Search

We study spatially resolved properties (on spatial scales of $\sim 1-2$ kpc out to at least $3$ effective radii) of the stars, dust, and gas in ten nearby spiral galaxies. The properties of the stellar population and dust are derived by fitting the spatially resolved spectral energy distribution (SED) with more than 20 photometric bands ranging from far-ultraviolet to far-infrared. Our newly developed software piXedfit performs point spread function matching of images, pixel binning, and models the stellar light, dust attenuation, dust emission, and emission from a dusty torus heated by an active galactic nucleus simultaneously through the energy balance approach. With this self-consistent analysis, we present the spatially resolved version of the IRX--$\beta$ relation, finding that it is consistent with the relationship from the integrated photometry. We show that the old stellar populations contribute to the dust heating, which causes an overestimation of star formation rate (SFR) derived from the total ultraviolet and infrared luminosities on kpc scales. With archival high-resolution maps of atomic and molecular gas, we study the radial variation of the properties of the stellar populations (including stellar mass, age, metallicity, and SFR), dust (including dust mass, dust temperature, and abundance of polycyclic aromatic hydrocarbon), gas, as well as dust-to-stellar mass and dust-to-gas mass ratios. We observe a depletion of molecular gas mass fraction in the central region of the majority of the galaxies, suggesting that the lack of available fuel is an important factor in suppressing the specific SFR at the center., Comment: 35 pages, 19 figures, 4 tables. Accepted by ApJ (results remain the same). Complementary figures to Fig. 4 (for 10 galaxies) and high resolution version of Fig. 8 are available at https://github.com/aabdurrouf/maps-nearby-galaxies

We publicly release the spectroscopic and photometric redshift catalog of the sources detected with Chandra in the field of the $z$=6.3 quasar SDSS J1030+0525. This is currently the fifth deepest X-ray field, and reaches a 0.5-2 keV flux limit $f_{\rm 0.5-2}$=6$\times$10$^{-17}$ erg s$^{-1}$ cm$^{-2}$. By using two independent methods, we measure a photometric redshift for 243 objects, while 123 (51%) sources also have a spectroscopic redshift, 110 of which coming from an INAF-Large Binocular Telescope (LBT) Strategic Program. We use the spectroscopic redshifts to determine the quality of the photometric ones, and find it in agreement with that of other X-ray surveys which used a similar number of photometric data-points. In particular, we measure a sample normalized median absolute deviation $\sigma_{NMAD}$=1.48||$z_{phot}$-$z_{spec}$||/(1+$z_{spec}$)=0.065. We use these new spectroscopic and photometric redshifts to study the properties of the Chandra J1030 field. We observe several peaks in our spectroscopic redshift distribution between $z$=0.15 and $z$=1.5, and find that the sources in each peak are often distributed across the whole Chandra field of view. This evidence confirms that X-ray selected AGN can efficiently track large-scale structures over physical scales of several Mpc. Finally, we computed the Chandra J1030 $z>$3 number counts: while the spectroscopic completeness at high-redshift of our sample is limited, our results point towards a potential source excess at $z\geq$4, which we plan to either confirm or reject in the near future with dedicated spectroscopic campaigns., Comment: 21 pages, 15 figures. Accepted for publication in Astronomy and Astrophysics

We present the largest systematic, HST-based search to date for luminous $z\gtrsim8$ galaxy candidates using $\sim$1267 arcmin$^{2}$ of (pure-)parallel observations from a compilation of 288 random sightlines with ACS and WFC3 observations, derived from the SuperBoRG data set and together representing a factor $\sim1.12\times$ larger than existing space-based data sets. Using NIR color cuts and careful photo-$z$ analyses, we find 31 $z\gtrsim8$ galaxy candidates over 29 unique sightlines, and derive global galaxy properties such as UV magnitudes and continuum slopes, sizes, and rest-frame optical properties (e.g., SFRs, stellar masses, $A_{\rm v}$). Taking advantage of the (pure-)parallel nature of our data set - making it one of the most representative thus far - and derived SFRs, we evaluate the cosmic star formation rate density for the bright end of the UV luminosity function at $z\sim8-10$ and test the validity of luminosity function-derived results using a conversion factor. We find our method yields comparable results to those derived with luminosity functions. Furthermore, we present follow up observations of 5 (Super)BoRG targets with Keck/MOSFIRE, finding no evidence of Ly$\alpha$ in $>3$ hrs of $Y-$band observations in either, consistent with a largely neutral medium at $z\sim8$. Our results offer a definitive HST legacy on the bright end of the luminosity function and provide a valuable benchmark as well as targets for follow up with JWST., Comment: 33 pages, 15 figures, 8 tables. Accepted for publication in ApJ (in press). New version reflects important modifications to the derived sample made after discussions with the referee

