- ID:
- ivo://CDS.VizieR/J/MNRAS/442/946
- Title:
- z~5.7 C IV absorption systems
- Short Name:
- J/MNRAS/442/946
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Metal absorption systems are products of star formation. They are believed to be associated with massive star-forming galaxies, which have significantly enriched their surroundings. To test this idea with high column density CIV absorption systems at z~5.7, we study the projected distribution of galaxies and characterize the environment of CIV systems in two independent quasar lines of sight: J103027.01+052455.0 and J113717.73+354956.9. Using wide-field photometry (~80x60h^-1^ comoving Mpc), we select bright (M_UV(1350{AA})_<~-21.0mag) Lyman break galaxies (LBGs) at z~5.7 in a redshift slice {Delta}z~0.2 and we compare their projected distribution with z~5.7 narrow-band selected Lyman alpha emitters (LAEs, {Delta}z~0.08). We find that the CIV systems are located more than 10h^-1^ projected comoving Mpc from the main concentrations of LBGs and no candidate is closer than ~5h^-1^ projected comoving Mpc. In contrast, an excess of LAEs - lower mass galaxies - is found on scales of ~10h^-1^ comoving Mpc, suggesting that LAEs are the primary candidates for the source of the CIV systems. Furthermore, the closest object to the system in the field J1030+0524 is a faint LAE at a projected distance of 212h^-1^ physical kpc. However, this work cannot rule out undiscovered lower mass galaxies as the origin of these absorption systems. We conclude that, in contrast with lower redshift examples (z<~3.5), strong CIV absorption systems at z~5.7 trace low-to-intermediate density environments dominated by low-mass galaxies. Moreover, the excess of LAEs associated with high levels of ionizing flux agrees with the idea that faint galaxies dominate the ionizing photon budget at this redshift.
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Search Results
- ID:
- ivo://CDS.VizieR/J/ApJ/697/1842
- Title:
- zCOSMOS 10K sample group catalog to z=1
- Short Name:
- J/ApJ/697/1842
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a galaxy group catalog spanning the redshift range 0.1<~z<~1 in the ~1.7deg^2^ COSMOS field, based on the first ~10000 zCOSMOS spectra. The performance of both the Friends-of-Friends (FOF) and Voronoi-Delaunay method (VDM) approaches to group identification has been extensively explored and compared using realistic mock catalogs. We find that the performance improves substantially if groups are found by progressively optimizing the group-finding parameters for successively smaller groups, and that the highest fidelity catalog, in terms of completeness and purity, is obtained by combining the independently created FOF and VDM catalogs. The final completeness and purity of this catalog, both in terms of the groups and of individual members, compares favorably with recent results in the literature. The current group catalog contains 102 groups with N>=5 spectroscopically confirmed members, with a further ~700 groups with 2<=N<=4. Most of the groups can be assigned a velocity dispersion and a dark-matter mass derived from the mock catalogs, with quantifiable uncertainties. The fraction of zCOSMOS galaxies in groups is about 25% at low redshift and decreases toward ~15% at z~0.8. The zCOSMOS group catalog is broadly consistent with that expected from the semianalytic evolution model underlying the mock catalogs.
- ID:
- ivo://CDS.VizieR/J/ApJ/753/121
- Title:
- zCOSMOS 20k sample group catalog to z<~1.2
- Short Name:
- J/ApJ/753/121
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present an optical group catalog between 0.1<~z<~1 based on 16500 high-quality spectroscopic redshifts in the completed zCOSMOS-bright survey. The catalog published herein contains 1498 groups in total and 192 groups with more than five observed members. The catalog includes both group properties and the identification of the member galaxies. Based on mock catalogs, the completeness and purity of groups with three and more members should be both about 83% with respect to all groups that should have been detectable within the survey, and more than 75% of the groups should exhibit a one-to-one correspondence to the "real" groups. Particularly at high redshift, there are apparently more galaxies in groups in the COSMOS field than expected from mock catalogs. We detect clear evidence for the growth of cosmic structure over the last seven billion years in the sense that the fraction of galaxies that are found in groups (in volume-limited samples) increases significantly with cosmic time. In the second part of the paper, we develop a method for associating galaxies that only have photo-z to our spectroscopically identified groups. We show that this leads to improved definition of group centers, improved identification of the most massive galaxies in the groups, and improved identification of central and satellite galaxies, where we define the former to be galaxies at the minimum of the gravitational potential wells. Subsamples of centrals and satellites in the groups can be defined with purities up to 80%, while a straight binary classification of all group and non-group galaxies into centrals and satellites achieves purities of 85% and 75%, respectively, for the spectroscopic sample.
