arXiv subjects

I. Ferreras

Publications and source records attributed to I. Ferreras.

At least 19 recordsLinked to original sources

arXiv2026

Different paths, same appearance: an intermediate-age red nugget at z~0.13

Massive ultra-compact galaxies are commonly regarded as nearby relics of the compact quiescent population at z~2-3, and detailed studies have focused so far only on old systems in dense environments. Here we present a spatially resolved analysis of G79071, an ultra-compact (R_e<2kpc), massive (M*~10^{11}MSun) ETG at z~0.13 residing in a low-mass group environment, based on deep VLT/X-Shooter long-slit spectroscopy. We extract stellar kinematics out to ~4R_e and constrain stellar population properties and the low-mass end of the stellar IMF, by combining full spectral fitting, full-index fitting, and index fitting, using different stellar population models. G79071 shows significant rotation, consistent with a fast-rotator-like kinematic structure, and is dominated by an intermediate-age stellar population (~3-4Gyr) with a flat age profile and no evidence for a significantly old (>5Gyr) component. The central metallicity is supersolar and decreases with radius, while most abundance ratios show flat radial trends and are consistent with typical massive, low-redshift ETGs at similar velocity dispersion. Moreover, metallicity and [Na/Fe] abundance are significantly enhanced, reflecting a very efficient chemical enrichment process.Our analysis suggests that the IMF remains bottom-heavy out to ~2R_e, implying a mass-excess factor alpha>~2. Jeans anisotropic models with an NFW halo are consistent with the IMF-based stellar mass normalization and with compactness-corrected (non-homologous) dynamical mass estimators, yielding a modest projected dark-matter fraction within one effective radius, f_DM(<R_e)=0.18 \pm 0.07. These results show that at least some massive compact galaxies with a bottom-heavy IMF can form and persist at lower redshift and outside high-density environments, providing new constraints on the diversity of formation pathways for massive galaxies.

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arXiv2025

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

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

astro-ph.IM↗

arXiv2025

Evaluating quenching in cosmological simulations of galaxy formation with spectral covariance in the optical window

Cosmological hydrodynamical simulations provide valuable insights on galaxy evolution when coupled with observational data. Comparisons with real galaxies are typically performed via scaling relations of the observables. Here we follow an alternative approach based on the spectral covariance in a model-independent way. We build upon previous work by Sharbaf et al. that studied the covariance of high quality SDSS continuum-subtracted spectra in a relatively narrow range of velocity dispersion ($σ\in [100,150]$\,km\,s$^{-1}$). Here the same analysis is applied to synthetic data from the EAGLE and Illustris TNG100 simulations, to assess the ability of these runs to mimic real galaxies. The real and simulated spectra are consistent regarding spectral covariance, although with subtle differences that can inform the implementation of subgrid physics. Spectral fitting done a posteriori on stacks segregated with respect to latent space reveals that the first principal component (PC1) is predominantly influenced by the stellar age distribution, with an underlying age-metallicity degeneracy. Good agreement is found regarding star formation prescriptions but there is disagreement with AGN feedback, that also affects the subset of quiescent galaxies. We show a substantial difference in the implementation of the AGN subgrid prescriptions, regarding central black hole seeding, that could lead to the mismatch. Differences are manifest between these two simulations in the star formation histories stacked with respect to latent space. We emphasise that this methodology only relies on the spectral covariance to assess whether simulations provide a true representation of galaxy formation.