We measure the size-mass relation and its evolution between redshifts 1$3\times10^{9}M_{\odot}$ at 1$5 \times 10^{9} M_{\odot}$ at 2.5$

We report upon three years of follow-up and confirmation of doubly imaged quasar lenses through imaging campaigns from 2016-2018 with the Near-Infrared Camera2 (NIRC2) on the W. M. Keck Observatory. A sample of 57 quasar lens candidates are imaged in adaptive-optics-assisted or seeing-limited $K^\prime$-band observations. Out of these 57 candidates, 15 are confirmed as lenses. We form a sample of 20 lenses adding in a number of previously-known lenses that were imaged with NIRC2 in 2013-14 as part of a pilot study. By modelling these 20 lenses, we obtain $K^\prime$-band relative photometry and astrometry of the quasar images and the lens galaxy. We also provide the lens properties and predicted time delays to aid planning of follow-up observations necessary for various astrophysical applications, e.g., spectroscopic follow-up to obtain the deflector redshifts for the newly confirmed systems. We compare the departure of the observed flux ratios from the smooth-model predictions between doubly and quadruply imaged quasar systems. We find that the departure is consistent between these two types of lenses if the modelling uncertainty is comparable., Comment: 11 pages, 8 figures, 5 tables. This version: accepted to MNRAS

One of the main challenges in using high redshift active galactic nuclei to study the correlations between the mass of the supermassive Black Hole (MBH) and the properties of their active host galaxies is instrumental resolution. Strong lensing magnification effectively increases instrumental resolution and thus helps to address this challenge. In this work, we study eight strongly lensed active galactic nuclei (AGN) with deep Hubble Space Telescope imaging, using the lens modelling code Lenstronomy to reconstruct the image of the source. Using the reconstructed brightness of the host galaxy, we infer the host galaxy stellar mass based on stellar population models. MBH are estimated from broad emission lines using standard methods. Our results are in good agreement with recent work based on non-lensed AGN, demonstrating the potential of using strongly lensed AGNs to extend the study of the correlations to higher redshifts. At the moment, the sample size of lensed AGN is small and thus they provide mostly a consistency check on systematic errors related to resolution for the non-lensed AGN. However, the number of known lensed AGN is expected to increase dramatically in the next few years, through dedicated searches in ground and space based wide field surveys, and they may become a key diagnostic of black hole and galaxy co-evolution., Comment: 12 pages, 4 figures, 3 tables. MNRAS in press. Comments welcome

We present hitherto the largest sample of gas-phase metallicity radial gradients measured at sub-kiloparsec resolution in star-forming galaxies in the redshift range of $z\in[1.2, 2.3]$. These measurements are enabled by the synergy of slitless spectroscopy from the Hubble Space Telescope near-infrared channels and the lensing magnification from foreground galaxy clusters. Our sample consists of 76 galaxies with stellar mass ranging from 10$^7$ to 10$^{10}$ $M_\odot$, instantaneous star-formation rate in the range of [1, 100] $M_\odot$/yr, and global metallicity [$\frac{1}{12}$, 2] solar. At 2-$\sigma$ confidence level, 15/76 galaxies in our sample show negative radial gradients, whereas 7/76 show inverted gradients. Combining ours and all other metallicity gradients obtained at similar resolution currently available in the literature, we measure a negative mass dependence of $\Delta\log({\rm O/H})/\Delta r~ [\mathrm{dex~kpc^{-1}}] = \left(-0.020\pm0.007\right) + \left(-0.016\pm0.008\right) \log(M_\ast/10^{9.4} M_\odot)$ with the intrinsic scatter being $\sigma=0.060\pm0.006$ over four orders of magnitude in stellar mass. Our result is consistent with strong feedback, not secular processes, being the primary governor of the chemo-structural evolution of star-forming galaxies during the disk mass assembly at cosmic noon. We also find that the intrinsic scatter of metallicity gradients increases with decreasing stellar mass and increasing specific star-formation rate. This increase in the intrinsic scatter is likely caused by the combined effect of cold-mode gas accretion and merger-induced starbursts, with the latter more predominant in the dwarf mass regime of $M_\ast\lesssim10^9 M_\odot$., Comment: 86 pages, 75 figures, 3 tables, and 2 appendices, accepted to ApJ

We present the Super Eight galaxies - a set of very luminous, high-redshift ($7.1

