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Faber, S. M.

Publications and source records attributed to Faber, S. M..

At least 19 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2021

What is Important? Morphological Asymmetries are Useful Predictors of Star Formation Rates of Star-forming Galaxies in SDSS Stripe 82

The morphology and structure of galaxies reflect their star formation and assembly histories. We use the framework of mutual information (MI) to quantify the interdependence among several structural variables and to rank them according to their relevance for predicting the specific star formation rate (SSFR) by comparing the MI of the predictor variables with the SSFR and penalizing variables that are redundant. We apply this framework to study ~3700 face-on star-forming galaxies (SFGs) with varying degrees of bulge dominance and central concentration and with stellar mass $M$ * ≈ 10 9 $M$ ⊙ at redshift $z$ = 0.02–0.12. We use the Sloan Digital Sky Survey (SDSS) Stripe 82 deep $i$-band imaging data, which improve measurements of asymmetry and bulge dominance indicators. We find that star-forming galaxies are a multiparameter family. In addition to $M$ * , asymmetry emerges as the most powerful predictor of SSFR residuals of SFGs, followed by bulge prominence/concentration. Star-forming galaxies with higher asymmetry and stronger bulges have higher SSFR at a given $M$ * . In conclusion, the asymmetry reflects both irregular spiral arms and lopsidedness in seemingly isolated SFGs and structural perturbations by galaxy interactions or mergers.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2020

Structural and stellar-population properties versus bulge types in Sloan Digital Sky Survey central galaxies

ABSTRACT This paper studies pseudo-bulges (P-bulges) and classical bulges (C-bulges) in Sloan Digital Sky Survey (SDSS) central galaxies using the new bulge indicator ΔΣ1, which measures relative central stellar-mass surface density within 1 kpc. We compare ΔΣ1 to the established bulge-type indicator Δ〈μe〉 from Gadotti (2009) and show that classifying by ΔΣ1 agrees well with Δ〈μe〉. ΔΣ1 requires no bulge–disc decomposition and can be measured on SDSS images out to z = 0.07. Bulge types using it are mapped on to 20 different structural and stellar-population properties for 12 000 SDSS central galaxies with masses 10.0 < log M*/M⊙ < 10.4. New trends emerge from this large sample. Structural parameters show fairly linear log–log relations versus ΔΣ1 and Δ〈μe〉 with only moderate scatter, while stellar-population parameters show a highly non-linear ‘elbow’ in which specific star formation rate remains roughly flat with increasing central density and then falls rapidly at the elbow, where galaxies begin to quench. P-bulges occupy the low-density end of the horizontal arm of the elbow and are universally star forming, while C-bulges occupy the elbow and the vertical branch and exhibit a wide range of star formation rates at a fixed density. The non-linear relation between central density and star formation rate has been seen before, but this mapping on to bulge class is new. The wide range of star formation rates in C-bulges helps to explain why bulge classifications using different parameters have sometimes disagreed in the past. The elbow-shaped relation between density and stellar indices suggests that central structure and stellar populations evolve at different rates as galaxies begin to quench.

Luo, Yifei↗
DOE OSTI2019

Deep ugrizY imaging and DEEP2/3 spectroscopy: a photometric redshift testbed for LSST and public release of data from the DEEP3 Galaxy Redshift Survey

ABSTRACT We present catalogues of calibrated photometry and spectroscopic redshifts in the Extended Groth Strip, intended for studies of photometric redshifts (photo-z’s). The data includes ugriz photometry from Canada–France–Hawaii Telescope Legacy Survey (CFHTLS) and Y-band photometry from the Subaru Suprime camera, as well as spectroscopic redshifts from the DEEP2, DEEP3, and 3D-HST surveys. These catalogues incorporate corrections to produce effectively matched-aperture photometry across all bands, based upon object size information available in the catalogue and Moffat profile point spread function fits. We test this catalogue with a simple machine learning-based photometric redshift algorithm based upon Random Forest regression, and find that the corrected aperture photometry leads to significant improvement in photo-z accuracy compared to the original SExtractor catalogues from CFHTLS and Subaru. The deep ugrizY photometry and spectroscopic redshifts are well suited for empirical tests of photometric redshift algorithms for LSST. The resulting catalogues are publicly available at http://d-scholarship.pitt.edu/36064/. We include a basic summary of the strategy of the DEEP3 Galaxy Redshift Survey to accompany the recent public release of DEEP3 data.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2019