astro-ph.CO↗

arXiv2024

On the Dust properties of the UV galaxies in the redshift range $z \sim 0.6-1.2$

Far-infrared observations from the \textit{Herschel Space Observatory} are used to estimate the infrared (IR) properties of ultraviolet-selected galaxies. We stack the PACS (100, 160 $μ\mathrm{m}$) and SPIRE (250, 350 and 500$μ\mathrm{m}$) maps of the Chandra deep field south (CDFS) on a source list of galaxies selected in the rest-frame ultraviolet (UV) in a redshift range of $0.6-1.2$. This source list is created using observations from the XMM-OM telescope survey in the CDFS using the UVW1 (2910 Å) filter. The stacked data are binned according to the UV luminosity function of these sources, and the average photometry of the UV-selected galaxies is estimated. By fitting modified black bodies and IR model templates to the stacked photometry, average dust temperatures and total IR luminosity are determined. The luminosity-weighted average temperatures are consistent with a weak trend of increasing temperature with redshift found by previous studies. Infrared excess, unobscured, and obscured star formation rate (SFR) values are obtained from the UV and IR luminosities. We see a trend in which dust attenuation increases as UV luminosity decreases. It remains constant as a function of IR luminosities at fixed redshift across the luminosity range of our sources. In comparison to local luminous infrared galaxies with similar SFRs, the higher redshift star-forming galaxies in the sample show a lesser degree of dust attenuation. Finally, the inferred dust attenuation is used to correct the unobscured SFR density in the redshift range $0.6-1.2$. The dust-corrected SFR density is consistent with measurements from IR-selected samples at similar redshifts.

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arXiv2024

Exploring Galaxy Evolution Time-Scales in Clusters: Insights from the Projected Phase Space

Galaxies infalling into clusters undergo both star-formation quenching and morphological transformation due to environmental effects. We investigate these processes and their timescales using a local sample of 20,191 cluster and 11,674 field galaxies from SDSS. By analysing morphology as a function of distance from the star-formation main sequence, we show that environmental influence is especially pronounced for low-mass galaxies, which emerge from the green valley with early-type morphologies before their star formation is fully suppressed. Using the galaxies' positions in the clusters' Projected Phase Space, we examine the evolution of blue cloud, green valley, and red sequence fractions as a function of time since infall. Interestingly, the green valley fraction remains constant with time since infall, suggesting a balanced flow of galaxies in and out of this class. We estimate that galaxies less massive than $10^{10}\rm M_{\odot}$ spend approximately 0.4 Gyr in the green valley. By comparing quenched and early-type populations, we provide further evidence for the ``slow-then-rapid'' quenching model and suggest that it can also be applied to morphological transitions. Our results indicate that morphological transformation occurs at larger radii than complete star-formation quenching. About 75% of galaxies undergoing morphological transition in clusters are spirals evolving into S0s, suggesting that infalling galaxies retain their disks, while massive ellipticals are relics of early merger events. Finally, we show it takes approximately 2.5 and 1.2 Gyr after the delay-time ($\sim 3.8 {\rm Gyr}$) for the population of low mass galaxies in clusters to reach a 50% threshold in quenched and early-type fraction, respectively. These findings suggest morphological transition precedes full star formation quenching, with both processes possibly being causally linked.

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arXiv2024

On the bright-end of the UV luminosity functions of galaxies at $z \sim 0.6-1.2$

We derive the Ultra-Violet (UV) luminosity function (LF) of star-forming galaxies in the redshift range $z = 0.6 - 1.2$, in the rest-frame far-UV ($1500$ Å) wavelength. For this work, we are in particular interested in the bright end of the UV LF in this redshift range. Data from the XMM-Newton Optical Monitor (XMM-OM), near-ultraviolet ($2410-3565$ Å) observations over 1.5 sq. deg of the COSMOS field are employed for this purpose. We compile a source-list of $879$ sources with $UVW1_\mathrm{AB}$ in the range $\sim 21-24$ mags from the wide-area UVW1 image of the COSMOS field in the two bins $0.6 \leq z \leq 0.8$ and $0.8 \leq z \leq 1.2$. The $M_{1500}$ for these sources lies in the interval $[-19.10,-22.50]$. We use the maximum likelihood to fit a Schechter function model to the un-binned data to estimate the parameters (faint-end slope, characteristic magnitude, and normalisation) of the Schechter function. We find the shape of the LF to be consistent with the Schechter model, and the parameters are in fair agreement with other studies conducted using direct measurements of the $1500$Å flux. We see a brightening of the characteristic magnitude as we move from lower ($0.7$) to higher ($1.0$) redshift. The measures for luminosity density are within the error margins of past studies. We examine the brightest sources in our sample for the AGN contribution. These sources are characterised by their spectral energy distributions, integrated infrared luminosities, and morphologies. We also explore their overlap with the brightest IR galaxies in a similar redshift range.