- ID:
- ivo://CDS.VizieR/J/AJ/151/120
- Title:
- z<1 3CR radio galaxies and quasars star formation
- Short Name:
- J/AJ/151/120
- Date:
- 16 Dec 2021 13:37:06
- Publisher:
- CDS
- Description:
- Using the Herschel Space Observatory we have observed a representative sample of 87 powerful 3CR sources at redshift z<1. The far-infrared (FIR, 70-500 {mu}m) photometry is combined with mid-infrared (MIR) photometry from the Wide-Field Infrared Survey Explorer and cataloged data to analyze the complete spectral energy distributions (SEDs) of each object from optical to radio wavelength. To disentangle the contributions of different components, the SEDs are fitted with a set of templates to derive the luminosities of host galaxy starlight, dust torus emission powered by active galactic nuclei (AGNs), and cool dust heated by stars. The level of emission from relativistic jets is also estimated to isolate the thermal host galaxy contribution. The new data are in line with the orientation-based unification of high-excitation radio-loud AGN, in that the dust torus becomes optically thin longwards of 30 {mu}m. The low-excitation radio galaxies and the MIR-weak sources represent an MIR- and FIR-faint AGN population that is different from the high-excitation MIR-bright objects; it remains an open question whether they are at a later evolutionary state or an intrinsically different population. The derived luminosities for host starlight and dust heated by star formation are converted to stellar masses and star-formation rates (SFR). The host-normalized SFR of the bulk of the 3CR sources is low when compared to other galaxy populations at the same epoch. Estimates of the dust mass yield a 1-100 times lower dust/stellar mass ratio than for the Milky Way, which indicates that these 3CR hosts have very low levels of interstellar matter and explains the low level of star formation. Less than 10% of the 3CR sources show levels of star formation above those of the main sequence of star-forming galaxies.
- ID:
- ivo://CDS.VizieR/J/ApJ/776/71
- Title:
- ZENS: galaxies in groups along the cosmic web. I.
- Short Name:
- J/ApJ/776/71
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The Zurich Environmental Study (ZENS) is based on a sample of ~1500 galaxy members of 141 groups in the mass range ~10^12.5-14.5^M_{sun}_ within the narrow redshift range 0.05<z<0.0585. ZENS adopts novel approaches, described here, to quantify four different galactic environments, namely: (1) the mass of the host group halo; (2) the projected halo-centric distance; (3) the rank of galaxies as central or satellites within their group halos; and (4) the filamentary large-scale structure density. No self-consistent identification of a central galaxy is found in ~40% of <10^13.5^M_{sun}_ groups, from which we estimate that ~15% of groups at these masses are dynamically unrelaxed systems. Central galaxies in relaxed and unrelaxed groups generally have similar properties, suggesting that centrals are regulated by their mass and not by their environment. Centrals in relaxed groups have, however, ~30% larger sizes than in unrelaxed groups, possibly due to accretion of small satellites in virialized group halos. At M>10^10^M_{sun}_, satellite galaxies in relaxed and unrelaxed groups have similar size, color, and (specific) star formation rate distributions; at lower galaxy masses, satellites are marginally redder in relaxed relative to unrelaxed groups, suggesting quenching of star formation in low-mass satellites by physical processes active in relaxed halos. Overall, relaxed and unrelaxed groups show similar stellar mass populations, likely indicating similar stellar mass conversion efficiencies.
