Aims. DustPedia and Local Volume Legacy (LVL) are two samples representative of the local galaxy population, including in total ∼1000 unique objects of all morphological types, with a wide range of stellar masses and star formation activity, and a spectral coverage from the ultraviolet to the far-infrared. The purpose of this work is to show that these samples cover two complementary ranges in stellar mass and galaxy morphology, making them an ideal set for constraining the dominant processes in the evolution of the galactic dust content. Methods. Using the multi-wavelength data provided by the two surveys, we fitted the galaxies’ spectral energy distribution and estimated their physical properties, in particular the stellar mass, M*, the specific dust mass, sMdust = Mdust/M*, and the specific star formation rate, sSFR = SFR/M*. Results. By combining DustPedia and LVL, we highlight that the trend of log10(sMdust) with log10(M*) is not monotonic. Thanks to a large number of objects across a wide range of M*, we have been able to fit two smoothly joined linear correlations: a positive one for log10(M*/M⊙)≲9.5 (a range populated mostly by LVL late spirals and irregulars), and a negative one for larger-mass, mainly DustPedia, spirals (with early-type galaxies being distinct and more dispersed in the same mass regime). For log10(M*/M⊙) > 9.5, we confirm a strong correlation between sMdust and sSFR; dwarf galaxies, instead, lie below this trend, showing a large scatter of sMdust for −10.5 < log10(sSFR/yr−1) < − 9.0. By using chemical evolution models we find that the observed log10(sMdust)–log10(M*) and log10(sMdust)–log10(sSFR) trends can be interpreted mainly by variations in the initial gas mass budget and the galaxy ages, respectively. Low-mass Sm-Irr galaxies with low sMdust and a high sSFR can only be reproduced by the models by assuming a highly efficient photofragmentation rate of large grains, and/or low grain growth in clouds.

We analysed the stellar population properties of a well-defined sample of 552 galaxies at redshift 0.6 < z < 0.77 drawn from the LEGA-C spectroscopic survey. This paper is the first of a series, and it is aimed at (i) presenting the catalogue of revised absorption indices for LEGA-C DR3 and of the inferred physical parameter estimates while describing their systematic uncertainties and at (ii) deriving benchmark scaling relations for the general massive galaxy population at intermediate redshift. We estimated light-weighted mean ages and stellar metallicities through careful analysis of key absorption features in the stellar continuum spectra of the galaxies coupled with photometry. The observables were interpreted in a Bayesian framework with a comprehensive library of model spectra based on stochastic star formation histories, chemical enrichment histories, and dust attenuations. We discuss various sources of systematic uncertainties within our method as well as systematic differences with results from other spectral fitting approaches. We derived volume-weighted scaling relations connecting light-weighted mean ages and stellar metallicities with galaxy stellar mass for the general galaxy population at < z > = 0.7 and masses > 10(10) M-circle dot. We find the downsizing trends observed in the local Universe to be already in place 6 Gyr ago. We also observe a bimodal distribution of light-weighted ages as a function of mass, transitioning around 10(11) M-circle dot. Such a bimodality is not observed in the stellar metallicity-mass relation, which changes from a steep to a flat regime across M-* similar to 10(10.8) M-circle dot. Similar trends in age and metallicity also emerge as a function of velocity dispersion, but with a sharper transition from young to old around log sigma(*) = 2.3. Differences with respect to the trends as a function of stellar mass suggest that age is primarily dependent on velocity dispersion below and above the transition regime, while both the stellar mass and the depth of the total gravitational potential well (as traced by the velocity dispersion) contribute to stellar metallicity. We release the catalogues of revised absorption index measurements for LEGA-C DR3 used in this work and of the inferred stellar population physical parameters to public repositories.