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arXiv2023

The co-evolution of strong AGN and central galaxies in different environments

We exploit a sample of 80,000 SDSS central galaxies to investigate the effect of AGN feedback on their evolution. We trace the demographics of optically-selected AGN (Seyferts) as a function of their internal properties and environment. We find that the preeminence of AGN as the dominant ionising mechanism increases with stellar mass, overtaking star-formation for galaxies with $M_\text{stellar} \geq 10^{11}M_\odot$. The AGN fraction changes systematically with the galaxies' star-formation activity. Within the blue cloud, this fraction increases as star-formation activity declines, reaching a maximum near the green valley ($\sim 17 \pm 4\%$), followed by a decrease as the galaxies transition into the red sequence. This systematic trend provides evidence that AGN feedback plays a key role in regulating and suppressing star formation. In general, Seyfert central galaxies achieve an early-type morphology while they still host residual star formation. This suggests that, in all environments, the morphology of Seyfert galaxies evolves from late- to early-type before their star formation is fully quenched. Stellar mass plays an important role in this morphological transformation: while low mass systems tend to emerge from the green valley with an elliptical morphology (T-Type $\sim -2.5 \pm 0.7$), their high-mass counterparts maintain a spiral morphology deeper into the red sequence. In high-stellar-mass centrals, the fraction of Seyferts increases from early- to late-type galaxies, indicating that AGN feedback may be linked with the morphology and its transformation. Our analysis further suggests that AGN are fuelled by their own host halo gas reservoir, but when in group centrals can also increase their gas reservoir via interactions with satellite galaxies.

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arXiv2022

Testing the role of AGN on the star formation and metal enrichment of "twin galaxies"

We explore the effect of AGN activity on the star formation history of galaxies by analysing the stellar population properties of ten pairs of nearby twin galaxies -- selected as being visually similar except for the presence of an AGN. The selection of such twin samples represents a method to study AGN feedback, as recently proposed by del Moral Castro et al. We use integral field unit (IFU) data from CALIFA, stacked within three fixed apertures. AGN galaxies in a twin pair suggest more evolved stellar populations than their non-AGN counterpart 90% of the time, regardless of aperture size. A comparison with a large sample from SDSS confirms that most twins are representative of the general population, but in each twin the differences between twin members is significant. A set of targeted line strengths reveal the AGN member of a twin pair is older and more metal rich than the non-AGN galaxy, suggesting AGN galaxies in our sample may either have an earlier formation time or follow a different star formation and chemical enrichment history. These results are discussed within two simple, contrasting hypotheses for the role played by AGN in galaxy evolution, which can be tested in the future at a greater detail with the use of larger data sets.

astro-ph.GA↗

arXiv2021

From Blue Cloud to Red Sequence: Evidence of Morphological Transition Prior to Star Formation Quenching

We present a study of a sample of 254 clusters from the SDSS-DR7 Yang Catalog and an auxiliary sample of field galaxies to perform a detailed investigation on how galaxy quenching depends on both environment and galaxy stellar mass. Our samples are restricted to 0.03$\leq$z$\leq$0.1 and we only consider clusters with $\rm log(M_{halo}/M_{\odot}) \geq 14$. Comparing properties of field and cluster galaxies in the Blue Cloud, Green Valley and Red Sequence, we find evidence that field galaxies in the red sequence hosted star formation events $\rm 2.1 \pm 0.7$ Gyr ago, on average, more recently than galaxies in cluster environments. Dissecting the star formation rate vs stellar mass diagram we show how morphology rapidly changes after reaching the green valley region, while the star formation rate keeps decreasing. In addition, we use the relation between location in the projected phase space and infall time to explore the time delay between morphological and specific Star Formation Rate variations. We estimate that the transition from late to early-type morphology happens in $\rm Δt_{inf} \sim$1 Gyr, whereas the quenching of star formation takes $\sim$3 Gyr. The time-scale we estimate for morphological transitions is similar to the expected for the delayed-then-rapid quenching model. Therefore, we suggest that the delay phase is characterized mostly by morphological transition, which then contributes morphological quenching as an additional ingredient in galaxy evolution.

astro-ph.GA↗

arXiv2021

The ultraviolet luminosity function of star-forming galaxies between redshifts of 0.6 and 1.2