We introduce the OSIRIS Lens-Amplified Survey (OLAS), a kinematic survey of gravitationally lensed galaxies at cosmic noon taken with Keck adaptive optics. In this paper we present spatially resolved spectroscopy and nebular emission kinematic maps for 17 star forming galaxies with stellar masses 8 < log($M_*$/$M_{\odot}$) < 9.8 and redshifts 1.2 < z < 2.3. OLAS is designed to probe the stellar mass ($M_*$) and specific star formation rate (sSFR) range where simulations suggest that stellar feedback is most effective at driving gaseous outflows that create galaxy-wide potential fluctuations which can generate dark matter cores. We compare our kinematic data with the trend between sSFR, $M_*$ and H$\alpha$ velocity dispersion, $\sigma$, from the Feedback In Realistic Environments (FIRE) simulations. Our observations reveal a correlation between sSFR and sigma at fixed $M_*$ that is similar to the trend predicted by simulations: feedback from star formation drives star-forming gas and newly formed stars into more dispersion dominated orbits. The observed magnitude of this effect is in good agreement with the FIRE simulations, in which feedback alters the central density profiles of low mass galaxies, converting dark matter cusps into cores over time. Our data support the scenario that stellar feedback drives gaseous outflows and potential fluctuations, which in turn drive dark matter core formation in dwarf galaxies., Comment: 9 pages (5 figures) with 9 page appendix (17 figures). Accepted to ApJ

We report the first sub-kiloparsec spatial resolution measurements of strongly inverted gas-phase metallicity gradients in two dwarf galaxies at $z$$\sim$2. The galaxies have stellar masses $\sim$$10^9M_\odot$, specific star-formation rate $\sim$20 Gyr$^{-1}$, and global metallicity $12+\log({\rm O/H})\sim8.1$ (1/4 solar), assuming the Maiolino et al. (2008) strong line calibrations of OIII/Hb and OII/Hb. Their metallicity radial gradients are measured to be highly inverted, i.e., 0.122$\pm$0.008 and 0.111$\pm$0.017 dex/kpc, which is hitherto unseen at such small masses in similar redshift ranges. From the Hubble Space Telescope observations of the source nebular emission and stellar continuum, we present the 2-dimensional spatial maps of star-formation rate surface density, stellar population age, and gas fraction, which show that our galaxies are currently undergoing rapid mass assembly via disk inside-out growth. More importantly, using a simple chemical evolution model, we find that the gas fractions for different metallicity regions cannot be explained by pure gas accretion. Our spatially resolved analysis based on a more advanced gas regulator model results in a spatial map of net gaseous outflows, triggered by active central starbursts, that potentially play a significant role in shaping the spatial distribution of metallicity by effectively transporting stellar nucleosynthesis yields outwards. The relation between wind mass loading factors and stellar surface densities measured in different regions of our galaxies shows that a single type of wind mechanism, driven by either energy or momentum conservation, cannot explain the entire galaxy. These sources present a unique constraint on the effects of gas flows on the early phase of disk growth from the perspective of spatially resolved chemical evolution within individual systems., Comment: 20 pages, 13 figures, 3 tables, accepted to ApJ. The accepted version includes a detailed description of extracting and fitting grism 1D/2D spectra (Appendix A) and a comparative study of deriving metallicity gradients using different strong line calibrations (Appendix C)

We present a gravitational lensing model of MACS J1149.5+2223 using ultra-deep Hubble Frontier Fields imaging data and spectroscopic redshifts from HST grism and VLT/MUSE spectroscopic data. We create total mass maps using 38 multiple images (13 sources) and 608 weak lensing galaxies, as well as 100 multiple images of 31 star-forming regions in the galaxy that hosts Supernova Refsdal. We find good agreement with a range of recent models within the HST field of view. We present a map of the ratio of projected stellar mass to total mass ($f_{\star}$), and find that the stellar mass fraction for this cluster peaks on the primary BCG. Averaging within a radius of 0.3 Mpc, we obtain a value of $\langle f_{\star} \rangle = 0.012^{+0.004}_{-0.003}$, consistent with other recent results for this ratio in cluster environments, though with a large global error (up to $\delta f_{\star} = 0.005$) primarily due to the choice of an IMF. We compare values of $f_{\star}$ and measures of star formation efficiency for this cluster to other Hubble Frontier Fields clusters studied in the literature, finding that MACS1149 has a higher stellar mass fraction than these other clusters, but a star formation efficiency typical of massive clusters., Comment: 15 pages, 6 figures, published in ApJ May 23, 2018