DustPedia and LVL are two samples representative of the local galaxy population, including in total 1011 unique objects of all morphological types, with a wide range of stellar masses (M_*) and star-formation activity, and a spectral coverage from the FUV to the FIR. The purpose of this work is to show that these samples cover two complementary ranges in M_* and morphology, making them an ideal set for constraining the dominant processes in the evolution of the galactic dust content. Using the multiwavelength data provided by the two surveys, we fitted the galaxies' spectral energy distribution and estimated their physical properties, in particular the M_*, sM_dust=M_dust/M_*, and sSFR = SFR/M_*. By combining DustPedia and LVL, we highlight that the log_10(sM_ dust)-log_10(M_*) trend is not monotonic. Thanks to a large number of objects across a wide range of M_*, we have been able to fit two smoothly-joined linear correlations: a positive for log_10(M_*/M_⊙)≲9.5 (mainly LVL late spirals and irregulars), and a negative one for larger-mass, mainly DustPedia spirals (early types are distinct and more dispersed in the same mass regime). For log_10(M_*/M_⊙)>9.5, we confirm a strong sM_dust-sSFR correlation; dwarf galaxies, instead, lie below this trend, with a large scatter of sM_ dust, for -10.5<log_10(sSFR/yr^-1)<-9.0. By using chemical evolution models we find that the observed log_10(sM_ dust)-log_10(M_*) and log_10(sM_ dust)-log_10(sSFR) trends can be interpreted mainly by variations in the initial gas mass budget and the galaxy ages, respectively. Low-mass Sm-Irr galaxies with low sM_ dust and high sSFR can only be reproduced by the models by assuming high photofragmentation rate of large grains, and/or low grain-growth in clouds.

The background galaxies in Euclid Early Release Observation images of the Perseus cluster make up a remarkable sample for the combination of a 0.57 deg2 area, 25.3 and 23.2 AB mag depth, and angular resolutions in the optical and near-infrared bands of 0⋅′′1 and 0⋅′′3, respectively. As part of the effort towards characterising the history of the Hubble sequence, we performed a morphological analysis of 2445 and 12 786 galaxies with IE ≤ 21 and IE ≤ 23, respectively. We used single-Sérsic profiles and the sums of a Sérsic bulge and an exponential disc to model these galaxies with SourceXtractor++ and analysed their positional, structural, and flux parameters in order to assess their similarities and differences. The fitted galaxies to IE ≤ 21 span the various Hubble types with ubiquitous bulge and disc components and a bulge-to-total light ratio (B/T) that takes all values from 0 to 1. The effective radius of the single-Sérsic profile is an intermediate estimate of galaxy size (between the bulge and disc effective radii) depending on B/T. The axis ratio of the single-Sérsic profile is higher than the disc axis ratio, and this difference increases with B/T. The choice of model impacts the photometry with −0.08 to 0.01 mag median systematic IE offsets between single-Sérsic and bulge-disc total magnitudes and a 0.05–0.15 mag dispersion from low to high B/T. We measured a median 0.3 mag bulge-disc colour difference in rest-frame Mg − Mi that originates from the disc-dominated galaxies, whereas bulge-dominated galaxies have median colours similar to those of their components. Remarkably, we also measured redder inside disc colour gradients based on 5 to 10% systematic variations of disc effective radii between the optical and near-infrared bands. This analysis demonstrates the usefulness and limitations of single-Sérsic profile modelling and the power of bulge-disc decomposition for characterising the morphology of lenticulars and spirals in Euclid images. We make available the catalogues of best-fit parameters for the morphological and SED fits.