We use ultraviolet imaging taken with the XMM-Newton Optical Monitor telescope (XMM-OM), covering 280 square arcminutes in the UVW1 band (effective wavelength 2910 Angstroms) to measure rest-frame ultraviolet (1500 Angstrom) luminosity functions of galaxies with redshifts z between 0.6 and 1.2. The XMM-OM data are supplemented by a large body of optical and infrared imaging to provide photometric redshifts. The XMM-OM data have a significantly narrower point-spread-function (resulting in less source confusion) and simpler K-correction than the GALEX data previously employed in this redshift range. Ultraviolet-bright active galactic nuclei are excluded to ensure that the luminosity functions relate directly to the star-forming galaxy population. Binned luminosity functions and parametric Schechter-function fits are derived in two redshift intervals: 0.6<z<0.8 and 0.8<z<1.2. We find that the luminosity function evolves such that the characteristic absolute magnitude M* is brighter for 0.8<z<1.2 than for 0.6<z<0.8.

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arXiv2021

Constraints on the dust extinction law of the Galaxy with Swift/UVOT, Gaia and 2MASS

We explore variations of the dust extinction law of the Milky Way by selecting stars from the Swift/UVOT Serendipitous Source Catalogue, cross-matched with Gaia DR2 and 2MASS to produce a sample of 10,452 stars out to ~4kpc with photometry covering a wide spectral window. The near ultraviolet passbands optimally encompass the 2175A bump, so that we can simultaneously fit the net extinction, quoted in the V band (A$_V$), the steepness of the wavelength dependence ($δ$) and the bump strength (E$_b$). The methodology compares the observed magnitudes with theoretical stellar atmospheres from the models of Coelho. Significant correlations are found between these parameters, related to variations in dust composition, that are complementary to similar scaling relations found in the more complex dust attenuation law of galaxies - that also depend on the distribution of dust among the stellar populations within the galaxy. We recover the strong anticorrelation between A$_V$ and Galactic latitude, as well as a weaker bump strength at higher extinction. $δ$ is also found to correlate with latitude, with steeper laws towards the Galactic plane. Our results suggest that variations in the attenuation law of galaxies cannot be fully explained by dust geometry.

astro-ph.GA↗

arXiv2021

Mild radial variations of the stellar IMF in the bulge of M31

Using new, homogeneous, long-slit spectroscopy in the wavelength range from ~0.35 to ~1micron, we study radial gradients of optical and near-infrared (NIR) IMF-sensitive features along the major axis of the bulge of M31, out to a galacto-centric distance of ~200'' (~800pc). Based on state-of-the-art stellar population synthesis models with varying Na abundance ratio, we fit a number of spectral indices, from different chemical species (including TiO's, Ca, and Na indices), to constrain the low-mass (<0.5M_Sun) end slope (i.e. the fraction of low-mass stars) of the stellar IMF, as a function of galacto-centric distance. Outside a radial distance of ~10'', we infer an IMF similar to a Milky-Way-like distribution, while at small galacto-centric distances, an IMF radial gradient is detected, with a mildly bottom-heavy IMF in the few inner arcsec. We are able to fit Na features (both NaD and NaI8190), without requiring extremely high Na abundance ratios. [Na/Fe] is ~0.4dex for most of the bulge, rising up to ~0.6dex in the innermost radial bins. Our results imply an overall, luminosity-weighted, IMF and mass-to-light ratio for the M31 bulge, consistent with those for a Milky-Way-like distribution, in contrast to results obtained, in general, for most massive early-type galaxies.

astro-ph.GA↗

arXiv2021

Evaluating hydrodynamical simulations with green valley galaxies

We test cosmological hydrodynamical simulations of galaxy formation regarding the properties of the Blue Cloud (BC), Green Valley (GV) and Red Sequence (RS), as measured on the 4000$\small{ \mathring {\mathrm A}}$ break strength vs stellar mass plane at $z=0.1$. We analyse the RefL0100N1504 run of EAGLE and the TNG100 run of IllustrisTNG project, by comparing them with the Sloan Digital Sky Survey, while taking into account selection bias. Our analysis focuses on the GV, within stellar mass $\log\,\mathrm{M_\star/M_{\odot}} \simeq 10-11$, selected from the bimodal distribution of galaxies on the D$_n$(4000) vs stellar mass plane, following Angthopo et al. methodology. Both simulations match the fraction of AGN in the green-valley. However, they over-produce quiescent GV galaxies with respect to observations, with IllustrisTNG yielding a higher fraction of quiescent GV galaxies than EAGLE. In both, GV galaxies have older luminosity-weighted ages with respect to the SDSS, while a better match is found for mass-weighted ages. We find EAGLE GV galaxies quench their star formation early, but undergo later episodes of star formation, matching observations. In contrast, IllustrisTNG GV galaxies have a more extended SFH, and quench more effectively at later cosmic times, producing the excess of quenched galaxies in GV compared with SDSS, based on the 4000$\small{ \mathring {\mathrm A}}$ break strength. These results suggest the AGN feedback subgrid physics, more specifically, the threshold halo mass for black hole input and the black hole seed mass, could be the primary cause of the over-production of quiescent galaxies found with respect to the observational constraints.