The evolution of galaxy shapes in CANDELS: from prolate to discy

In this study, we model the projected b/a – log a distributions of CANDELS star-forming main-sequence galaxies, where a (b) is the half-light semimajor (semiminor) axis of the galaxy images measured by GALFIT . We find that smaller a galaxies are rounder at all stellar masses M* and redshifts, so we include a when analysing b/a distributions. Approximating intrinsic shapes of the galaxies as triaxial ellipsoids and assuming a multivariate normal distribution of galaxy size and two shape parameters, we construct their intrinsic shape and size distributions to obtain the fractions of elongated (prolate), discy (oblate), and spheroidal galaxies in each redshift and mass bin. We find that galaxies tend to be prolate at low M* and high redshifts, and discy at high M* and low redshifts, qualitatively consistent with van der Wel et al., implying that galaxies tend to evolve from prolate to discy. These results are consistent with the predictions from simulations that the transition from prolate to oblate is caused by a compaction event at a characteristic mass range, making the galaxy centre baryon dominated. We give probabilities of a galaxy’s being elongated, discy, or spheroidal as a function of its M* , redshift, and projected b/a and a , which can facilitate target selections of galaxies with specific shapes at high redshifts.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2018

Evidence for Merger-driven Growth in Luminous, High- z , Obscured AGNs in the CANDELS/COSMOS Field

While major mergers have long been proposed as a driver of both active galactic nucleus (AGN) activity and the ${M}_{\mathrm{BH}}\mbox{--}{\sigma }_{\mathrm{bulge}}$ relation, studies of moderate to high-redshift Seyfert-luminosity AGN hosts have found little evidence for enhanced rates of interactions. However, both theory and observation suggest that while these AGNs may be fueled by stochastic accretion and secular processes, high-luminosity, high-redshift, and heavily obscured AGNs are the AGNs most likely to be merger-driven. To better sample this population of AGNs, we turn to infrared selection in the CANDELS/COSMOS field. Compared to their lower-luminosity and less obscured X-ray-only counterparts, IR-only AGNs (luminous, heavily obscured AGNs) are more likely to be classified as either irregular (${50}_{-12}^{+12} \% $ versus ${9}_{-2}^{+5} \% $) or asymmetric (${69}_{-13}^{+9} \% $ versus ${17}_{-4}^{+6} \% $) and are less likely to have a spheroidal component (${31}_{-9}^{+13} \% $ versus ${77}_{-6}^{+4} \% $). Furthermore, IR-only AGNs are also significantly more likely than X-ray-only AGNs (${75}_{-13}^{+8} \% $ versus ${31}_{-6}^{+6} \% $) to be classified either as interacting or merging in a way that significantly disturbs the host galaxy or as disturbed, though not clearly interacting or merging, which potentially represents the late stages of a major merger. Finally, this suggests that while major mergers may not contribute significantly to the fueling of Seyfert-luminosity AGNs, interactions appear to play a more dominant role in the triggering and fueling of high-luminosity heavily obscured AGNs.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2017

CANDELS: Elevated Black Hole Growth in the Progenitors of Compact Quiescent Galaxies at z ∼ 2