We present the second data release (DR2) of the TNG50-SKIRT Atlas (TSA), a library of synthetic, spatially resolved galaxy observables. The atlas is constructed by post-processing a stellar-mass-complete (10^9.8 M_⊙ < M_⋆ < 10^12 M_⊙) sample of 1154 z=0 galaxies from the TNG50 cosmological hydrodynamical simulation with the Monte Carlo radiative transfer code SKIRT. Compared to the first release, TSA DR2 extends the wavelength coverage from the ultraviolet to the submillimetre, including dust emission, and incorporates updated stellar population models together with an improved treatment of dust-enshrouded star-forming regions. The atlas provides spatially resolved spectral energy distributions, broadband images, and physical property maps for multiple viewing orientations, as well as a catalogue of integrated properties enabling direct comparison with unresolved observations. We validate the data products through extensive quality control, including an assessment of Monte Carlo noise, and demonstrate their internal consistency using diagnostic relations between luminosities and star formation rates. TSA DR2 provides a versatile resource for studies of dust attenuation and emission, star formation tracers, galaxy morphology, and multi-wavelength scaling relations across spatial scales. The atlas and associated data products are publicly released and are intended to support a wide range of observationally oriented studies of galaxy evolution.

We analysed the stellar population properties of a well-defined sample of 552 galaxies at redshift 0.6 < z < 0.77 drawn from the LEGA-C spectroscopic survey. This paper is the first of a series, and it is aimed at (i) presenting the catalogue of revised absorption indices for LEGA-C DR3 and of the inferred physical parameter estimates while describing their systematic uncertainties and at (ii) deriving benchmark scaling relations for the general massive galaxy population at intermediate redshift. We estimated light-weighted mean ages and stellar metallicities through careful analysis of key absorption features in the stellar continuum spectra of the galaxies coupled with photometry. The observables were interpreted in a Bayesian framework with a comprehensive library of model spectra based on stochastic star formation histories, chemical enrichment histories, and dust attenuations. We discuss various sources of systematic uncertainties within our method as well as systematic differences with results from other spectral fitting approaches. We derived volume-weighted scaling relations connecting light-weighted mean ages and stellar metallicities with galaxy stellar mass for the general galaxy population at ⟨z⟩ = 0.7 and masses > 1010 M⊙. We find the downsizing trends observed in the local Universe to be already in place 6 Gyr ago. We also observe a bimodal distribution of light-weighted ages as a function of mass, transitioning around 1011 M⊙. Such a bimodality is not observed in the stellar metallicity-mass relation, which changes from a steep to a flat regime across M* ∼ 1010.8 M⊙. Similar trends in age and metallicity also emerge as a function of velocity dispersion, but with a sharper transition from young to old around log σ* = 2.3. Differences with respect to the trends as a function of stellar mass suggest that age is primarily dependent on velocity dispersion below and above the transition regime, while both the stellar mass and the depth of the total gravitational potential well (as traced by the velocity dispersion) contribute to stellar metallicity. We release the catalogues of revised absorption index measurements for LEGA-C DR3 used in this work and of the inferred stellar population physical parameters to public repositories.

We analysed a sample of 552 galaxies from the LEGA-C spectroscopic survey (0.6 < z < 0.77), for which we estimated the stellar population parameters by a Bayesian analysis of the stellar absorption features and photometry. We investigated the effect of the current star formation activity on light-weighted mean stellar ages and metallicities and their median trends with stellar mass or velocity dispersion. The bimodality in the global age-mass relation stems from the different age distributions in the quiescent and star-forming populations. No bimodality is observed in the stellar metallicity-mass relation, although quiescent and star-forming galaxies have different distributions in this parameter space. We identified a high-metallicity sequence populated by quiescent and weakly star-forming galaxies. At masses lower than 10(10.8) M-circle dot, the median stellar metallicity-mass relation of star-forming galaxies steepens as a consequence of the increasing scatter towards lower stellar metallicities for galaxies with an increasing specific star formation rate at fixed mass. Relying on a consistent analysis of SDSS DR7 spectra and accounting for aperture corrections, we quantified the evolution of the volume-weighted stellar age and stellar metallicity scaling relations between z = 0.7 and the present. We found negligible evolution in the stellar metallicity-mass relation of quiescent galaxies and for M-* > 10(11) M-circle dot galaxies in general. Lower-mass star-forming galaxies instead have typically lower metallicities than their local counterparts, indicating significant enrichment since z similar to 0.7 in the low-mass regime. Notably, the median of the stellar ages of the general population and of quiescent galaxies has changed by only 2 Gyr between z = 0.7 and z = 0.1, which is less than expected from cosmic ageing. Some quiescent galaxies must evolve passively to reach the old boundary of the local population. In order to explain the evolution of the median trends, however, both individual evolution through rejuvenation and/or minor merging that affects the outer galaxy regions and population evolution through quenching of massive metal-rich star-forming galaxies are required.

