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5541. Redshifts in X-ray-selected groups of galaxies
ID:
ivo://CDS.VizieR/J/ApJ/646/133
Title:
Redshifts in X-ray-selected groups of galaxies
Short Name:
J/ApJ/646/133
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present spectroscopic confirmation of nine moderate-redshift galaxy groups and poor clusters selected from the ROSAT Deep Cluster Survey. The groups span the redshift range and have between 4 and 20 confirmed members. The velocity dispersions of these groups range from ~125 to 650km/s. Similar to X-ray groups at low redshift, these systems contain a significant number of early-type galaxies. Therefore, the trend for X-ray-luminous groups to have high early-type fractions is already in place by at least z~0.5. In four of the nine groups, the X-ray emission is clearly peaked on the most luminous early-type galaxy in the group. However, in several cases the central galaxy is composed of multiple luminous nuclei, suggesting that the brightest group galaxy may still be undergoing major mergers. In at least three (and possibly five) of the groups in our sample, a dominant early-type galaxy is not found at the center of the group potential. This suggests that many of our groups are not dynamically evolved despite their high X-ray luminosities. While similar systems have been identified at low redshift, the X-ray luminosities of the intermediate-redshift examples are 13 orders of magnitude higher than those of their low-redshift counterparts. We suggest that this may be evidence for group downsizing: while massive groups are still in the process of collapsing and virializing at intermediate redshifts, only low-mass groups are in the process of forming at the present day.
5542. Redshifts in z~0.25 clusters
ID:
ivo://CDS.VizieR/J/A+A/486/9
Title:
Redshifts in z~0.25 clusters
Short Name:
J/A+A/486/9
Date:
21 Oct 2021
Publisher:
CDS
Description:
We investigate the relation between star-formation activity and environment in six intermediate redshift clusters (z~0.25) out to large clustercentric distances (~4R_vir_). For that, we conducted a panoramic spectroscopic campaign with MOSCA at the Calar Alto observatory. We acquired spectra of more than 500 objects. Approximately 150 of these spectra were of galaxies that are members of the clusters. Other ~150 are field galaxies or galaxies belonging to groups, serendipitously found during the investigation. The rest of the spectra did not met the quality criteria or were stars. The wavelength range allows us to quantify the star formation activity by using the [OII] and the H{alpha} lines. This activity is examined in terms of the large-scale environment expressed by the clustercentric distance of the galaxies as well as on local scales given by the spatial galaxy densities. The suppression of the star-formation activity is observed at large clustercentric distances and low projected densities. Galaxies with current star-formation show similar activity, regardless of the environment, Therefore, the decline of the star-formation activity inside the investigated clusters is driven mainly by the significant change in the fraction of active versus passive populations. This suggests that the suppression of the star-formation activity occurs on short timescales. We also detect a significant population of red star-forming galaxies whose colors are consistent with the red-sequence of passive galaxies. They appear to be in an intermediate evolutionary stage between active and passive types.
5543. Redshifts of ABCG209 galaxies
ID:
ivo://CDS.VizieR/J/A+A/397/431
Title:
Redshifts of ABCG209 galaxies
Short Name:
J/A+A/397/431
Date:
21 Oct 2021
Publisher:
CDS
Description:
We study the internal dynamics of the rich galaxy cluster ABGC 209 on the basis of new spectroscopic and photometric data. The distribution in redshift shows that ABCG 209 is a well isolated peak of 112 detected member galaxies at z=0.209, characterised by a high value of the line-of-sight velocity dispersion, {sigma}_v_=1250-1400km/s, on the whole observed area (1h^-1^Mpc from the cluster center), that leads to a virial mass of M=1.6-2.2x10^15^h^-1^M_{sun}_ within the virial radius, assuming the dynamical equilibrium. The data were collected at the ESO New Technology Telescope (NTT) with the ESO Multi Mode Instrument (EMMI) in October 2001.
5544. Redshifts of galaxies associated with X emission
ID:
ivo://CDS.VizieR/J/A+A/468/807
Title:
Redshifts of galaxies associated with X emission
Short Name:
J/A+A/468/807
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present the results of spectroscopic observations of galaxies associated with the diffuse X-ray emitting structure discovered by Zappacosta et al. (2002A&A...394....7Z). After measuring the redshifts of 161 galaxies, we confirm an overdensity of galaxies with projected dimensions of at least 2Mpc, determine its spectroscopic redshift in z=0.401+/-0.002, and show that it is spatially coincident with the diffuse X-ray emission. This confirms the original claim that this X-ray emission has an extragalactic nature and is due to the warm-hot intergalactic medium (WHIM). We used this value of the redshift to compute the temperature of the emitting gas. The resulting value depends on the metallicity that is assumed for the IGM, and is constrained to be between 0.3 and 0.6keV for metallicities between 0.05 and 0.3solar, in good agreement with the expectations from the WHIM.