We examine the fraction of massive (M{sub ∗}>10{sup 10} M{sub ⊙}) compact star-forming galaxies (cSFGs) that host an active galactic nucleus (AGN) at z∼2. These cSFGs are likely the direct progenitors of the compact quiescent galaxies observed at this epoch, which are the first population of passive galaxies to appear in large numbers in the early Universe. We identify cSFGs that host an AGN using a combination of Hubble WFC3 imaging and Chandra X-ray observations in four fields: the Chandra Deep Fields, the Extended Groth Strip, and the UKIDSS Ultra Deep Survey field. We find that 39.2{sub −3.6}{sup +3.9}% (65/166) of cSFGs at 1.4<z<3.0 host an X-ray detected AGN. This fraction is 3.2 times higher than the incidence of AGN in extended star-forming galaxies with similar masses at these redshifts. This difference is significant at the 6.2σ level. Our results are consistent with models in which cSFGs are formed through a dissipative contraction that triggers a compact starburst and concurrent growth of the central black hole. We also discuss our findings in the context of cosmological galaxy evolution simulations that require feedback energy to rapidly quench cSFGs. We show that the AGN fraction peaks precisely where energy injection is needed to reproduce the decline in the number density of cSFGs with redshift. Our results suggest that the first abundant population of massive quenched galaxies emerged directly following a phase of elevated supermassive black hole growth and further hints at a possible connection between AGN and the rapid quenching of star formation in these galaxies.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2017

On the Evolution of the Central Density of Quiescent Galaxies

We investigate the origin of the evolution of the population-averaged central stellar mass density (Σ{sub 1}) of quiescent galaxies (QGs) by probing the relation between stellar age and Σ{sub 1} at z ∼ 0. We use the Zurich ENvironmental Study (ZENS), which is a survey of galaxy groups with a large fraction of satellite galaxies. QGs shape a narrow locus in the Σ{sub 1}– M {sub ⋆} plane, which we refer to as Σ{sub 1} ridgeline. Colors of ( B − I ) and ( I − J ) are used to divide QGs into three age categories: young (<2 Gyr), intermediate (2–4 Gyr), and old (>4 Gyr). At fixed stellar mass, old QGs on the Σ{sub 1} ridgeline have higher Σ{sub 1} than young QGs. This shows that galaxies landing on the Σ{sub 1} ridgeline at later epochs arrive with lower Σ{sub 1}, which drives the zeropoint of the ridgeline down with time. We compare the present-day zeropoint of the oldest population at z = 0 with the zeropoint of the quiescent population 4 Gyr back in time, at z = 0.37. These zeropoints are identical, showing that the intrinsic evolution of individual galaxies after they arrive on the Σ{sub 1} ridgeline must be negligible, or must evolve parallel to the ridgeline during this interval. The observed evolution of the global zeropoint of 0.07 dex over the last 4 Gyr is thus largely due to the continuous addition of newly quenched galaxies with lower Σ{sub 1} at later times (“progenitor bias”). While these results refer to the satellite-rich ZENS sample as a whole, our work suggests a similar age–Σ{sub 1} trend for central galaxies.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2017

No Evidence for Feedback: Unexceptional Low-ionization Winds in Host Galaxies of Low Luminosity Active Galactic Nuclei at Redshift z ∼ 1

We study winds in 12 X-ray AGN host galaxies at z∼1. We find, using the low-ionization Fe ii λ2586 absorption in the stacked spectra, that the probability distribution function (PDF) of the centroid-velocity shift in AGNs has 50th (median), 16th, and 84th percentiles of (−87, −251, +86) km s{sup −1} respectively. The PDF of the velocity dispersion in AGNs has 50th (median), 84th, and 16th percentiles of (139, 253, 52) km s{sup −1} respectively. The centroid velocity and the velocity dispersions are obtained from a two-component (ISM+wind) absorption-line model. The equivalent width PDF of the outflow in AGNs has 50th (median), 84th, and 16th percentiles of (0.4, 0.8, 0.1) Å. There is a strong ISM component in Fe ii λ2586 absorption (with (1.2, 1.5, 0.8) Å, implying the presence of a substantial amount cold gas in the host galaxies. For comparison, star-forming and X-ray undetected galaxies at a similar redshift, matched roughly in stellar mass and galaxy inclination, have a centroid-velocity PDF with percentiles of (−74, −258, +90) km s{sup −1}, and a velocity-dispersion PDF with percentiles of (150, 259, 57) km s{sup −1}. Thus, winds in the AGN are similar to star formation-driven winds, and are too weak to escape and expel substantial cool gas from galaxies. Our sample doubles the previous sample of AGNs studied at z∼0.5 and extends the analysis to z∼1. A joint reanalysis of the z∼0.5 AGN sample and our sample yields consistent results to the measurements above.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2017

