- ID:
- ivo://CDS.VizieR/J/A+A/559/A2
- Title:
- Redshifts in the surroundings of MRC 0156-252
- Short Name:
- J/A+A/559/A2
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the spectroscopic confirmation of a structure of galaxies surrounding the radio galaxy MRC 0156-252 at z=2.02. The structure was initially discovered as an overdensity of both near-infrared selected z>1.6 and mid-infrared selected z>1.2 galaxy candidates. We used the VLT/FORS2 multi-object spectrograph to target ~80 high-redshift galaxy candidates, and obtain robust spectroscopic redshifts for more than half the targets. The majority of the confirmed sources are star-forming galaxies at z>1.5. In addition to the radio galaxy, two of its close-by companions (<6") also show AGN signatures. Ten sources, including the radio galaxy, lie within |z-2.020|<0.015 (i.e., velocity offsets <1500km/s) and within projected 2Mpc comoving of the radio galaxy. Additional evidence suggests not only that the galaxy structure associated with MRC 0156-252 is a forming galaxy cluster but also that this structure is most probably embedded in a larger-scale structure.
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- 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.
- 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.
- 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.
- ID:
- ivo://CDS.VizieR/J/ApJ/384/404
- Title:
- Redshifts of a nearby rich clusters of galaxies
- Short Name:
- J/ApJ/384/404
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- (Abstract of the paper) We have acquired redshifts for a complete sample of 351 Abell clusters with tenth-ranked galaxy magnitudes (m_10_) less than or equal to 16.5, including 115 entirely new cluster redshifts. The survey includes all such clusters which lie north of {delta}=-27deg30arcmin and is the largest magnitude-limited redshift survey of rich clusters to date. Analysis of the spatial distribution of these clusters reveals no clustering on scales larger than 75h^-1^Mpc; we do not detect the large supercluster complexes reported by Tully. The correlation length is 20.0(+/-4.3)h^-1^Mpc, consistent with the results from other surveys. The frequency of voids with radii of order 60h^-1^Mpc or less is consistent with the form and amplitude of the observed two-point correlation function. There is no significant difference between the clustering properties of RC = O and RC >= 1 clusters. A percolation analysis yields 23 superclusters, 17 of which are new. The superclusters are not significantly elongated in the radial direction; large-scale peculiar motions are of order 1000 km s^-1^ or less. Dramatically new constraints on the large-scale cluster distribution will require surveys an order of magnitude larger.
- ID:
- ivo://CDS.VizieR/J/ApJ/365/66
- Title:
- Redshifts of a sample of distant Abell clusters
- Short Name:
- J/ApJ/365/66
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have measured redshifts for a complete sample of 145 Abell clusters of galaxies. The sample covers a 561 square degree region at high Galactic latitude. The median redshift of the clusters in the sample is 0.16. For R >= 1 clusters the correlation length is r_0_ = 21 h^-1^ Mpc. The amplitude of the correlation function is a factor of 1.4 less than that obtained by Bahcall and Soneira, but the difference is within the 1 {sigma} uncertainties. In this sample we cannot detect clustering on scales >~ 70 h^-1^ Mpc. Although the maps of the cluster distribution in redshift space show a large void of diameter ~20,000 km s^-1^, frequent occurrence of such large empty regions is consistent with the smaller scale behaviour of the correlation function of the survey. Large-scale peculiar motions are <~1000 km s^-1^. This limit is inconsistent with the claim of detection by Bahcall, Soneira, and Burgett of ~2000 km/s peculiar motions. We suggest that the earlier result is affected by the Corona Borealis supercluster, which contributes more than a third of the excess pairs in the shallower survey.
- ID:
- ivo://CDS.VizieR/J/AJ/123/100
- Title:
- Redshifts of AWM and MKW poor clusters
- Short Name:
- J/AJ/123/100
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have measured 1365 redshifts to a limiting magnitude of R~15.5 in 15 AWM/MKW clusters and have collected another 203 from the literature in MKW 4s, MKW 2, and MKW 2s. In AWM 7 we have extended the redshift sample to R~18 in the cluster center. We have identified 704 cluster members in 17 clusters; 201 are newly identified. We summarize the kinematics and distributions of the cluster galaxies and provide an initial discussion of substructure, mass and luminosity segregation, spectral segregation, velocity-dispersion profiles, and the relation of the central galaxy to global cluster properties. We compute optical mass estimates, which we compare with X-ray mass determinations from the literature.
- ID:
- ivo://CDS.VizieR/J/A+A/427/397
- Title:
- Redshifts of 5 EDisCS galaxy clusters
- Short Name:
- J/A+A/427/397
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Spectroscopic observations are presented for objects in the fields of 4 galaxy clusters at z=0.7-0.8 (Cl 1040.7-1155 (Cl 1040), Cl 1054.4-1146 (Cl 1054-11), Cl 1054.7-1245 (Cl 1054-12), and Cl 1216.8-1201 (Cl 1216)) and in one cluster at z~0.5 (Cl 1232.5-1250 (Cl 1232)) of the ESO Distant Cluster Survey (EDisCS). We present tables of RA and DE positions for an equinox of 2000 (J2000, epoch 2001), I-band magnitudes for an aperture of radius 1 arcsecond, spectroscopic redshifts for objects in the fields of our 5 clusters, and membership and targeting flags to indicate whether the object is a cluster member and/or was targeted to be a cluster member respectively.
- ID:
- ivo://CDS.VizieR/J/A+A/409/439
- Title:
- Redshifts of 11 EIS clusters
- Short Name:
- J/A+A/409/439
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the results of carrying out multi-object spectroscopy in 10 EIS cluster fields. Based on the list of 345 galaxy redshifts we identify significant 3D-density enhancements. For 9 of the EIS clusters we identify significant 3D-concentrations corresponding to the originally detected cluster candidate. We find redshifts in the range 0.097<=z<=0.257 which is in good agreement with the matched filter estimate of z_MF_=0.2. We estimate velocity dispersions in the range 219-1160km/s for the confirmed clusters
- ID:
- ivo://CDS.VizieR/J/A+A/388/1
- Title:
- Redshifts of five EIS clusters
- Short Name:
- J/A+A/388/1
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report the results of the first multi-object spectroscopic observations at the Danish 1.54m telescope at La Silla, Chile. Observations of five cluster candidates from The ESO Imaging Survey Cluster Candidate Catalog are described. From these observations we confirm the reality of the five clusters with measured redshifts of 0.11<=z<=0.35. We estimate velocity dispersions in the range 294-621km/s indicating rather poor clusters. This, and the measured cluster redshifts are consistent with the results of the matched filter procedure applied to produce the Cluster Candidate Catalog.
