Abstract
The first deep field images from the James Webb Space Telescope (JWST) of the galaxy cluster SMACS J0723.3-7327 reveal a wealth of new lensed images at uncharted infrared wavelengths, with ...unprecedented depth and resolution. Here we securely identify 14 new sets of multiply imaged galaxies totaling 42 images, adding to the five sets of bright and multiply imaged galaxies already known from Hubble Space Telescope data. We find examples of arcs crossing critical curves, allowing detailed community follow-up, such as JWST spectroscopy for precise redshift determinations, and measurements of the chemical abundances and of the detailed internal gas dynamics of very distant, young galaxies. One such arc contains a pair of compact knots that are magnified by a factor of hundreds, and features a microlensed transient. We also detect an Einstein cross candidate only visible thanks to JWST’s superb resolution. Our parametric lens model is available through the following link (
https://www.dropbox.com/sh/gwup2lvks0jsqe5/AAC2RRSKce0aX-lIFCc9vhBXa?dl=0
) and will be regularly updated using additional spectroscopic redshifts. The model is constrained by 16 of these sets of multiply imaged galaxies, three of which have spectroscopic redshifts, and reproduces the multiple images to better than an rms of 0.″5, allowing for accurate magnification estimates of high-redshift galaxies. The intracluster light extends beyond the cluster members, exhibiting large-scale features that suggest a significant past dynamical disturbance. This work represents a first taste of the enhanced power JWST will have for lensing-related science.
Abstract
We present results on the morphological and structural evolution of a total of 3956 galaxies observed with JWST at 1.5 <
z
< 6.5 in the JWST CEERS observations that overlap with the CANDELS ...EGS field. This is the biggest visually classified sample observed with JWST yet, ∼20 times larger than previous studies, and allows us to examine in detail how galaxy structure has changed over this critical epoch. All sources were classified by six individual classifiers using a simple classification scheme aimed at producing disk/spheroid/peculiar classifications, whereby we determine how the relative number of these morphologies has evolved since the Universe’s first billion years. Additionally, we explore structural and quantitative morphology measurements using
Morfometryka
, and show that galaxies with
M
*
> 10
9
M
⊙
at
z
> 3 are not dominated by irregular and peculiar structures, either visually or quantitatively, as previously thought. We find a strong dominance of morphologically selected disk galaxies up to
z
= 6 in this mass range. We also find that the stellar mass and star formation rate densities are dominated by disk galaxies up to
z
∼ 6, demonstrating that most stars in the Universe were likely formed in a disk galaxy. We compare our results to theory to show that the fraction of types we find is predicted by cosmological simulations, and that the Hubble Sequence was already in place as early as one billion years after the Big Bang. Additionally, we make our visual classifications public for the community.
We measure the sizes of 82 massive galaxies at image utilizing deep HST NICMOS data taken in the GOODS North and South fields. Our sample is almost an order of magnitude larger than previous studies ...at these redshifts, providing the first statistical study of massive galaxy sizes at image, confirming the extreme compactness of these systems. We split our sample into disk-like and spheroid-like galaxies based on their Sersic indices, and find that at a given stellar mass disk-like galaxies at image are a factor of 2.6 +/- 0.3 smaller than present-day equal-mass systems, and spheroid-like galaxies at the same redshifts are 4.3 +/- 0.7 smaller than comparatively massive elliptical galaxies today. At image our results are compatible with both a leveling off, or a mild evolution in size. Furthermore, the high density (image2 x 10 super(10 ) Mimage kpcimage) of massive galaxies at these redshifts, which are similar to present-day globular clusters, possibly makes any further evolution in sizes beyond image unlikely.
This paper begins a series in which we examine the structures of distant galaxies to directly determine the history of their formation modes. We start this series by examining the structures of ...zF850LP < 27 galaxies in the Hubble Ultra-Deep Field (UDF), the deepest high-resolution optical image taken to date. We investigate a few basic features of galaxy structure using this image. These include: (1) the agreement of visual eye-ball classifications and non-parametric quantitative (CAS, Gini/M20) methods; (2) how distant galaxy quantitative structures can vary as a function of rest-frame wavelength; and (3) the evolution of distant galaxy structures up to z∼ 3. One of our major conclusions is that the majority of galaxies with z850 < 27 are peculiar in appearance, and that galaxy assembly is rapidly occurring at these magnitudes, even up to the present time. We find a general agreement between galaxy classification by eye and through quantitative methods, as well as a general agreement between the CAS and the Gini/M20 parameters. We find that the Gini/M20 method appears to find a larger number of galaxy mergers than the CAS system, but contains a larger contamination from non-mergers. We furthermore calculate the merger rate of galaxies in the UDF up to z∼ 3, finding an increase with redshift as well as stellar mass, confirming previous work in the Hubble Deep Field. We find that massive galaxies with M* > 1010M⊙ undergo 4.3−0.8+0.8 major galaxy mergers at z < 3, with all of this merging occurring at z > 1.