Aims. We analyzed the sizes and star formation histories (SFHs) of 2908 galaxies with M ★ ≥ 10 9 M ⊙ at 0.6 < z < 1.0, drawn from the Large Early Galaxy Astrophysics Census (LEGA-C) survey. The goal is to investigate the connection between galaxy sizes with SFH, stellar age, and metallicity. Methods. The SFHs were derived with Prospector by fitting the high signal-to-noise ratio, high spectral resolution spectroscopy drawn from the LEGA-C DR3 together with the broadband photometry from the UltraVISTA catalog. The galaxy sizes were measured by fitting a 2D Sérsic profile to the HST ACS F814W images. Results. We find diverse SFHs and quenching timescales ( τ q ). The main quiescent population quenched over τ q = 1.23 ± 0.04 Gyr, whereas the compact post-starburst galaxies (PSBs) quenched much faster, τ q = 0.13 ± 0.03 Gyr. At fixed stellar mass, smaller quiescent galaxies quenched more rapidly than larger ones; at fixed size, the dependence on stellar mass is weak. Larger quiescent galaxies are marginally younger, quenched more slowly, and have near-solar metallicities, while compact quiescent galaxies are older, metal-rich, and quenched faster. PSBs formed half their mass later ( z form ∼ 1.9) and quenched on the shortest timescales. The general trends with galaxy size, Z ★ , and z form for the quiescent populations remain consistent regardless of the method used to derive the stellar properties. Conclusions. We conclude that compact quiescent galaxies are consistent with both early moderately fast quenching and with more rapid late quenching. While this may suggest the existence of multiple quenching channels, our data are also compatible with a continuous distribution of quenching timescales. These findings suggest that different physical mechanisms may drive quenching across galaxy populations, potentially leading to similar morphological outcomes despite the differing evolutionary histories.

Aims. We investigate the impacts of the evolution of dust mass and grain size distribution on the evolution of global attenuation curves, with a focus on the optical-ultraviolet (UV) slope and the 2175 Å bump, within a Milky Way-like (MW-like) galaxy simulation. In addition, we discuss the contributions of the star-dust geometry, scattering, and dust properties to the attenuation curves. Methods. We performed the post-processing dust radiative transfer using the SKIRT code based on a MW-like galaxy simulation. The hydrodynamic simulation was carried out with the GADGET4-OSAKA code, which models the evolution of grain size distributions. Results. For lower inclination angles (i.e., closer to face-on), the attenuation curve flattens over time up to t = 1 Gyr and becomes progressively steeper. The steeper slope of the attenuation curve is caused by the interplay between scattering and the dust disk becoming more extended over time (i.e., changes in the star-dust geometry). At higher inclination angles, the effect of scattering is suppressed and the attenuation curves steepen slightly over time due to the formation of small grains and the bias of observed UV emission toward old stars. The 2175 Å bump becomes stronger on a timescale of ∼250 Myr due to the formation of small carbonaceous grains. However, the bump strength is affected not only by the abundance of small grains, but also by star-dust geometry. At higher AV, or at higher inclination angles, the bump strengths become weaker. These results may help interpret flatter attenuation curves and less prominent bumps in high-redshift galaxies. Furthermore, we find that variations in the star-dust geometry alter the amount of scattered photons escaping the galaxy, thereby driving the anti-correlation between the slope and V-band attenuation, AV. The scatter in this relation arises from differences in dust optical depth along and perpendicular to the line of sight, reflecting differences in the inclination and star-dust geometry. Additional contributions to the scatter come from variations in the grain size distribution and the fraction of obscured young stars.