5545. Redshifts of 1151 galaxies from SDSS
ID:
ivo://CDS.VizieR/J/ApJ/781/2
Title:
Redshifts of 1151 galaxies from SDSS
Short Name:
J/ApJ/781/2
Date:
21 Oct 2021
Publisher:
CDS
Description:
Lines of sight with multiple projected cluster-scale gravitational lenses have high total masses and complex lens plane interactions that can boost the area of magnification, or etendue, making detection of faint background sources more likely than elsewhere. To identify these new "compound" cosmic telescopes, we have found directions in the sky with the highest integrated mass densities, as traced by the projected concentrations of luminous red galaxies (LRGs). We use new galaxy spectroscopy to derive preliminary magnification maps for two such lines of sight with total mass exceeding ~3x10^15^M_{sun}_. From 1151 MMT Hectospec spectra of galaxies down to i_AB_=21.2, we identify two to three group- and cluster-scale halos in each beam. These are well traced by LRGs. The majority of the mass in beam J085007.6+360428 (0850) is contributed by Zwicky 1953, a massive cluster at z=0.3774, whereas beam J130657.5+463219 (1306) is composed of three halos with virial masses of 6x10^14^-2x10^15^M_{sun}_, one of which is A1682. The magnification maps derived from our mass models based on spectroscopy and Sloan Digital Sky Survey photometry alone display substantial etendue: the 68% confidence bands on the lens plane area with magnification exceeding 10 for a source plane of z_s_=10 are [1.2,3.8]arcmin^2^ for 0850 and [2.3,6.7]arcmin^2^ for 1306. In deep Subaru Suprime-Cam imaging of beam 0850, we serendipitously discover a candidate multiply imaged V-dropout source at z_phot_=5.03. The location of the candidate multiply imaged arcs is consistent with the critical curves for a source plane of z=5.03 predicted by our mass model. Incorporating the position of the candidate multiply imaged galaxy as a constraint on the critical curve location in 0850 narrows the 68% confidence band on the lens plane area with {mu}>10 and z_s_=10 to [1.8,4.2]arcmin^2^, an etendue range comparable to that of MACS 0717+3745 and El Gordo, two of the most powerful single cluster lenses known. The significant lensing power of our beams makes them powerful probes of reionization and galaxy formation in the early universe.
5546. Redshifts of galaxies in Abell 1351 field
ID:
ivo://CDS.VizieR/J/MNRAS/442/2216
Title:
Redshifts of galaxies in Abell 1351 field
Short Name:
J/MNRAS/442/2216
Date:
21 Oct 2021
Publisher:
CDS
Description:
We aim to review the internal structure and dynamics of the Abell 1351 cluster, shown to host a radio halo with a quite irregular shape. Our analysis is based on radial velocity data for 135 galaxies obtained at the Telescopio Nazionale Galileo. We combine galaxy velocities and positions to select 95 cluster galaxy members and analyse the internal dynamics of the whole cluster. We also examine X-ray data retrieved from Chandra and XMM archives. We measure the cluster redshift, <z>=0.325, the line-of-sight (LOS) velocity dispersion, {sigma}V~1500km/s, and the X-ray temperature, kT~9keV. From both X-ray and optical data independently, we estimate a large cluster mass, in the 1-4x10^15^h_70_^-1^M_{sun}_. We attribute the extremely high value of {sigma}V to the bimodality in the velocity distribution. We find evidence of a significant velocity gradient and optical 3D substructure. The X-ray analysis also shows many features in favour of a complex cluster structure, probably supporting an ongoing merger of substructures in Abell 1351. The observational scenario agrees with the presence of two main subclusters in the northern region, each with its brightest galaxy (BCG1 and BCG2), detected as the two most important X-ray substructures with a rest-frame LOS velocity difference of {Delta}V_rf_~2500km/s and probably being in large part aligned with the LOS. We conclude that Abell 1351 is a massive merging cluster. The details of the cluster structure allow us to interpret the quite asymmetric radio halo as a 'normal' halo plus a southern relic, strongly supporting a previous suggestion based only on inspection of radio and preliminary X-ray data.