Galaxy-cluster gravitational lenses can magnify background galaxies by a total factor of up to ~50. Here we report an image of an individual star at redshift z=1.49 (dubbed "MACS J1149 Lensed Star 1 (LS1)") magnified by >2000. A separate image, detected briefly 0.26 arcseconds from LS1, is likely a counterimage of the first star demagnified for multiple years by a >~3 solar-mass object in the cluster. For reasonable assumptions about the lensing system, microlensing fluctuations in the stars' light curves can yield evidence about the mass function of intracluster stars and compact objects, including binary fractions and specific stellar evolution and supernova models. Dark-matter subhalos or massive compact objects may help to account for the two images' long-term brightness ratio., Comment: Accepted by Nature Astronomy on February 23, 2018

A galaxy cluster acts as a cosmic telescope over background galaxies but also as a cosmic microscope of the lens imperfections. The diverging magnification of lensing caustics enhances the microlensing effect of substructure present within the lensing mass. Fine-scale structure can be accessed as a moving background source brightens and disappears when crossing these caustics. The recent recognition of a distant lensed star near the Einstein radius of the galaxy cluster MACSJ1149.5+2223 (Kelly et al. 2017) allows the rare opportunity to reach subsolar mass microlensing through a super-critical column of cluster matter. Here we compare these observations with high-resolution ray-tracing simulations that include stellar microlensing set by the observed intracluster starlight and also primordial black holes that may be responsible for the recently observed LIGO events. We explore different scenarios with microlenses from the intracluster medium and black holes, including primordial ones, and examine strategies to exploit these unique alignments. We find that the best constraints on the fraction of compact dark matter in the small-mass regime can be obtained in regions of the cluster where the intracluster medium plays a negligible role. This new lensing phenomenon should be widespread and can be detected within modest-redshift lensed galaxies so that the luminosity distance is not prohibitive for detecting individual magnified stars. Continuous {\it Hubble Space Telescope} monitoring of several such optimal arcs will be rewarded by an unprecedented mass spectrum of compact objects that can contribute to uncovering the nature of dark matter., Comment: 29 pages and 21 figures (including two movies). Matches version accepted in ApJ

Within one billion years of the Big Bang, intergalactic hydrogen was ionized by sources emitting ultraviolet and higher energy photons. This was the final phenomenon to globally affect all the baryons (visible matter) in the Universe. It is referred to as cosmic reionization and is an integral component of cosmology. It is broadly expected that intrinsically faint galaxies were the primary ionizing sources due to their abundance in this epoch. However, at the highest redshifts ($z>7.5$; lookback time 13.1 Gyr), all galaxies with spectroscopic confirmations to date are intrinsically bright and, therefore, not necessarily representative of the general population. Here, we report the unequivocal spectroscopic detection of a low luminosity galaxy at $z>7.5$. We detected the Lyman-$\alpha$ emission line at $\sim 10504$ {\AA} in two separate observations with MOSFIRE on the Keck I Telescope and independently with the Hubble Space Telescope's slit-less grism spectrograph, implying a source redshift of $z = 7.640 \pm 0.001$. The galaxy is gravitationally magnified by the massive galaxy cluster MACS J1423.8+2404 ($z = 0.545$), with an estimated intrinsic luminosity of $M_{AB} = -19.6 \pm 0.2$ mag and a stellar mass of $M_{\star} = 3.0^{+1.5}_{-0.8} \times 10^8$ solar masses. Both are an order of magnitude lower than the four other Lyman-$\alpha$ emitters currently known at $z > 7.5$, making it probably the most distant representative source of reionization found to date.