CANDELS Sheds Light on the Environmental Quenching of Low-mass Galaxies

We investigate the environmental quenching of galaxies, especially those with stellar masses (M {sub *}) < 10{sup 9.5} M {sub ⊙}, beyond the local universe. Essentially all local low-mass quenched galaxies (QGs) are believed to live close to massive central galaxies, which is a demonstration of environmental quenching. We use CANDELS data to test whether or not such a dwarf QG-massive central galaxy connection exists beyond the local universe. For this purpose, we only need a statistically representative, rather than complete, sample of low-mass galaxies, which enables our study to z ≳ 1.5. For each low-mass galaxy, we measure the projected distance (d {sub proj}) to its nearest massive neighbor (M {sub *} > 10{sup 10.5} M {sub ⊙}) within a redshift range. At a given z and M {sub *}, the environmental quenching effect is considered to be observed if the d {sub proj} distribution of QGs (d{sub proj}{sup Q}) is significantly skewed toward lower values than that of star-forming galaxies (d{sub proj}{sup SF}). For galaxies with 10{sup 8} M {sub ⊙} < M {sub *} < 10{sup 10} M {sub ⊙}, such a difference between d{sub proj}{sup Q} and d{sub proj}{sup SF} is detected up to z ∼ 1. Also, about 10% of the quenched galaxies in our sample are located between two and four virial radii (R {sub Vir}) of the massive halos. The median projected distance from low-mass QGs to their massive neighbors, d{sub proj}{sup Q}/R{sub Vir}, decreases with satellite M {sub *} at M {sub *} ≲ 10{sup 9.5} M {sub ⊙}, but increases with satellite M {sub *} at M {sub *} ≳ 10{sup 9.5} M {sub ⊙}. This trend suggests a smooth, if any, transition of the quenching timescale around M {sub *} ∼ 10{sup 9.5} M {sub ⊙} at 0.5 < z < 1.0.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2017

CANDELS Multi-Wavelength Catalogs: Source identification and photometry in the CANDELS COSMOS survey field

We present a multi-wavelength photometric catalog in the COSMOS field as part of the observations by the Cosmic Assembly Near-infrared Deep Extragalactic Legacy Survey. The catalog is based on Hubble Space Telescope Wide Field Camera 3 (HST/WFC3) and Advanced Camera for Surveys observations of the COSMOS field (centered at R.A.: 10{sup h}00{sup m}28{sup s}, Decl.: +02{sup ∘}12{sup ′}21{sup ′′}). The final catalog has 38671 sources with photometric data in 42 bands from UV to the infrared (∼0.3--8 μm). This includes broadband photometry from HST, CFHT, Subaru, the Visible and Infrared Survey Telescope for Astronomy, and Spitzer Space Telescope in the visible, near-infrared, and infrared bands along with intermediate- and narrowband photometry from Subaru and medium-band data from Mayall NEWFIRM. Source detection was conducted in the WFC3 F160W band (at 1.6 μm) and photometry is generated using the Template FITting algorithm. We further present a catalog of the physical properties of sources as identified in the HST F160W band and measured from the multi-band photometry by fitting the observed spectral energy distributions of sources against templates.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2016

THE BURSTY STAR FORMATION HISTORIES OF LOW-MASS GALAXIES AT 0.4 < z < 1 REVEALED BY STAR FORMATION RATES MEASURED FROM H β AND FUV