Context: Galaxy morphology is a fundamental property to describe galaxy evolution. However, the observed morphology of a particular galaxy may depend on the observed wavelength. Aims: Our aim is to investigate the wavelength dependence and the effect of dust attenuation on nonparametric morphology indicators. Methods: We use the TNG50-SKIRT Atlas, an atlas of synthetic UV to near-infrared (NIR) broadband images for a complete stellar-mass-selected sample of 1154 galaxies extracted from the TNG50 cosmological simulation at z = 0. For each image, we calculate four nonparametric morphology indicators using the StatMorph code. Results: We find that the known correlations between the stellar mass and the morphological parameters measured in the optical, together with the Gini-M_20, concentration-Gini, and concentration-M_20 planes, are fully consistent with observational data. However, nonparametric morphological indicators change significantly with wavelength and that this wavelength dependence is stronger for disc-dominated than for bulge-dominated galaxies. The wavelength dependence of the morphology of our simulated TNG50 galaxies is consistent with measurements of local galaxies from the SINGS survey. We demonstrate that the effect of dust attenuation on nonparametric morphology indicators is modest across the full galaxy population but can be significant for individual galaxies.

The James Webb Space Telescope (JWST) is unveiling the rest-frame near-IR structure of galaxies. We measure the evolution with redshift of the rest-frame optical and near-IR Sérsic index (n), and examine the dependence on stellar mass and star-formation activity across the redshift range 0.5≤ z≤2.5. We infer rest-frame near-IR Sérsic profiles for ≈ 15.000 galaxies in publicly available NIRCam imaging mosaics from the COSMOS-Web and PRIMER surveys. We augment these with rest-frame optical Sérsic indices, previously measured from HST imaging mosaics. The median Sérsic index evolves slowly or not at all with redshift, except for very high-mass galaxies (M_⋆ > 10^11 M_⊙), which show an increase from n≈ 2.5 to n≈ 4 at z<1. High-mass galaxies have higher n than lower-mass galaxies (M_⋆=10^9.5 M_⊙) at all redshifts, with a stronger dependence in the rest-frame near-IR than in the rest-frame optical at z>1. This wavelength dependence is caused by star-forming galaxies that have lower optical than near-IR n at z>1 (but not at z<1). Both at optical and near-IR wavelengths, star-forming galaxies have lower n than quiescent galaxies, fortifying the connection between star-formation activity and radial stellar mass distribution. At z>1 the median near-IR n varies strongly with star formation activity, but not with stellar mass. The scatter in near-IR n is higher in the green valley (0.25 dex) than on the star-forming sequence and among quiescent galaxies (0.18 dex) – this trend is not seen in the optical because dust and young stars contribute to the variety in optical light profiles. Our newly measured rest-frame near-IR radial light profiles motivate future comparisons with radial stellar mass profiles of simulated galaxies as a stringent constraint on processes that govern galaxy formation.

The properties of interstellar dust grains are being scrutinized more than ever before, with the advent of large facilities. Infrared emission from dust grains is a powerful asset that can help constrain their physical and chemical properties. Among these, the relative ratio of carbon-rich to silicate-rich grains remains one that has not yet been investigated thoroughly due to the lack of dedicated instruments and modeling limitations. We quantify the modeling degeneracies inherent to constraining the far-infrared (far-IR) slope of the dust emission spectral energy distribution. Used as a proxy for the silicate-to-carbon ratio, we find that recovering the far-IR slope is affected by the estimate of the local radiation field and the input abundances of different grain species. We show that PRIMA's hyperspectral imaging will lead to better constrained local radiation fields, which will aid-together with PRIMA's polarization capabilities-to better constrain the silicate-to-carbon ratio in M31, and how it spatially varies within the galaxy. (c) The Authors. Published by SPIE under a Creative Commons Attribution 4.0 International License. Distribution or reproduction of this work in whole or in part requires full attribution of the original publication, including its DOI. [DOI: 10.1117/1.JATIS.11.3.031623]