Strongly lensed active galactic nuclei (AGN) provide a unique opportunity to make progress in the study of the evolution of the correlation between the mass of supermassive black holes ($\mathcal M_{BH}$) and their host galaxy luminosity ($L_{host}$). We demonstrate the power of lensing by analyzing two systems for which state-of-the-art lens modelling techniques have been applied to Hubble Space Telescope imaging data. We use i) the reconstructed images to infer the total and bulge luminosity of the host and ii) published broad-line spectroscopy to estimate $\mathcal M_{BH}$ using the so-called virial method. We then enlarge our sample with new calibration of previously published measurements to study the evolution of the correlation out to z~4.5. Consistent with previous work, we find that without taking into account passive luminosity evolution, the data points lie on the local relation. Once passive luminosity evolution is taken into account, we find that BHs in the more distant Universe reside in less luminous galaxies than today. Fitting this offset as $\mathcal M_{BH}$/$L_{host}$ $\propto$ (1+z)$^{\gamma}$, and taking into account selection effects, we obtain $\gamma$ = 0.6 $\pm$ 0.1 and 0.8$\pm$ 0.1 for the case of $\mathcal M_{BH}$-$L_{bulge}$ and $\mathcal M_{BH}$-$L_{total}$, respectively. To test for systematic uncertainties and selection effects we also consider a reduced sample that is homogeneous in data quality. We find consistent results but with considerably larger uncertainty due to the more limited sample size and redshift coverage ($\gamma$ = 0.7 $\pm$ 0.4 and 0.2$\pm$ 0.5 for $\mathcal M_{BH}$-$L_{bulge}$ and $\mathcal M_{BH}$-$L_{total}$, respectively), highlighting the need to gather more high-quality data for high-redshift lensed quasar hosts. Our result is consistent with a scenario where the growth of the black hole predates that of the host galaxy., Comment: 16 pages, 8 figures, 4 tables, Revised version after submitted to MNRAS

The CIII] and CIV rest-frame UV emission lines are powerful probes of the ionizations states of galaxies. They have furthermore been suggested as alternatives for spectroscopic redshift confirmation of objects at the epoch of reionization ($z>6$), where the most frequently used redshift indicator, Ly$\alpha$, is attenuated by the high fraction of neutral hydrogen in the inter-galactic medium. However, currently only very few confirmations of carbon UV lines at these high redshifts exist, making it challenging to quantify these claims. Here, we present the detection of CIV$\lambda\lambda$1548,1551\AA\ in \HST\ slitless grism spectroscopy obtained by GLASS of a Ly$\alpha$ emitter at $z=6.11$ multiply imaged by the massive foreground galaxy cluster RXJ2248. The CIV emission is detected at the 3--5$\sigma$ level in two images of the source, with marginal detection in two other images. We do not detect significant CIII]$\lambda\lambda$1907,1909\AA\ emission implying an equivalent width EW$_\textrm{CIII]}<20$\AA\ (1$\sigma$) and $\textrm{CIV/CIII}>0.7$ (2$\sigma$). Combined with limits on the rest-frame UV flux from the HeII$\lambda$1640\AA\ emission line and the OIII]$\lambda\lambda$1661,1666\AA\ doublet, we put constraints on the metallicity and the ionization state of the galaxy. The estimated line ratios and equivalent widths do not support a scenario where an AGN is responsible for ionizing the carbon atoms. SED fits including nebular emission lines imply a source with a mass of log(M/M$_\odot)\sim9$, SFR of around 10M$_\odot$/yr, and a young stellar population $<50$Myr old. The source shows a stronger ionizing radiation field than objects with detected CIV emission at $z<2$ and adds to the growing sample of low-mass (log(M/M$_\odot)\lesssim9$) galaxies at the epoch of reionization with strong radiation fields from star formation., Comment: Update after replying to referee report from ApJ

We investigate the intra-cluster light (ICL) in the 6 Hubble Frontier Field clusters at $0.3150$kpc) lies in a younger/bluer stellar population ($\sim1$Gyr), a phenomenon not seen in local samples. We attribute this light to the higher fraction of starforming/(post-)starburst galaxies in clusters at $z\sim0.5$. Ultimately, we find the ICL's total mass to be $\log M_{\rm *}^{\rm ICL}/M_\odot\sim11$-12, constituting 5%-20% of the clusters' total stellar mass, or about a half of the value at $z\sim0$. The above implies distinct formation histories for the ICL and BCGs/other massive cluster galaxies; i.e. the ICL at this epoch is still being constructed rapidly ($\sim40M_\odot$yr$^{-1}$), while the BCGs have mostly completed their evolution. To be consistent with the ICL measurements of local massive clusters, such as the Virgo, our data suggest mass acquisition mainly from quiescent cluster galaxies is the principal source of ICL material in the subsequent $\sim$5 Gyr of cosmic time., Comment: Accepted for Publication in The Astrophysical Journal

(Abridged) We combine deep HST grism spectroscopy with a new Bayesian method to derive maps of gas-phase metallicity, nebular dust extinction, and star-formation rate for 10 star-forming galaxies at high redshift ($1.2

