistics to study the early chemical evolution of the Milky Way and the nature of the first stars. In this paper we report high signal-to-noise follow-up observations of 9 metal-poor stars identified during the DESI commissioning with the Optical System for Imaging and low-Intermediate-Resolution Integrated Spectroscopy (OSIRIS) instrument on the 10.4m Gran Telescopio Canarias (GTC). The analysis of the data using a well-vetted methodology confirms the quality of the DESI spectra and the performance of the pipelines developed for the data reduction and analysis of DESI data.

astro-ph.SR↗

arXiv2023

GAMA/DEVILS: Cosmic star formation and AGN activity over 12.5 billion years

We use the Galaxy and Mass Assembly (GAMA) and the Deep Extragalactic Visible Legacy Survey (DEVILS) observational data sets to calculate the cosmic star formation rate (SFR) and active galactic nuclei (AGN) bolometric luminosity history (CSFH/CAGNH) over the last 12.5 billion years. SFRs and AGN bolometric luminosities were derived using the spectral energy distribution fitting code ProSpect, which includes an AGN prescription to self consistently model the contribution from both AGN and stellar emission to the observed rest-frame ultra-violet to far-infrared photometry. We find that both the CSFH and CAGNH evolve similarly, rising in the early Universe up to a peak at look-back time $\approx 10$~Gyr ($z \approx 2$), before declining toward the present day. The key result of this work is that we find the ratio of CAGNH to CSFH has been flat ($\approx 10^{42.5}\mathrm{erg \, s^{-1}M_{\odot}^{-1}yr}$) for $11$~Gyr up to the present day, indicating that star formation and AGN activity have been coeval over this time period. We find that the stellar masses of the galaxies that contribute most to the CSFH and CAGNH are similar, implying a common cause, which is likely gas inflow. The depletion of the gas supply suppresses cosmic star formation and AGN activity equivalently to ensure that they have experienced similar declines over the last 10 Gyr. These results are an important milestone for reconciling the role of star formation and AGN activity in the life cycle of galaxies.

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arXiv2023

DESI Survey Validation Spectra Reveal an Increasing Fraction of Recently Quenched Galaxies at $z\sim1$

We utilize $\sim17000$ bright Luminous Red Galaxies (LRGs) from the novel Dark Energy Spectroscopic Instrument Survey Validation spectroscopic sample, leveraging its deep ($\sim2.5$ hour/galaxy exposure time) spectra to characterize the contribution of recently quenched galaxies to the massive galaxy population at $0.4 1$) of our sample of recently quenched galaxies represents the largest spectroscopic sample of post-starburst galaxies at that epoch. At $0.4 11.2$) LRGs by measuring the fraction of stellar mass each galaxy formed in the Gyr before observation, $f_\mathrm{1 Gyr}$. Although galaxies with $f_\mathrm{1 Gyr}>0.1$ are rare at $z\sim0.4$ ($\lesssim 0.5\%$ of the population), by $z\sim0.8$ they constitute $\sim3\%$ of massive galaxies. Relaxing this threshold, we find that galaxies with $f_\mathrm{1 Gyr}>5\%$ constitute $\sim10\%$ of the massive galaxy population at $z\sim0.8$. We also identify a small but significant sample of galaxies at $z=1.1-1.3$ that formed with $f_\mathrm{1 Gyr}>50\%$, implying that they may be analogues to high-redshift quiescent galaxies that formed on similar timescales. Future analysis of this unprecedented sample promises to illuminate the physical mechanisms that drive the quenching of massive galaxies after cosmic noon.

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arXiv2022

DEVILS: Cosmic evolution of SED-derived metallicities and their connection to star-formation histories

Gas-phase metallicities of galaxies are typically measured through auroral or nebular emission lines, but metallicity also leaves an imprint on the overall spectral energy distribution (SED) of a galaxy and can be estimated through SED fitting. We use the ProSpect SED fitting code with a flexible parametric star formation history and an evolving metallicity history to self-consistently measure metallicities, stellar mass, and other galaxy properties for $\sim90\,000$ galaxies from the Deep Extragalactic VIsible Legacy Survey (DEVILS) and Galaxy and Mass Assembly (GAMA) survey. We use these to trace the evolution of the mass-metallicity relation (MZR) and show that the MZR only evolves in normalisation by $\sim0.1\,$dex at stellar mass $M_\star = 10^{10.5}\,M_\odot$. We find no difference in the MZR between galaxies with and without SED evidence of active galactic nuclei emission at low redshifts ($z<0.3$). Our results suggest an anti-correlation between metallicity and star formation activity at fixed stellar mass for galaxies with $M_\star > 10^{10.5}\,M_\odot$ for $z<0.3$. Using the star formation histories extracted using ProSpect we explore higher-order correlations of the MZR with properties of the star formation history including age, width, and shape. We find that at a given stellar mass, galaxies with higher metallicities formed most of their mass over shorter timescales, and before their peak star formation rate. This work highlights the value of exploring the connection of a galaxy's current gas-phase metallicity to its star formation history in order to understand the physical processes shaping the MZR.

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