Context. As a major cooling line of interstellar gas, the far-infrared 158 mu m line from singly ionised carbon [C II] is an important tracer of various components of the interstellar medium in galaxies across all spatial and morphological scales. Yet, there is still not a strong constraint on the origins of [C II] emission. Aims. In this work, we derive the resolved [C II] star formation rate relation and aim to unravel the complexity of the origin of [C II]. Methods. We used the Field-Imaging Far-Infrared Line Spectrometer on board the Stratospheric Observatory for Infrared Astronomy to map [C II] in three nearby star-forming galaxies at sub-kiloparsec scales, namely, NGC 3627, NGC 4321, and NGC 6946, and we compared these [C II] observations to the galactic properties derived from complementary data from the literature. Results. We find that the relationship between the [C II] fine structure line and star formation rate shows variations between the galaxies as well as between different environments within each galaxy. Conclusions. Our results show that the use of [C II] as a tracer for star formation is much more tangled than has previously been suggested within the extragalactic literature, which typically focuses on small regions of galaxies and/or uses large-aperture sampling of many different physical environments. As found within resolved observations of the Milky Way, the picture obtained from [C II] observations is complicated by its local interstellar medium conditions. Future studies will require a larger sample and additional observational tracers, obtained on spatial scales within galaxies, in order to accurately disentangle the origin of [C II] and calibrate its use as a star formation tracer.

With a sample of 552 galaxies at z 0.7 from the LEGA-C survey, we investigate how current star formation influences light-weighted mean stellar ages and metallicities, and their median trends with stellar mass or velocity dispersion. The bimodality in the global age-mass relation stems from the different age distributions in the quiescent (Q) and star-forming (SF) populations. A bimodality is not observed in the stellar metallicity-mass relation, although Q and SF galaxies have different distributions in this parameter space. We identify a high-metallicity sequence populated by both Q and weakly SF galaxies. At masses below logM/Msun=10.8 the median stellar metallicity-mass relation of SF galaxies steepens, as a consequence of increasing scatter toward lower stellar metallicities for galaxies with increasing specific star formation rate at fixed mass. With a consistent analysis of SDSS DR7 spectra, accounting for aperture corrections, we quantify the evolution of the stellar age and stellar metallicity scaling relations between z=0.7 and the present. We find negligible evolution in the stellar metallicity-mass relation of Q galaxies and for logM/Msun>11 galaxies in general. Lower mass SF galaxies, instead, have typically lower metallicities than their local counterparts, indicating significant enrichment since z 0.7 in the low-mass regime. The median of the stellar ages of both the general population and Q galaxies has changed by only 2 Gyr between z=0.7 and z=0.1, less than expected from cosmic aging. Some Q galaxies must evolve passively to reach the old boundary of the local population. However, in order to explain the evolution of the median trends, both individual evolution, through rejuvenation and/or minor merging impacting the outer galaxy regions, and population evolution, through quenching of massive, metal-rich star-forming galaxies, are required. (Abridged)

The Euclid mission is generating a vast amount of imaging data in four broadband filters at a high angular resolution. This data will allow for the detailed study of mass, metallicity, and stellar populations across galaxies that will constrain their formation and evolutionary pathways. Transforming the Euclid imaging for large samples of galaxies into maps of physical parameters in an efficient and reliable manner is an outstanding challenge. Here, we investigate the power and reliability of machine learning techniques to extract the distribution of physical parameters within well-resolved galaxies. We focus on estimating stellar mass surface density, mass-averaged stellar metallicity, and age. We generated noise-free synthetic high-resolution (100 pcx100 pc) imaging data in the Euclid photometric bands for a set of 1154 galaxies from the TNG50 cosmological simulation. The images were generated with the SKIRT radiative transfer code, taking into account the complex 3D distribution of stellar populations and interstellar dust attenuation. We used a machine learning framework to map the idealised mock observational data to the physical parameters on a pixel-by-pixel basis. We find that stellar mass surface density can be accurately recovered with a <= 0.130 dex scatter. Conversely, stellar metallicity and age estimates are, as expected, less robust, but they still contain significant information that originates from underlying correlations at a sub-kiloparsec scales between stellar mass surface density and stellar population properties. As a corollary, we show that TNG50 follows a spatially resolved mass-metallicity relation that is consistent with observations. Due to its relatively low computational and time requirements, which has a time-frame of minutes without dedicated high performance computing infrastructure once it has been trained, our method allows for fast and robust estimates of the stellar mass surface density distributions of nearby galaxies from four-filter Euclid imaging data. Equivalent estimates of stellar population properties (stellar metallicity and age) are less robust but still hold value as first-order approximations across large samples.