Exploiting the slitless spectroscopy taken as part of the Grism Lens-Amplified Survey from Space (GLASS), we present an extended analysis of the spatial distribution of star formation in 76 galaxies in 10 clusters at 0.3< z <0.7. We use 85 foreground and background galaxies in the same redshift range as a field sample. The samples are well matched in stellar mass (10^8-10^11 M_sun) and star formation rate (0.5-50 M_sun/yr). We visually classify galaxies in terms of broad-band morphology, Halpha morphology and likely physical process acting on the galaxy. Most Halpha emitters have a spiral morphology (41+/-8% in clusters, 51+/-8% in the field), followed by mergers/interactions (28+/-8%, 31+/-7%, respectively) and early-type galaxies (remarkably as high as 29+/-8% in clusters and 15+/-6% in the field). A diversity of Halpha morphologies is detected, suggesting a diversity of physical processes. In clusters, 30+/-8% of the galaxies present a regular morphology, mostly consistent with star formation diffused uniformly across the stellar population (mostly in the disk component, when present). The second most common morphology (28+/-8%) is asymmetric/jellyfish, consistent with ram pressure stripping or other non-gravitational processes in 18+/-8% of the cases. Ram pressure stripping appears significantly less prominent in the field (2+/-2%), where the most common morphology/mechanism appears to be consistent with minor gas rich mergers or clump accretion. This work demonstrates that while environment specific mechanisms affect galaxy evolution at this redshift, they are diverse and their effects subtle. A full understanding of this complexity requires larger samples and detailed and spatially resolved physical models., Comment: ApJ in press (22 pages, 21 figures)

We present the first results of the KMOS Lens-Amplified Spectroscopic Survey (KLASS), a new ESO Very Large Telescope (VLT) large program, doing multi-object integral field spectroscopy of galaxies gravitationally lensed behind seven galaxy clusters selected from the HST Grism Lens-Amplified Survey from Space (GLASS). Using the power of the cluster magnification we are able to reveal the kinematic structure of 25 galaxies at $0.7 \lesssim z \lesssim 2.3$, in four cluster fields, with stellar masses $8 \lesssim \log{(M_\star/M_\odot)} \lesssim 11$. This sample includes 5 sources at $z>1$ with lower stellar masses than in any previous kinematic IFU surveys. Our sample displays a diversity in kinematic structure over this mass and redshift range. The majority of our kinematically resolved sample is rotationally supported, but with a lower ratio of rotational velocity to velocity dispersion than in the local universe, indicating the fraction of dynamically hot disks changes with cosmic time. We find no galaxies with stellar mass $<3 \times 10^9 M_\odot$ in our sample display regular ordered rotation. Using the enhanced spatial resolution from lensing, we resolve a lower number of dispersion dominated systems compared to field surveys, competitive with findings from surveys using adaptive optics. We find that the KMOS IFUs recover emission line flux from HST grism-selected objects more faithfully than slit spectrographs. With artificial slits we estimate slit spectrographs miss on average 60% of the total flux of emission lines, which decreases rapidly if the emission line is spatially offset from the continuum., Comment: Accepted for publication in ApJ

We derive a free-form mass distribution for the unrelaxed cluster A370 (z=0.375), using the latest Hubble Frontier Fields images and GLASS spectroscopy. Starting from a reliable set of 10 multiply lensed systems we produce a free-form lens model that identifies ~ 80 multiple-images. Good consistency is found between models using independent subsamples of these lensed systems, with detailed agreement for the well resolved arcs. The mass distribution has two very similar concentrations centred on the two prominent Brightest Cluster Galaxies (or BCGs), with mass profiles that are accurately constrained by a uniquely useful system of long radially lensed images centred on both BCGs. We show that the lensing mass profiles of these BCGs are mainly accounted for by their stellar mass profiles, with a modest contribution from dark matter within r<100 kpc of each BCG. This conclusion may favour a cooled cluster gas origin for BCGs, rather than via mergers of normal galaxies for which dark matter should dominate over stars. Growth via merging between BCGs is, however, consistent with this finding, so that stars still dominate over dark matter ., Comment: 19 pages, 11 figures. Submitted to MNRAS

