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18101. z=3.1 LAEs morphological properties
ID:
ivo://CDS.VizieR/J/ApJ/743/9
Title:
z=3.1 LAEs morphological properties
Short Name:
J/ApJ/743/9
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present a morphological analysis of the rest-frame ultraviolet emission of 78 resolved, high signal-to-noise z~3.1 Ly{alpha} emitters (LAEs) in the Extended Chandra Deep Field-South. Using Hubble Space Telescope/Advanced Camera for Surveys V-band images taken as part of the Galaxy Evolution from Morphology and SEDs, Great Observatories Origins Deep Survey, and Hubble Ultra Deep Field surveys, we investigate both single-component and multi-component LAEs, and derive concentration indices, Sersic indices, ellipticities, and half-light radii for all resolved components and systems with a signal-to-noise >30. We show that, although the LAE population is heterogeneous in nature, most LAEs are highly concentrated, with a distribution of C values similar to that measured for field stars; this suggests that the diagnostic is a poor discriminator near the resolution limit. The LAEs also display a wide range of Sersic indices (0<n<12), similar to that seen for galaxies in the local neighborhood. However, the majority of LAEs have n<2, and a visual inspection of the images suggests that the small-n objects have extended or multimodal luminosity profiles, while the LAEs with n>2 have compact components surrounded by diffuse emission. Moreover, unlike nearby spiral galaxies, whose distribution of ellipticities is flat, the LAE ellipticity distribution peaks near 1-b/a~0.55. Thus, the population has more in common with z~3 Lyman-break galaxies than local star-forming objects.
18102. z-low satellite galaxies in COSMOS survey
ID:
ivo://CDS.VizieR/J/MNRAS/478/5336
Title:
z-low satellite galaxies in COSMOS survey
Short Name:
J/MNRAS/478/5336
Date:
10 Dec 2021 14:18:30
Publisher:
CDS
Description:
Faint dwarf satellite galaxies are important as tracers of small-scale structure, but remain poorly characterized outside the Local Group, due to the difficulty of identifying them consistently at larger distances. We review a recently proposed method for estimating the average satellite population around a given sample of nearby bright galaxies, using a combination of size and magnitude cuts (to select low-redshift dwarf galaxies preferentially) and clustering measurements (to estimate the fraction of true satellites in the cut sample). We test this method using the high-precision photometric redshift catalogue of the COSMOS survey, exploring the effect of specific cuts on the clustering signal. The most effective of the size-magnitude cuts considered recover the clustering signal around low-redshift primaries (z<0.15) with about two-thirds of the signal and 80 per cent of the signal-to-noise ratio obtainable using the full COSMOS photometric redshifts. These cuts are also fairly efficient, with more than one-third of the selected objects being clustered satellites. We conclude that structural selection represents a useful tool in characterizing dwarf populations to fainter magnitudes and/or over larger areas than are feasible with spectroscopic surveys. In reviewing the low-redshift content of the COSMOS field, we also note the existence of several dozen objects that appear resolved or partially resolved in the HST imaging, and are confirmed to be local (at distances of ~250Mpc or less) by their photometric or spectroscopic redshifts. This underlines the potential for future space-based surveys to reveal local populations of intrinsically faint galaxies through imaging alone.
18103. z~1 Ly{alpha} emitters. I. 135 candidates from GALEX
ID:
ivo://CDS.VizieR/J/ApJ/783/119
Title:
z~1 Ly{alpha} emitters. I. 135 candidates from GALEX
Short Name:
J/ApJ/783/119
Date:
21 Oct 2021
Publisher:
CDS
Description:
We construct a flux-limited sample of 135 candidate z~1 Ly{alpha} emitters (LAEs) from Galaxy Evolution Explorer (GALEX) grism data using a new data cube search method. These LAEs have luminosities comparable to those at high redshifts and lie within a 7Gyr gap present in existing LAE samples. We use archival and newly obtained optical spectra to verify the UV redshifts of these LAEs. We use the combination of the GALEX UV spectra, optical spectra, and X-ray imaging data to estimate the active galactic nucleus (AGN) fraction and its dependence on Ly{alpha} luminosity. We remove the AGNs and compute the luminosity function (LF) from 60 z~1 LAE galaxies. We find that the best-fit LF implies a luminosity density increase by a factor of ~1.5 from z~0.3 to z~1 and ~20 from z~1 to z~2. We find a z~1 volumetric Ly{alpha} escape fraction of 0.7%+/-0.4%.