We present the redshift evolution of radial color gradients (in rest-frame U - V and V - J) for galaxies in the range 0.5< z <2.5 and investigate their origin and dependence on stellar mass. We select ∼ 10,200 galaxies with stellar masses M_⋆>10^9.5 M_⊙ from publicly available JWST/NIRCam-selected catalogs. Using 2D Sérsic profile fits to account for PSF broadening, we perform spatially resolved SED fitting on HST and JWST/NIRCam photometry retrieving accurate rest-frame U - V and V - J color gradients within 2R_e, F444W. Star-forming galaxies generally exhibit negative V - J color gradients that are strongly mass and redshift dependent. For massive star-forming galaxies (M_⋆>10^10.5 M_⊙) at z>1.5 V - J colors are ≈ 0.5 mag redder within the effective radius than outside, on average. We find that, at all redshifts and across the entire stellar mass range, V - J gradients strongly correlate with global attenuation (A_V), suggesting that they predominantly trace dust attenuation gradients. Edge-on galaxies are redder and have stronger gradients at all z, although the correlation weakens at higher z. The U - V and V - J color gradients in the quiescent galaxy population, in contrast, are weakly negative (from ≈ -0.1 to ≈- 0.2 mag), though significant, and show little or no dependence on stellar mass, redshift or axis ratio. The implication is that quiescent galaxies must be largely transparent, with low A_V, and color gradients mostly attributable to stellar population gradients.

We investigate the impacts of the evolution of dust mass and grain size distribution within a Milky Way-like (MW-like) galaxy simulation on global attenuation curves, focusing on the optical-UV slope and the 2175 AA bump. We discuss the contributions of star-dust geometry, scattering, and dust properties. Post-processing dust radiative transfer was performed using SKIRT based on the MW-like galaxy simulation. The simulation was carried out with GADGET4-OSAKA, which models the evolution of grain size distributions. For lower inclination angles (closer to face-on), the attenuation curve flattens over time up to t=1 Gyr, then becomes progressively steeper. This steeper slope arises from the interplay between scattering and the dust disk becoming more extended over time (changes in star-dust geometry). At higher inclination, scattering is suppressed, and the attenuation curves slightly steepen over time due to small-grain formation and the bias of observed UV light toward older stars. The bump strengthens on a timescale of 250 Myr due to the formation of small carbonaceous grains. The bump strength is affected not only by the abundance of small grains but also by star-dust geometry. At higher A_V or higher inclination, the bump weakens. These results may help interpret flatter attenuation curves and weaker bumps in high-redshift galaxies. Variations in star-dust geometry alter the amount of scattered photons escaping the galaxy, driving the anti-correlation between the slope and A_V. Scatter in this relation arises from differences in dust optical depth along and perpendicular to the line of sight, reflecting inclination and star-dust geometry. Additional contributions come from variations in grain size distribution and the fraction of obscured young stars.