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arXiv2021

Investigating the Projected Phase Space of Gaussian and Non-Gaussian Clusters

By way of the projected phase-space (PPS), we investigate the relation between galaxy properties and cluster environment in a subsample of groups from the Yang Catalog. The sample is split according to the gaussianity of the velocity distribution in the group into gaussian (G) and non-gaussian (NG). Our sample is limited to massive clusters with $\rm M_{200} \geq 10^{14} M_{\odot}$ and $\rm 0.03\leq z \leq 0.1$. NG clusters are more massive, less concentrated and have an excess of faint galaxies compared to G clusters. NG clusters show mixed distributions of galaxy properties in the PPS compared to the G case. Using the relation between infall time and locus on the PPS, we find that, on average, NG clusters accreted $\rm \sim 10^{11}\,M_{\odot}$ more stellar mass in the last $\sim 5$ Gyr than G clusters. The relation between galaxy properties and infall time is significantly different for galaxies in G and NG systems. The more mixed distribution in the PPS of NG clusters translates into shallower relations with infall time. Faint galaxies whose first crossing of the cluster virial radius happened 2-4 Gyr ago in NG clusters are older and more metal-rich than in G systems. All these results suggest that NG clusters experience a higher accretion of pre-processed galaxies, which characterizes G and NG clusters as different environments to study galaxy evolution.

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arXiv2019

Stellar populations of galaxies in the ALHAMBRA survey up to $z \sim 1$. II. Stellar content of quiescent galaxies within the dust-corrected stellar mass$-$colour and the $UVJ$ colour$-$colour diagrams

Our aim is to determine the distribution of stellar population parameters (extinction, age, metallicity, and star formation rate) of quiescent galaxies within the rest-frame stellar mass$-$colour and $UVJ$ colour$-$colour diagrams corrected for extinction up to $z\sim1$. These novel diagrams reduce the contamination in samples of quiescent galaxies owing to dust-reddened galaxies, and they provide useful constraints on stellar population parameters. We set constraints on the stellar population parameters of quiescent galaxies combining the ALHAMBRA multi-filter photo-spectra with our SED-fitting code MUFFIT, making use of composite stellar population models. The extinction obtained by MUFFIT allowed us to remove dusty star-forming (DSF) galaxies from the sample of red $UVJ$ galaxies. The distributions of stellar population parameters across these rest-frame diagrams are revealed after the dust correction and are fitted by the LOESS method to reduce uncertainty effects. Quiescent galaxy samples defined via classical $UVJ$ diagrams are typically contaminated by a $\sim20$% fraction of DSF galaxies. A significant part of the galaxies in the green valley are actually obscured star-forming galaxies ($\sim30-65$%). Consequently, the transition of galaxies from the blue cloud to the red sequence, and hence the related mechanisms for quenching, seems to be much more efficient and faster than previously reported. The rest-frame stellar mass$-$colour and $UVJ$ colour$-$colour diagrams are useful for constraining the age, metallicity, extinction, and star formation rate of quiescent galaxies by only their redshift, rest-frame colours, and/or stellar mass. Dust correction plays an important role in understanding how quiescent galaxies are distributed in these diagrams and is key to performing a pure selection of quiescent galaxies via intrinsic colours.

astro-ph.GA↗

arXiv2019

Stellar populations of galaxies in the ALHAMBRA survey up to $z \sim 1$. IV. Properties of quiescent galaxies on the stellar mass$-$size plane