18104. z=2.4 Ly{alpha} emitters in the 53W002 field
ID:
ivo://CDS.VizieR/J/ApJ/759/133
Title:
z=2.4 Ly{alpha} emitters in the 53W002 field
Short Name:
J/ApJ/759/133
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present the results of our wide-field narrowband imaging of the field around the radio galaxy 53W002 at z=2.390 with Subaru/Suprime-Cam. A custom-made filter, NB413, centered at 4140{AA} with a width of 83{AA} is used to observe the 31'x24' area around the radio galaxy. We detected 204 Ly{alpha} emitters (LAEs) at z=2.4 with a rest-frame equivalent width larger than 25{AA} to the depth of 26 AB mag (in NB413). The entire LAE population in the 53W002 field has an average number density and distributions of equivalent width and size that are similar to those of other fields at z~2. We identify a significant high-density region (53W002F-HDR) that spreads over {approx}5'x4' near 53W002, where the LAE number density is nearly four times as large as the average of the entire field. Using the probability distribution function of density fluctuation, we evaluate the rareness probability of 53W002F-HDR to be 0.9^+2.4^_-0.62_%, which corresponds to a moderately rich structure. No notable environmental dependency at the comoving scale of 10Mpc is found for the distributions of the Ly{alpha} equivalent width and luminosity in the field. We also detected four Ly{alpha} blobs, one of which is newly discovered. They are all located in the rims of high-density regions. The biased location and unique morphologies in Ly{alpha} suggest that galaxy interaction plays a key role in their formation.
18105. z~4-7 Lyman break galaxies in Hubble deep fields
ID:
ivo://CDS.VizieR/J/ApJ/821/123
Title:
z~4-7 Lyman break galaxies in Hubble deep fields
Short Name:
J/ApJ/821/123
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present clustering analysis results from 10381 Lyman break galaxies (LBGs) at z~4-7, identified in the Hubble legacy deep imaging and new complimentary large-area Subaru/Hyper Suprime-Cam data. We measure the angular correlation functions of these LBGs at z~4, 5, 6, and 7 and fit these measurements using halo occupation distribution (HOD) models that provide an estimate of halo masses, M_h_~(1-20)x10^11^M_{sun}_. Our Mh estimates agree with those obtained by previous clustering studies in a UV-magnitude versus Mh plane and allow us to calculate stellar-to-halo mass ratios (SHMRs) of LBGs. By comparison with the z~0 SHMR, we identify evolution of the SHMR from z~0 to z~4 and from z~4 to z~7 at the >98% confidence levels. The SHMR decreases by a factor of ~2 from z~0 to 4 and increases by a factor of ~4 from z~4 to 7 at the dark matter halo mass of M_h_~10^11^M_{sun}. We compare our SHMRs with results of a hydrodynamic simulation and a semianalytic model and find that these theoretical studies do not predict the SHMR increase from z~4 to 7. We obtain the baryon conversion efficiency (BCE) of LBGs at z~4 and find that the BCE increases with increasing dark matter halo mass. Finally, we compare our clustering+HOD estimates with results from abundance matching techniques and conclude that the Mh estimates of the clustering+HOD analyses agree with those of the simple abundance matching within a factor of 3, and that the agreement improves when using more sophisticated abundance matching techniques that include subhalos, incompleteness, and/or evolution in the star formation and stellar mass functions.
18106. Zn measurements in sub-DLAs and DLAs QSOs
ID:
ivo://CDS.VizieR/J/ApJ/661/88
Title:
Zn measurements in sub-DLAs and DLAs QSOs
Short Name:
J/ApJ/661/88
Date:
21 Oct 2021
Publisher:
CDS
Description:
Observations of low mean metallicity of damped Ly{alpha} (DLA) quasar absorbers at all redshifts studied appear to contradict the predictions for the global mean interstellar metallicity in galaxies from cosmic chemical evolution models. On the other hand, a number of metal-rich sub-DLA systems have been identified recently, and the fraction of metal-rich sub-DLAs appears to be considerably larger than that of metal-rich DLAs, especially at z<1.5. In view of this, here we investigate the evolution of metallicity in sub-DLAs. We find that the mean Zn metallicity of the observed sub-DLAs may be higher than that of the observed DLAs, especially at low redshifts, reaching a near-solar level at z<~1. This trend does not appear to be an artifact of sample selection, the use of Zn, the use of N_HI_ weighting, or observational sensitivity.
18107. ZOAG galaxies in 115{deg}<l<157{deg}
ID:
ivo://CDS.VizieR/J/A+AS/137/293
Title:
ZOAG galaxies in 115{deg}<l<157{deg}
Short Name:
J/A+AS/137/293
Date:
21 Oct 2021
Publisher:
CDS
Description:
A systematic search by microscope for non-stellar objects on 19 POSS II R film copies has led to the detection of 3455 objects. The vast majority are obscured galaxies, most of which are new. We present coordinates and optical diameters of these galaxy candidates, list coincidences with objects in optical and infrared catalogues.