We investigate the burstiness of star formation histories (SFHs) of galaxies at 0.4 < z < 1 by using the ratio of star formation rates (SFRs) measured from H β and FUV (1500 Å) (H β -to-FUV ratio). Our sample contains 164 galaxies down to stellar mass ( M {sub *}) of 10{sup 8.5} M {sub ⊙} in the CANDELS GOODS-N region, where Team Keck Redshift Survey Keck/DEIMOS spectroscopy and Hubble Space Telescope /WFC3 F275W images from CANDELS and Hubble Deep UV Legacy Survey are available. When the ratio of H β - and FUV-derived SFRs is measured, dust extinction correction is negligible (except for very dusty galaxies) with the Calzetti attenuation curve. The H β -to-FUV ratio of our sample increases with M {sub *} and SFR. The median ratio is ∼0.7 at M {sub *} ∼ 10{sup 8.5} M {sub ⊙} (or SFR ∼ 0.5 M {sub ⊙} yr{sup −1}) and increases to ∼1 at M {sub *} ∼ 10{sup 10} M {sub ⊙} (or SFR ∼ 10 M {sub ⊙} yr{sup −1}). At M {sub *} < 10{sup 9.5} M {sub ⊙}, our median H β -to-FUV ratio is lower than that of local galaxies at the same M {sub *}, implying a redshift evolution. Bursty SFH on a timescale of a few tens of megayears on galactic scales provides a plausible explanation for our results, and the importance of the burstiness increases as M {sub *} decreases. Due to sample selection effects, our H β -to-FUV ratio may be an upper limit of the true value of a complete sample, which strengthens our conclusions. Other models, e.g., non-universal initial mass function or stochastic star formation on star cluster scales, are unable to plausibly explain our results.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2016

Sub-kiloparsec ALMA imaging of compact star-forming galaxies at z ∼ 2.5: revealing the formation of dense galactic cores in the progenitors of compact quiescent galaxies

We present spatially resolved Atacama Large Millimeter/submillimeter Array (ALMA) 870 μm dust continuum maps of six massive, compact, dusty star-forming galaxies at z ∼ 2.5. These galaxies are selected for their small rest-frame optical sizes (r{sub e,F160W}∼1.6 kpc) and high stellar mass densities that suggest that they are direct progenitors of compact quiescent galaxies at z ∼ 2. The deep observations yield high far-infrared (FIR) luminosities of L{sub IR}=10{sup 12.3−12.8} L{sub ⊙} and star formation rates (SFRs) of SFR = 200–700 M {sub ⊙} yr{sup −1}, consistent with those of typical star-forming “main sequence” galaxies. The high spatial resolution (FWHM ∼ 0.″12–0.″18) ALMA and Hubble Space Telescope photometry are combined to construct deconvolved, mean radial profiles of their stellar mass and (UV+IR) SFR. We find that the dusty, nuclear IR–SFR overwhelmingly dominates the bolometric SFR up to r ∼ 5 kpc, by a factor of over 100× from the unobscured UV–SFR. Furthermore, the effective radius of the mean SFR profile (r{sub e,SFR}∼1 kpc) is ∼30% smaller than that of the stellar mass profile. The implied structural evolution, if such nuclear starburst last for the estimated gas depletion time of Δt = ±100 Myr, is a 4× increase of the stellar mass density within the central 1 kpc and a 1.6× decrease of the half-mass–radius. This structural evolution fully supports dissipation-driven, formation scenarios in which strong nuclear starbursts transform larger, star-forming progenitors into compact quiescent galaxies.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2016

Breaking the curve with candels: a Bayesian approach to reveal the non-universality of the dust-attenuation law at high redshift