The Euclid ERO programme targeted the Perseus cluster of galaxies, gathering deep data in the central region of the cluster over 0.7 square degree, corresponding to approximately 0.25 r_200. The data set reaches a point-source depth of IE=28.0 (YE, JE, HE = 25.3) AB magnitudes at 5 sigma with a 0.16" and 0.48" FWHM, and a surface brightness limit of 30.1 (29.2) mag per square arcsec. The exceptional depth and spatial resolution of this wide-field multi-band data enable the simultaneous detection and characterisation of both bright and low surface brightness galaxies, along with their globular cluster systems, from the optical to the NIR. This study advances beyond previous analyses of the cluster and enables a range of scientific investigations summarised here. We derive the luminosity and stellar mass functions (LF and SMF) of the Perseus cluster in the Euclid IE band, thanks to supplementary u,g,r,i,z and Halpha data from the CFHT. We adopt a catalogue of 1100 dwarf galaxies, detailed in the corresponding ERO paper. We identify all other sources in the Euclid images and obtain accurate photometric measurements using AutoProf or AstroPhot for 138 bright cluster galaxies, and SourceExtractor for half a million compact sources. Cluster membership for the bright sample is determined by calculating photometric redshifts with Phosphoros. Our LF and SMF are the deepest recorded for the Perseus cluster, highlighting the groundbreaking capabilities of the Euclid telescope. Both the LF and SMF fit a Schechter plus Gaussian model. The LF features a dip at M(IE)=-19 and a faint-end slope of alpha_S = -1.2 to -1.3. The SMF displays a low-mass-end slope of alpha_S = -1.2 to -1.35. These observed slopes are flatter than those predicted for dark matter halos in cosmological simulations, offering significant insights for models of galaxy formation and evolution.

We present the stellar properties of 2908 galaxies at 0.6 < z < 1.0 from the LEGA-C survey. We emphasize the importance of high signal-to-noise, high spectral resolution spectroscopy in the inference of stellar population properties of galaxies. We estimate the galaxy properties with the SED fitting code Prospector, by fitting spectroscopy and broadband photometry together, drawn from the LEGA-C DR3 and UltraVISTA catalogs respectively. We report a positive correlation between light-weighted ages and stellar velocity dispersion (σ_⋆). The trend with σ_⋆ is weaker for the mass-weighted ages and stellar metallicity (Z_⋆). On average, quiescent galaxies are characterized by high Z_⋆, they are ∼1.1 Gyr older, less dusty, with steeper dust attenuation slopes compared to star-forming galaxies. Conversely, star-forming galaxies are characterized by significantly higher dust optical depths and shallower (grayer) attenuation slopes. Low mass (high mass) star-forming galaxies have lower (higher) Z_⋆, while their stellar populations are on average younger (older). A key pragmatic result of our study is that a linear-space metallicity prior is preferable to a logarithmic-space one when using photometry alone, as the latter biases the posteriors downward. Spectroscopy greatly improves stellar population measurements and is required to provide meaningful constraints on age, metallicity, and other properties. Pairing spectroscopy with photometry helps resolving the dust-age-metallicity degeneracy, yielding more accurate mass- and light-weighted ages, with ages inferred from photometry alone suffering such large uncertainties. Stellar metallicities are constrained by our spectroscopy, but precise measurements remain challenging (and impossible with photometry alone), particularly in the absence of Mg and Fe lines redward of 5000 Å in the observed spectrum.

We analyze stellar population properties of 552 galaxies at redshift 0.6=0.7 and masses >10^10Msun. The downsizing trends observed locally were already in place 6 Gyr ago. We observe bimodal age distribution as a function of mass, transitioning around 10^11Msun. No bimodality appears in the stellar metallicity-mass relation, which changes from steep to flat across 10^10.8Msun. Similar trends emerge for age and metallicity with velocity dispersion, but with sharper transition from young to old around log(sigma)=2.3. Differences with respect to trens with stellar mass suggest that age primarily depends on velocity dispersion below and above the transition regime, while both stellar mass and velocity dispersion contribute to stellar metallicity. The catalogs of revised absorption index measurements for LEGA-C DR3 and inferred stellar population physical parameters will be released to public repositories. (Abridged)