4226. ZFIRE v1.0 data release
- ID:
- ivo://CDS.VizieR/J/ApJ/828/21
- Title:
- ZFIRE v1.0 data release
- Short Name:
- J/ApJ/828/21
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present an overview and the first data release of ZFIRE, a spectroscopic redshift survey of star-forming galaxies that utilizes the MOSFIRE instrument on Keck-I to study galaxy properties in rich environments at 1.5<z<2.5. ZFIRE measures accurate spectroscopic redshifts and basic galaxy properties derived from multiple emission lines. The galaxies are selected from a stellar mass limited sample based on deep near infrared imaging (K_AB_<25) and precise photometric redshifts from the ZFOURGE and UKIDSS surveys as well as grism redshifts from 3DHST. Between 2013 and 2015, ZFIRE has observed the COSMOS and UDS legacy fields over 13 nights and has obtained 211 galaxy redshifts over 1.57<z<2.66 from a combination of nebular emission lines (such as H{alpha}, [NII], H{beta}, [OII], [OIII], and [SII]) observed at 1-2{mu}m. Based on our medium-band near infrared photometry, we are able to spectrophotometrically flux calibrate our spectra to ~10% accuracy. ZFIRE reaches 5{sigma} emission line flux limits of ~3x10^-18^erg/s/cm^2^ with a resolving power of R=3500 and reaches masses down to ~10^9^M_{sun}_. We confirm that the primary input survey, ZFOURGE, has produced photometric redshifts for star-forming galaxies (including highly attenuated ones) accurate to {Delta}z/(1+z_spec_)=0.015 with 0.7% outliers. We measure a slight redshift bias of <0.001, and we note that the redshift bias tends to be larger at higher masses. We also examine the role of redshift on the derivation of rest-frame colors and stellar population parameters from SED fitting techniques. The ZFIRE survey extends spectroscopically confirmed z~2 samples across a richer range of environments, here we make available the first public release of the data for use by the community.
- ID:
- ivo://CDS.VizieR/J/ApJ/897/44
- Title:
- 120 3<=z<=5 galaxies candidates in CANDELS fields
- Short Name:
- J/ApJ/897/44
- Date:
- 11 Mar 2022
- Publisher:
- CDS
- Description:
- Using the CANDELS photometric catalogs for the Hubble Space Telescope ACS and WFC3, we identified massive evolved galaxies at 3<z<4.5 employing three different selection methods. We find the comoving number density of these objects to be ~2x10^-5^ and 8x10^-6^/Mpc^3^ after correction for completeness for two redshift bins centered at z=3.4, 4.7. We quantify a measure of how much confidence we should have for each candidate galaxy from different selections and what the conservative error estimates propagated into our selection are. Then we compare the evolution of the corresponding number densities and their stellar mass density with numerical simulations, semianalytical models, and previous observational estimates, which shows slight tension at higher redshifts as the models tend to underestimate the number and mass densities. By estimating the average halo masses of the candidates (M_h_~4.2, 1.9, and 1.3x1012M{sun} for redshift bins centered at z=3.4, 4.1, and 4.7), we find them to be consistent with halos that were efficient in turning baryons to stars, relatively immune to the feedback effects, and on the verge of transition into hot-mode accretion. This can suggest the relative cosmological starvation of the cold gas followed by an overconsumption phase in which the galaxy rapidly consumes the available cold gas as one of the possible drivers for the quenching of the massive evolved population at high redshift.