Using the deepest data yet obtained, we find no evidence preferring compaction-triggered quenching---where rapid increases in galaxy density truncate star formation---over a null hypothesis in which galaxies age at constant surface density ($\Sigma_e\equiv M_*/2\pi r_{e}^{2}$). Results from two fully empirical analyses and one quenching-free model calculation support this claim at all $z\leq3$: (1) Qualitatively, galaxies' mean $U-V$ colors at $6.5\lesssim\log\Sigma_e/{\rm M_\odot}\,{\rm kpc}^{-2}\lesssim10$ have reddened at rates/times correlated with $\Sigma_e$, implying that there is no density threshold at which galaxies turn red but that $\Sigma_e$ sets the pace of maturation; (2) Quantitatively, the abundance of $\log M_*/{\rm M_\odot}\geq9.4$ red galaxies never exceeds that of the total population a quenching time earlier at any $\Sigma_e$, implying that galaxies need not transit from low to high densities before quenching; (3) Applying $d\log r_{e}/dt =1/2\,d\log M_*/dt$ to a suite of lognormal star formation histories reproduces the evolution of the size--mass relation at $\log M_*\geq10$. All results are consistent with evolutionary rates being set ab initio by global densities, with denser objects evolving faster than less-dense ones towards a terminal quiescence induced by gas depletion or other $\sim$Hubble-timescale phenomena. Unless stellar ages demand otherwise, observed $\Sigma_e$ thresholds need not bear any physical relation to quenching beyond this intrinsic density--formation epoch correlation, adding to Lilly & Carollo's arguments to that effect., Comment: 11 pages, 9 figures; Accepted to ApJ. This version replaces "How Strong is the Evidence for Density-Triggered Quenching?" (posted August 2016) to reflect revisions during refereeing. All results are unchanged, but the text now includes modeling, data, and appendices not present in the original manuscript. A movie of the size--mass evolution (Figure 4) is available upon request

Using deep Hubble Frontier Fields imaging and slitless spectroscopy from the Grism Lens-Amplified Survey from Space, we analyze 2200 cluster and 1748 field galaxies at $0.2\leq z\leq0.7$ to determine the impact of environment on galaxy size and structure at $\log M_*/M_\odot>7.8$, an unprecedented limit at these redshifts. Based on simple assumptions-$r_e=f(M_*)$-we find no significant differences in half-light radii ($r_e$) between equal-mass cluster or field systems. More complex analyses-$r_e=f(M_*,U-V,n,z,\Sigma$)-reveal local density $(\Sigma$) to induce only a $7\% \pm 3\%$ ($95\%$ confidence) reduction in $r_e$ beyond what can be accounted for by $U-V$ color, Sersic index ($n$), and redshift ($z$) effects.Almost any size difference between galaxies in high- and low-density regions is thus attributable to their different distributions in properties other than environment. Indeed, we find a clear color-$r_e$ correlation in low-mass passive cluster galaxies ($\log M_*/M_\odot<9.8$) such that bluer systems have larger radii, with the bluest having sizes consistent with equal-mass star-forming galaxies. We take this as evidence that large-$r_e$ low-mass passive cluster galaxies are recently acquired systems that have been environmentally quenched without significant structural transformation (e.g., by ram pressure stripping or starvation).Conversely, $\sim20\%$ of small-$r_e$ low-mass passive cluster galaxies appear to have been in place since $z\sim3$. Given the consistency of the small-$r_e$ galaxies' stellar surface densities (and even colors) with those of systems more than ten times as massive, our findings suggest that clusters mark places where galaxy evolution is accelerated for an ancient base population spanning most masses, with late-time additions quenched by environment-specific mechanisms are mainly restricted to the lowest masses., Comment: The accepted version. The catalog is available through the GLASS web page (http://glass.astro.ucla.edu), or https://www.astr.tohoku.ac.jp/~mtakahiro/Publication/Morishita17/

We report the detection of Ly$\alpha$ emission at $\sim9538$\AA{} in the Keck/DEIMOS and \HST WFC3 G102 grism data from a triply-imaged galaxy at $z=6.846\pm0.001$ behind galaxy cluster MACS J2129.4$-$0741. Combining the emission line wavelength with broadband photometry, line ratio upper limits, and lens modeling, we rule out the scenario that this emission line is \oii at $z=1.57$. After accounting for magnification, we calculate the weighted average of the intrinsic Ly$\alpha$ luminosity to be $\sim1.3\times10^{42}~\mathrm{erg}~\mathrm{s}^{-1}$ and Ly$\alpha$ equivalent width to be $74\pm15$\AA{}. Its intrinsic UV absolute magnitude at 1600\AA{} is $-18.6\pm0.2$ mag and stellar mass $(1.5\pm0.3)\times10^{7}~M_{\odot}$, making it one of the faintest (intrinsic $L_{UV}\sim0.14~L_{UV}^*$) galaxies with Ly$\alpha$ detection at $z\sim7$ to date. Its stellar mass is in the typical range for the galaxies thought to dominate the reionization photon budget at $z\gtrsim7$; the inferred Ly$\alpha$ escape fraction is high ($\gtrsim 10$\%), which could be common for sub-$L^*$ $z\gtrsim7$ galaxies with Ly$\alpha$ emission. This galaxy offers a glimpse of the galaxy population that is thought to drive reionization, and it shows that gravitational lensing is an important avenue to probe the sub-$L^*$ galaxy population., Comment: Accepted by ApJ Letters