18108. z<0.5 PG quasars IR energy distributions
ID:
ivo://CDS.VizieR/J/ApJ/854/158
Title:
z<0.5 PG quasars IR energy distributions
Short Name:
J/ApJ/854/158
Date:
21 Oct 2021
Publisher:
CDS
Description:
The interstellar medium is crucial to understanding the physics of active galaxies and the coevolution between supermassive black holes and their host galaxies. However, direct gas measurements are limited by sensitivity and other uncertainties. Dust provides an efficient indirect probe of the total gas. We apply this technique to a large sample of quasars, whose total gas content would be prohibitively expensive to measure. We present a comprehensive study of the full (1 to 500{mu}m) infrared spectral energy distributions of 87 redshift <0.5 quasars selected from the Palomar-Green sample, using photometric measurements from 2MASS, WISE, and Herschel, combined with Spitzer mid-infrared (5-40{mu}m) spectra. With a newly developed Bayesian Markov Chain Monte Carlo fitting method, we decompose various overlapping contributions to the integrated spectral energy distribution, including starlight, warm dust from the torus, and cooler dust on galaxy scales. This procedure yields a robust dust mass, which we use to infer the gas mass, using a gas-to-dust ratio constrained by the host galaxy stellar mass. Most (90%) quasar hosts have gas fractions similar to those of massive, star-forming galaxies, although a minority (10%) seem genuinely gas-deficient, resembling present-day massive early-type galaxies. This result indicates that "quasar mode" feedback does not occur or is ineffective in the host galaxies of low-redshift quasars. We also find that quasars can boost the interstellar radiation field and heat dust on galactic scales. This cautions against the common practice of using the far-infrared luminosity to estimate the host galaxy star formation rate.
18109. 0.02<z<1.4 post-starburst SDSS galaxies
ID:
ivo://CDS.VizieR/J/ApJ/833/19
Title:
0.02<z<1.4 post-starburst SDSS galaxies
Short Name:
J/ApJ/833/19
Date:
21 Oct 2021
Publisher:
CDS
Description:
Post-starburst galaxies are in the transitional stage between blue, star-forming galaxies and red, quiescent galaxies and therefore hold important clues for our understanding of galaxy evolution. In this paper, we systematically searched for and identified a large sample of post-starburst galaxies from the spectroscopic data set of the Sloan Digital Sky Survey (SDSS) Data Release 9. In total, we found more than 6000 objects with redshifts between z~0.05 and z~1.3, making this the largest sample of post-starburst galaxies in the literature. We calculated the luminosity function of the post-starburst galaxies using two uniformly selected subsamples: the SDSS main galaxy sample and the Baryon Oscillation Spectroscopic Survey CMASS sample. The luminosity functions are reasonably fit by half-Gaussian functions. The peak magnitudes shift as a function of redshift from M~-23.5 at z~0.8 to M~-20.3 at z~0.1. This is consistent with the downsizing trend, whereby more massive galaxies form earlier than low-mass galaxies. We compared the mass of the post-starburst stellar population found in our sample to the decline of the global star formation rate and found that only a small amount (~1%) of all star formation quenching in the redshift range z=0.2-0.7 results in post-starburst galaxies in the luminosity range our sample is sensitive to. Therefore, luminous post-starburst galaxies are not the place where most of the decline in the star formation rate of the universe is happening.
18110. z~3-6 protoclusters in the CFHTLS deep fields
ID:
ivo://CDS.VizieR/J/ApJ/826/114
Title:
z~3-6 protoclusters in the CFHTLS deep fields
Short Name:
J/ApJ/826/114
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present the discovery of three protoclusters at z~3-4 with spectroscopic confirmation in the Canada-France-Hawaii Telescope Legacy Survey Deep Fields. In these fields, we investigate the large-scale projected sky distribution of z~3-6 Lyman-break galaxies and identify 21 protocluster candidates from regions that are overdense at more than 4{sigma} overdensity significance. Based on cosmological simulations, it is expected that more than 76% of these candidates will evolve into a galaxy cluster of at least a halo mass of 10^14^ M_{sun}_ at z=0. We perform follow-up spectroscopy for eight of the candidates using Subaru/FOCAS, Keck II/DEIMOS, and Gemini-N/GMOS. In total we target 462 dropout candidates and obtain 138 spectroscopic redshifts. We confirm three real protoclusters at z=3-4 with more than five members spectroscopically identified and find one to be an incidental overdense region by mere chance alignment. The other four candidate regions at z~5-6 require more spectroscopic follow-up in order to be conclusive. A z=3.67 protocluster, which has 11 spectroscopically confirmed members, shows a remarkable core-like structure composed of a central small region (<0.5 physical Mpc) and an outskirts region (~1.0 physical Mpc). The Ly{alpha} equivalent widths of members of the protocluster are significantly smaller than those of field galaxies at the same redshift, while there is no difference in the UV luminosity distributions. These results imply that some environmental effects start operating as early as at z~4 along with the growth of the protocluster structure. This study provides an important benchmark for our analysis of protoclusters in the upcoming Subaru/HSC imaging survey and its spectroscopic follow-up with the Subaru/PFS that will detect thousands of protoclusters up to z~6.

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