We present an analysis of the growth of stellar mass with cosmic time partitioned according to galaxy morphology. Using a well-defined catalog of 2150 galaxies based, in part, on archival data in the ...Great Observatories Origins Deep Survey (GOODS) fields, we assign morphological types in three broad classes (ellipticals, spirals, peculiar/irregulars) to a limit of z sub(AB) = 22.5 and make the resulting catalog publicly available. Utilizing 893 spectroscopic redshifts, supplemented by 1013 determined photometrically, we combine optical photometry from the GOODS catalog and deep K sub(s)-band imaging to assign stellar masses to each galaxy in our sample. We find little evolution in the form of the galaxy stellar mass function from z 6 1 to z = 0, especially at the high-mass end where our results are most robust. Although the population of massive galaxies is relatively well established at z 6 1, its morphological mix continues to change, with an increasing proportion of early-type galaxies at later times. By constructing type-dependent stellar mass functions, we show that in each of three redshift intervals, E/S0 galaxies dominate the higher mass population, while spirals are favored at lower masses. This transition occurs at a stellar mass of (2-3) x 10 super(10) M sub( )at z 6 0.3 (similar to local studies), but there is evidence that the relevant mass scale moves to higher mass at earlier epochs. Such evolution may represent the morphological extension of the "downsizing" phenomenon, in which the most massive galaxies stop forming stars first, with lower mass galaxies becoming quiescent later. We infer that more massive galaxies evolve into spheroidal systems at earlier times, and that this morphological transformation may only be completed 1-2 Gyr after the galaxies emerge from their active star-forming phase. We discuss several lines of evidence suggesting that merging may play a key role in generating this pattern of evolution.
Abstract
We present the detection of 89 low surface brightness (LSB), and thus low stellar density galaxy candidates in the Perseus cluster core, of the kind named ‘ultra-diffuse galaxies’, with mean ...effective V-band surface brightnesses 24.8–27.1 mag arcsec−2, total V-band magnitudes −11.8 to −15.5 mag, and half-light radii 0.7–4.1 kpc. The candidates have been identified in a deep mosaic covering 0.3 deg2, based on wide-field imaging data obtained with the William Herschel Telescope. We find that the LSB galaxy population is depleted in the cluster centre and only very few LSB candidates have half-light radii larger than 3 kpc. This appears consistent with an estimate of their tidal radius, which does not reach beyond the stellar extent even if we assume a high dark matter content (M/L = 100). In fact, three of our candidates seem to be associated with tidal streams, which points to their current disruption. Given that published data on faint LSB candidates in the Coma cluster – with its comparable central density to Perseus – show the same dearth of large objects in the core region, we conclude that these cannot survive the strong tides in the centres of massive clusters.
We characterize the mass-dependent evolution of more than 8000 galaxies using spectroscopic redshifts from the DEEP2 Galaxy Redshift Survey in the range 0.4 < z < 1.4 and stellar masses calculated ...from K-band photometry obtained at Palomar Observatory. This sample spans more than 1.5 deg super(2) in four independent fields. Using rest-frame U - B color and O II equivalent widths, we distinguish star-forming from passive populations in order to explore the nature of "downsizing"--a pattern in which the sites of active star formation shift from high-mass galaxies at early times to lower mass systems at later epochs. We identify a mass limit, M sub(Q), above which star formation appears to be quenched and show that the physical mechanisms responsible for downsizing can thus be empirically quantified by charting the evolution in this threshold mass. We find that M sub(Q) decreases with time by a factor of 63 across our redshift range according to M sub(Q) 8(1 + z) super(3.5). To further constrain possible quenching mechanisms, we investigate how downsizing depends on local galaxy environment using the projected third-nearest-neighbor statistic D sub(p,3). For the majority of galaxies near the median density, there is no significant correlation between downsizing and environment. However, a trend is observed in the comparison between environments that are more than 3 times overdense or underdense relative to the median. Here, downsizing appears accelerated in overdense regions that host higher numbers of massive, early-type galaxies as compared to the underdense regions. Our results significantly constrain recent suggestions for the origin of downsizing and indicate that the process for quenching star formation must, primarily, be internally driven.
ABSTRACTThis paper begins a series in which we examine the structures of distant galaxies to directly determine the history of their formation modes. We start this series by examining the structures ...of zF850LP < 27 galaxies in the Hubble Ultra-Deep Field (UDF), the deepest high-resolution optical image taken to date. We investigate a few basic features of galaxy structure using this image. These include: (1) the agreement of visual eye-ball classifications and non-parametric quantitative (CAS, Gini/M20) methods; (2) how distant galaxy quantitative structures can vary as a function of rest-frame wavelength; and (3) the evolution of distant galaxy structures up to z similar to 3. One of our major conclusions is that the majority of galaxies with z850 < 27 are peculiar in appearance, and that galaxy assembly is rapidly occurring at these magnitudes, even up to the present time. We find a general agreement between galaxy classification by eye and through quantitative methods, as well as a general agreement between the CAS and the Gini/M20 parameters. We find that the Gini/M20 method appears to find a larger number of galaxy mergers than the CAS system, but contains a larger contamination from non-mergers. We furthermore calculate the merger rate of galaxies in the UDF up to z similar to 3, finding an increase with redshift as well as stellar mass, confirming previous work in the Hubble Deep Field. We find that massive galaxies with M* > 1010Modot undergo 4.3-0.8+0.8 major galaxy mergers at z < 3, with all of this merging occurring at z > 1.
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