- ID:
- ivo://CDS.VizieR/J/ApJ/803/34
- Title:
- z~4-10 galaxies from HST legacy fields
- Short Name:
- J/ApJ/803/34
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The remarkable Hubble Space Telescope (HST) data sets from the CANDELS, HUDF09, HUDF12, ERS, and BoRG/HIPPIES programs have allowed us to map the evolution of the rest-frame UV luminosity function (LF) from z~10 to z~4. We develop new color criteria that more optimally utilize the full wavelength coverage from the optical, near-IR, and mid-IR observations over our search fields, while simultaneously minimizing the incompleteness and eliminating redshift gaps. We have identified 5859, 3001, 857, 481, 217, and 6 galaxy candidates at z~4, z~5, z~6, z~7, z~8, and z~10, respectively, from the ~1000arcmin^2^ area covered by these data sets. This sample of >10000 galaxy candidates at z>=4 is by far the largest assembled to date with HST. The selection of z~4-8 candidates over the five CANDELS fields allows us to assess the cosmic variance; the largest variations are at z>=7. Our new LF determinations at z~4 and z~5 span a 6 mag baseline and reach to -16 AB mag. These determinations agree well with previous estimates, but the larger samples and volumes probed here result in a more reliable sampling of >L_{star}_ galaxies and allow us to reassess the form of the UV LFs. Our new LF results strengthen our earlier findings to 3.4{sigma} significance for a steeper faint-end slope of the UV LF at z>4, with {alpha} evolving from {alpha}=-1.64+/-0.04 at z~4 to {alpha}=-2.06+/-0.13 at z~7 (and {alpha}=-2.02+/-0.23 at z~8), consistent with that expected from the evolution of the halo mass function. We find less evolution in the characteristic magnitude M^*^ from z~7 to z~4 the observed evolution in the LF is now largely represented by changes in {phi}_{star}_. No evidence for a non-Schechter-like form to the z~4-8 LFs is found. A simple conditional LF model based on halo growth and evolution in the M/L ratio ({alpha}(1+z}^-1.5^) of halos provides a good representation of the observed evolution.
- ID:
- ivo://CDS.VizieR/J/MNRAS/478/4293
- Title:
- 0.1<z<0.8 galaxies gas-phase metallicity grad.
- Short Name:
- J/MNRAS/478/4293
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Galaxies at low-redshift typically possess negative gas-phase metallicity gradients (centres more metal-rich than their outskirts). Whereas, it is not uncommon to observe positive metallicity gradients in higher-redshift galaxies (z<0.6). Bridging these epochs, we present gas-phase metallicity gradients of 84 star-forming galaxies between 0.08<z<0.84. Using the galaxies with reliably determined metallicity gradients, we measure the median metallicity gradient to be negative (-0.039^+0.007^_-0.009_dex/kpc). Underlying this, however, is significant scatter: (8+/-3)% [7] of galaxies have significantly positive metallicity gradients, (38+/-5)% [32] have significantly negative gradients, (31+/-5)% [26] have gradients consistent with being flat. (The remaining (23+/-5)% [19] have unreliable gradient estimates.) We notice a slight trend for a more negative metallicity gradient with both increasing stellar mass and increasing star formation rate (SFR). However, given the potential redshift and size selection effects, we do not consider these trends to be significant. Indeed, once we normalize the SFR relative to that of the main sequence, we do not observe any trend between the metallicity gradient and the normalized SFR. This is contrary to recent studies of galaxies at similar and higher redshifts. We do, however, identify a novel trend between the metallicity gradient of a galaxy and its size. Small galaxies (rd<3kpc) present a large spread in observed metallicity gradients (both negative and positive gradients). In contrast, we find no large galaxies (rd > 3 kpc) with positive metallicity gradients, and overall there is less scatter in the metallicity gradient amongst the large galaxies. These large (well-evolved) galaxies may be analogues of present-day galaxies, which also show a common negative metallicity gradient.
- ID:
- ivo://CDS.VizieR/J/MNRAS/366/144
- Title:
- 0.06<=z<=1.20 galaxies Tully-Fisher relation
- Short Name:
- J/MNRAS/366/144
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have carried out spectroscopic observations in four cluster fields using Subaru's FOCAS multislit spectrograph and obtained spectra for 103 bright disc field and cluster galaxies at 0.06<=z<=1.20. 77 of these show emission lines, and 33 provide reasonably secure determinations of the galaxies' rotation velocity. The rotation velocities, luminosities, colours and emission-line properties of these galaxies are used to study the possible effects of the cluster environment on the star formation history of the galaxies.