Dust attenuation affects nearly all observational aspects of galaxy evolution, yet very little is known about the form of the dust-attenuation law in the distant universe. Here, we model the spectral energy distributions of galaxies at z ∼ 1.5–3 from CANDELS with rest-frame UV to near-IR imaging under different assumptions about the dust law, and compare the amount of inferred attenuated light with the observed infrared (IR) luminosities. Some individual galaxies show strong Bayesian evidence in preference of one dust law over another, and this preference agrees with their observed location on the plane of infrared excess (IRX, L{sub TIR}/L{sub UV}) and UV slope (β). We generalize the shape of the dust law with an empirical model, A{sub λ,δ}=E(B−V)k{sub λ}(λ/λ{sub V}){sup δ} where k {sub λ} is the dust law of Calzetti et al., and show that there exists a correlation between the color excess E(B−V) and tilt δ with δ=(0.62±0.05)log(E(B−V))+(0.26±0.02). Galaxies with high color excess have a shallower, starburst-like law, and those with low color excess have a steeper, SMC-like law. Surprisingly, the galaxies in our sample show no correlation between the shape of the dust law and stellar mass, star formation rate, or β. The change in the dust law with color excess is consistent with a model where attenuation is caused by scattering, a mixed star–dust geometry, and/or trends with stellar population age, metallicity, and dust grain size. This rest-frame UV-to-near-IR method shows potential to constrain the dust law at even higher redshifts (z>3).

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2016

( Chandra Chandra) counterparts of CANDELS GOODS-S sources

Improving the capabilities of detecting faint X-ray sources is fundamental for increasing the statistics on faint high-z active galactic nuclei (AGNs) and star-forming galaxies (SFGs). We performed a simultaneous maximum likelihood point-spread function fit in the [0.5–2] keV and [2–7] keV energy bands of the 4 Ms Chandra Deep Field South (CDFS) data at the position of the 34,930 CANDELS H-band selected galaxies. For each detected source we provide X-ray photometry and optical counterpart validation. We validated this technique by means of a ray-tracing simulation. We detected a total of 698 X-ray point sources with a likelihood L>4.98 (i.e., >2.7σ). We show that prior knowledge of a deep sample of optical–NIR galaxies leads to a significant increase in the detection of faint (i.e., ∼10{sup −17} cgs in the [0.5–2] keV band) sources with respect to “blind” X-ray detections. By including previous X-ray catalogs, this work increases the total number of X-ray sources detected in the 4 Ms CDFS, CANDELS area to 793, which represents the largest sample of extremely faint X-ray sources assembled to date. Our results suggest that a large fraction of the optical counterparts of our X-ray sources determined by likelihood ratio actually coincides with the priors used for the source detection. Most of the new detected sources are likely SFGs or faint, absorbed AGNs. We identified a few sources with putative photometric redshift z > 4. Despite the low number statistics and the uncertainties on the photo z, this sample significantly increases the number of X-ray-selected candidate high-z AGNs.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2016

STELLAR MASS–GAS-PHASE METALLICITY RELATION AT 0.5 ≤ z ≤ 0.7: A POWER LAW WITH INCREASING SCATTER TOWARD THE LOW-MASS REGIME