We perform a comprehensive study of the stellar population properties of quiescent galaxies as a function of size and stellar mass to constrain the physical mechanism governing the stellar mass assembly and the likely evolutive scenarios that explain their growth in size. After selecting all the quiescent galaxies from the ALHAMBRA survey by the dust-corrected stellar mass$-$colour diagram, we built a shared sample of $\sim850$ quiescent galaxies with reliable sizes from the HST. The stellar population properties were retrieved using the SED-fitting code MUFFIT with various sets of composite stellar population models. Age, formation epoch, metallicity, and extinction were studied on the stellar mass$-$size plane as function of size through a Monte Carlo approach. This accounted for uncertainties and degeneracy effects amongst stellar population properties. The stellar population properties of quiescent galaxies and their stellar mass and size since $z\sim1$ are correlated. At fixed stellar mass, the more compact the quiescent galaxy, the older and richer in metals it is ($1$Gyr and $0.1$dex, respectively). In addition, more compact galaxies may present slight lower extinctions than their more extended counterparts at the same stellar mass ($<0.1$ mag). By means of studying constant regions of stellar population properties across the stellar mass$-$size plane, we obtained empirical relations to constrain the physical mechanism that governs the stellar mass assembly of the form $M_\star \propto r_\mathrm{c}^α$, where $α$ amounts to $0.50-0.55 \pm 0.09$. There are indications that support the idea that the velocity dispersion is tightly correlated with the stellar content of galaxies. The mechanisms driving the evolution of stellar populations can therefore be partly linked to the dynamical properties of galaxies, along with their gravitational potential.

astro-ph.GA↗

arXiv2019

IMF radial gradients in most massive early-type galaxies

Using new long-slit spectroscopy obtained with X-Shooter at ESO-VLT, we study, for the first time, radial gradients of optical and Near-Infrared IMF-sensitive features in a representative sample of galaxies at the very high-mass end of the galaxy population. The sample consists of seven early-type galaxies (ETGs) at $z\sim0.05$, with central velocity dispersion in the range $300<σ<350$km/s. Using state-of-art stellar population synthesis models, we fit a number of spectral indices, from different chemical species (including TiO's and Na indices), to constrain the IMF slope (i.e. the fraction of low-mass stars), as a function of galactocentric distance, over a radial range out to $\sim4$kpc. ETGs in our sample show a significant correlation of IMF slope and surface mass density. The bottom-heavy population (i.e. an excess of low-mass stars in the IMF) is confined to central galaxy regions with surface mass density above $\sim 10^{10} M_\odot kpc^{-2}$, or, alternatively, within a characteristic radius of $\sim2$~kpc. Radial distance, in physical units, and surface mass density, are the best correlators to IMF variations, with respect to other dynamical (e.g. velocity dispersion) and stellar population (e.g. metallicity) properties. Our results for the most massive galaxies suggest that there is no single parameter} that fully explains variations in the stellar IMF, but IMF radial profiles at z$\sim$0 rather result from the complex formation and mass accretion history of galaxy inner and outer regions.

astro-ph.GA↗

arXiv2019

Chronos: A NIR spectroscopic survey to target the most important phases of galaxy evolution across cosmic time

(Abridged summary) Responding to ESA's Voyage 2050 call to define the long-term plan for the future space missions that will address the astrophysics science questions during the 2035-2050 cycle, we propose a dedicated, ultra-deep spectroscopic survey in the near infrared (NIR), that will target a mass-limited sample of galaxies during two of the most fundamental epochs of cosmic evolution: the formation of the first galaxies (at z>6; cosmic dawn), and at the peak of galaxy formation activity (between redshift z=1 and 3; cosmic noon). By way of NIR observations, it is possible to study the Lyman-alpha region in the former, and the optical rest-frame in the latter, allowing us to extract fundamental observables such as gas and stellar kinematics, chemical abundances, and ages, providing a unique legacy database covering these two crucial stages of cosmic evolution. A dedicated, space-based facility will overcome the challenges faced by ground-based telescopes, no matter how large the aperture, or the reduced field of view and low multiplex factor of the best space-based instrument in the near future, namely NIRSpec at the JWST. Our project (codename Chronos) aims to produce about 1 million high quality spectra, with a high S/N in the continuum, where information about the underlying stellar populations is encoded.

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