To study the accretion phase for local massive galaxies, we search accreting satellites around a massive compact galaxy (M_*~3.9x10^10Msun), spectroscopically confirmed (z_spec-1.9213) in the eXtreme Deep Field, which has been originally reported in Szomoru et al. We detect 1369 satellite candidates within the projected virial radius (rvir~300 kpc) of the compact galaxy in the all-combined ACS image with 5sigma-limiting magnitude of mACS~30.6 ABmag, which corresponds to ~1.6x10^7M_sun at the redshift. The photometric redshift measured with 12 multi-band images confirms 34 satellites out of the candidates. Most of the satellites are found to have the rest-frame colors consistent with star forming galaxies. We investigate the relation between stellar mass and star formation rate (the star formation main sequence), and find the steeper slope at the low-mass end (<10^8M_sun), while more massive satellites are consistently on the sequence reported in previous studies. Within the uncertainties of star formation and photometric redshift, we conjecture possible scenarios for the compact galaxy which evolves to a local massive galaxy by way of significant size and mass growth. While merging of the existing total stellar mass of the satellites is not enough to explain the mass growth predicted by observations and simulations, the contribution by in-situ star formation in the satellites would compensate the deficit. Provided that most satellites keep the observed in-situ star formation and then quench before they accrete by, e.g., environmental quenching, the compact galaxy would become a massive early-type galaxy consistent with the local size-mass relation., Comment: 9 pages, 5 figures, accepted for publication in ApJ

Using the HST/WFC3 and ACS multi-band imaging data taken in CANDELS and 3D-HST, we study the general properties and the diversity of the progenitors of the Milky Way (MWs) and local massive galaxy (MGs) at 0.5 < z < 3.0, based on a constant cumulative number density analysis. After careful data reduction and stacking analysis, we conduct a radially resolved pixel SED fitting to obtain the radial distributions of the stellar mass and rest-frame colors. The stellar mass of MWs increases in self-similar way, irrespective of the radial distance, while that of MGs grows in inside-out way where they obtain ~ 75% of the total mass at outer (> 2.5 kpc) radius since z ~ 2. Although the radial mass profiles evolve in distinct ways, the formation and quenching of the central dense region (or bulge) ahead of the outer disk formation are found to be common for both systems. The sudden reddening of bulge at z ~ 1.6 and z ~ 2.4 for MWs and MGs, respectively, suggests the formation of bulge and would give a clue to the different gas accretion histories and quenching. A new approach to evaluate the morphological diversity is conducted by using the average surface density profile and its dispersion. The variety of the radial mass profiles for MGs peaks at higher redshift (z > 2.8), and then rapidly converges to more uniform shape at z < 1.5, while that for MWs remains in the outer region over the redshift. Compared with the observed star formation rates and color profiles, the evolution of variety is consistently explained by the star formation activities., Comment: Accepted for publication in The Astrophysical Journal

We analyze the recent released HST/WFC3 IR images in the GOODS-N region to study the formation and evolution of Quiescent galaxies (QGs). After examining the reliability with artificial galaxies, we obtain the morphological parameters with S'ersic profile of 299 QGs and 1,083 star-forming galaxies (SFGs) at z ~ 0.5-3.0, finding the evolution of re and n of massive (M* > 10^10.5 Msun) QGs while weaker evolution of SFGs and less massive (M* < 10^10.5 Msun) QGs. The regression of the size evolution of massive QGs follows re \propto (1 + z)-{\alpha}re with {\alpha}re = 1.06 \pm 0.19 (a factor of ~ 2.2 increase from z ~ 2.5 to ~ 0.5), which is consistent with the general picture of the significant size growth. For the further understanding of the evolution scenario, we study the evolution of S'ersic index, n, and find that of massive QGs to significantly evolve as n \propto (1 + z)-{\alpha}n with {\alpha}n = 0.74 \pm 0.23 (n ~ 1 at z ~ 2.5 to n ~ 4 at z ~ 0.5), while those of the other populations are unchanged (n ~ 1) over the redshift range. The results in the present study are consistent with both of observation and numerical simulations, where gas-poor minor merger is believed to be the main evolution scenario. By taking account of the connection with less massive QGs and SFGs, we discuss the formation and evolution of the massive QGs over "Cosmic High Noon", or the peak of star-formation in the universe., Comment: 20 pages, 21 figures, ApJ, accepted