We present the stellar mass (M{sub ∗})–gas-phase metallicity relation (MZR) and its scatter at intermediate redshifts (0.5⩽z⩽0.7) for 1381 field galaxies collected from deep spectroscopic surveys. The star formation rate (SFR) and color at a given M{sub ∗} of this magnitude-limited (R≲24 AB) sample are representative of normal star-forming galaxies. For masses below 10{sup 9} M{sub ⊙}, our sample of 237 galaxies is ∼10 times larger than those in previous studies beyond the local universe. This huge gain in sample size enables superior constraints on the MZR and its scatter in the low-mass regime. We find a power-law MZR at 10{sup 8} M{sub ⊙} < M{sub ∗} < 10{sup 11} M{sub ⊙}: 12+log(O/H)=(5.83±0.19) +(0.30±0.02)log(M{sub ∗}/M{sub ⊙}). At 10{sup 9} M{sub ⊙} < M{sub ∗} < 10{sup 10.5} M{sub ⊙}, our MZR shows agreement with others measured at similar redshifts in the literature. Our power-law slope is, however, shallower than the extrapolation of the MZRs of others to masses below 10{sup 9} M{sub ⊙}. The SFR dependence of the MZR in our sample is weaker than that found for local galaxies (known as the fundamental metallicity relation). Compared to a variety of theoretical models, the slope of our MZR for low-mass galaxies agrees well with predictions incorporating supernova energy-driven winds. Being robust against currently uncertain metallicity calibrations, the scatter of the MZR serves as a powerful diagnostic of the stochastic history of gas accretion, gas recycling, and star formation of low-mass galaxies. Our major result is that the scatter of our MZR increases as M{sub ∗} decreases. Our result implies that either the scatter of the baryonic accretion rate (σ{sub M-dot }) or the scatter of the M{sub ∗}–M{sub halo} relation (σ{sub SHMR}) increases as M{sub ∗} decreases. Moreover, our measure of scatter at z=0.7 appears consistent with that found for local galaxies. This lack of redshift evolution constrains models of galaxy evolution to have both σ{sub M-dot }and σ{sub SHMR} remain unchanged from z=0.7 to z = 0.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2016

THE UV–OPTICAL COLOR GRADIENTS IN STAR-FORMING GALAXIES AT 0.5 < z < 1.5: ORIGINS AND LINK TO GALAXY ASSEMBLY

The rest-frame UV–optical (i.e., NUV − B ) color index is sensitive to the low-level recent star formation and dust extinction, but it is insensitive to the metallicity. In this Letter, we have measured the rest-frame NUV − B color gradients in ∼1400 large ( r {sub e} > 0.″18), nearly face-on ( b / a > 0.5) main sequence star-forming galaxies (SFGs) between redshift 0.5 and 1.5 in the CANDELS/GOODS-S and UDS fields. With this sample, we study the origin of UV–optical color gradients in the SFGs at z ∼ 1 and discuss their link with the buildup of stellar mass. We find that the more massive, centrally compact, and more dust extinguished SFGs tend to have statistically more negative raw color gradients (redder centers) than the less massive, centrally diffuse, and less dusty SFGs. After correcting for dust reddening based on optical-spectral energy distribution fitting, the color gradients in the low-mass ( M {sub *} < 10{sup 10} M {sub ⊙}) SFGs generally become quite flat, while most of the high-mass ( M {sub *} > 10{sup 10.5} M {sub ⊙}) SFGs still retain shallow negative color gradients. These findings imply that dust reddening is likely the principal cause of negative color gradients in the low-mass SFGs, while both increased central dust reddening and buildup of compact old bulges are likely the origins of negative color gradients in the high-mass SFGs. These findings also imply that at these redshifts the low-mass SFGs buildup their stellar masses in a self-similar way, while the high-mass SFGs grow inside out.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2015

A catalog of visual-like morphologies in the 5 CANDELS fields using deep learning

We present a catalog of visual-like H-band morphologies of ∼50.000 galaxies (H{sub f160w} < 24.5) in the 5 CANDELS fields (GOODS-N, GOODS-S, UDS, EGS, and COSMOS). Morphologies are estimated using Convolutional Neural Networks (ConvNets). The median redshift of the sample is 〈z〉∼1.25. The algorithm is trained on GOODS-S, for which visual classifications are publicly available, and then applied to the other 4 fields. Following the CANDELS main morphology classification scheme, our model retrieves for each galaxy the probabilities of having a spheroid or a disk, presenting an irregularity, being compact or a point source, and being unclassifiable. ConvNets are able to predict the fractions of votes given to a galaxy image with zero bias and ∼10% scatter. The fraction of mis-classifications is less than 1%. Our classification scheme represents a major improvement with respect to Concentration-Asymmetry-Smoothness-based methods, which hit a 20%–30% contamination limit at high z. The catalog is released with the present paper via the Rainbow database (http://rainbowx.fis.ucm.es/Rainbow-navigator-public/).

79 ASTRONOMY AND ASTROPHYSICS↗