5547. Redshifts of galaxies in 21 EIS cluster fields
ID:
ivo://CDS.VizieR/J/A+A/435/781
Title:
Redshifts of galaxies in 21 EIS cluster fields
Short Name:
J/A+A/435/781
Date:
21 Oct 2021
Publisher:
CDS
Description:
We have carried out an investigation of the properties of low redshift EIS clusters using both spectroscopy and imaging data. We present new redshifts for 738 galaxies in 21 ESO Imaging Survey (EIS) Cluster fields. We use the "gap"-technique to search for significant overdensities in redshift space and to identify groups/clusters of galaxies corresponding to the original EIS matched filter cluster candidates. In this way we spectroscopically confirm 20 of the 21 cluster candidates with a matched-filter estimated redshift z_MF_=0.2. We have now obtained spectroscopic redshifts for 34 EIS cluster candidates with z_MF_=0.2 (see also Hansen et al., 2002, Cat. <J/A+A/388/1>; Olsen et al., 2003, Cat. <J/A+A/409/439>. Of those we spectroscopically confirm 32 with redshifts ranging from z=0.064 to 0.283. We find that: 1) the velocity dispersions of the systems range from sigma_v_<=130km/s to sigma_v_=1200km/s, typical of galaxy groups to rich clusters; 2) richnesses corresponding to Abell classes R<=1; and 3) concentration indices ranging from C=0.2 to C=1.2. From the analysis of the colours of the galaxy populations we find that 53% of the spectroscopically confirmed systems have a "significant" red sequence. These systems are on average richer and have higher velocity dispersions. We find that the colour of the red sequence galaxies matches passive stellar evolution predictions.
5548. Redshifts of obscured AGN
ID:
ivo://CDS.VizieR/J/A+A/618/A66
Title:
Redshifts of obscured AGN
Short Name:
J/A+A/618/A66
Date:
21 Oct 2021
Publisher:
CDS
Description:
Redshifts are fundamental for our understanding of extragalactic X-ray sources. Ambiguous counterpart associations, expensive optical spectroscopy and/or multimission multiwavelength coverage to resolve degeneracies make estimation often difficult in practice. We attempt to constrain redshifts of obscured Active Galactic Nuclei (AGN) using only low-resolution X-ray spectra. Our XZ method fits AGN X-ray spectra with a moderately complex spectral model incorporating a corona, torus obscurer and warm mirror. Using the Bayesian X-ray Astronomy (BXA) package, we constrain redshift, column density, photon index and luminosity simultaneously. The redshift information primarily comes from absorption edges in Compton-thin AGN, and from the Fe K{alpha} fluorescent line in heavily obscured AGN. A new generic background fitting method allows us to extract more information from limited numbers of source counts. We derive redshift constraints for 74/321 hard-band detected sources in the Chandra deep field South. Comparing with spectroscopic redshifts, we find an outlier fraction of 8%, indicating that our model assumptions are valid. For three Chandra deep fields, we release our XZ redshift estimates. The independent XZ estimate is easy to apply and effective for a large fraction of obscured AGN in todays deep surveys without the need for any additional data. Comparing to different redshift estimation methods, XZ can resolve degeneracies in photometric redshifts, help to detect potential association problems and confirm uncertain single-line spectroscopic redshifts. With high spectral resolution and large collecting area, this technique will be highly effective for Athena/WFI observations.
5549. Redshift survey in 15 quasar fields
ID:
ivo://CDS.VizieR/J/MNRAS/367/1261
Title:
Redshift survey in 15 quasar fields
Short Name:
J/MNRAS/367/1261
Date:
21 Oct 2021
Publisher:
CDS
Description:
We investigate the relative distribution of the gaseous contents of the Universe (as traced by a sample of Ly{alpha} absorbers), and the luminous baryonic matter (as traced by a redshift survey of galaxies in the same volume searched for Ly{alpha} absorbers), along 16 lines of sight (LOS) between redshifts 0 and 1. Our galaxy redshift survey was made with the multi-object spectrograph on the Canada-France-Hawaii Telescope and, when combined with galaxies from the literature in the same LOS, gives us a galaxy sample of 636 objects. By combining this with an absorption-line sample of 406 absorbing systems drawn from published works, we are able to study the relationship between gas and galaxies over the latter half of the age of the Universe.
5550. Redshift survey in the field of A1689
ID:
ivo://CDS.VizieR/J/ApJ/665/921
Title:
Redshift survey in the field of A1689
Short Name:
J/ApJ/665/921
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present results of the HST Advanced Camera for Surveys spectroscopic ground-based redshift survey in the field of A1689. We measure 98 redshifts, increasing the number of spectroscopically confirmed objects sixfold. We present two spectra from this catalog of the Sextet Arcs, images that arise from a strongly lensed Lyman break galaxy (LBG) at a redshift of z=3.038. Gravitational lensing by the cluster magnifies its flux by a factor of ~16 and produces six separate images with a total r-band magnitude of r_625_=21.7. The two spectra, each of which represents emission from different regions of the LBG, show HI and interstellar metal absorption lines at the systemic redshift.