- ID:
- ivo://CDS.VizieR/J/A+A/596/A14
- Title:
- Group catalogues of the local universe
- Short Name:
- J/A+A/596/A14
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Friends-of-friends algorithms are a common tool to detect galaxy groups and clusters in large survey data. In order to be as precise as possible, they have to be carefully calibrated using mock catalogues. We create an accurate and robust description of the matter distribution in the local Universe using the most up-to-date available data. This will provide the input for a specific cosmological test planned as follow-up to this work, and will be useful for general extragalactic and cosmological research. We create a set of galaxy group catalogues based on the 2MRS (Huchra et al., 2012, Cat. J/ApJS/199/26) and SDSS DR12 galaxy samples using a friends-of-friends based group finder algorithm. The algorithm is carefully calibrated and optimised on a new set of wide-angle mock catalogues from the Millennium simulation, in order to provide accurate total mass estimates of the galaxy groups taking into account the relevant observational biases in 2MRS and SDSS. We provide four different catalogues: (i) a 2MRS based group catalogue; (ii) a SDSS DR12 based group catalogue reaching out to a redshift z=0.11 with stellar mass estimates for 70% of the galaxies; (iii) a catalogue providing additional fundamental plane distances for all groups of the SDSS catalogue that host elliptical galaxies; (iv) a catalogue of the mass distribution in the local Universe based on a combination of our 2MRS and SDSS catalogues. While motivated by a specific cosmological test, three of the four catalogues that we produced are well suited to act as reference databases for a variety of extragalactic and cosmological science cases. Our catalogue of fundamental plane distances for SDSS groups provides further added value to this paper.
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Search Results
- ID:
- ivo://CDS.VizieR/J/A+A/573/A111
- Title:
- Group-dominant elliptical galaxies CO spectra
- Short Name:
- J/A+A/573/A111
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present IRAM 30m telescope observations of the CO(1-0) and (2-1) lines in a sample of 11 group-dominant elliptical galaxies selected from the CLoGS nearby groups sample. Our observations confirm the presence of molecular gas in 4 of the 11 galaxies at >4{sigma} significance, and combining these with data from the literature we find a detection rate of 43+/-14%, significantly higher than for the wider population of elliptical galaxies, and comparable to the detection rate for nearby radio galaxies. Those group-dominant galaxies which are detected typically contain ~2x10^8^M_{sun}_ of molecular gas, and although most have low star formation rates (<1M_{sun}_/yr) they have short depletion times, indicating that the gas must be replenished on timescales 10^8^yr. Almost all of the galaxies contain active nuclei, and we note that while CO detections are more common in the most radio-loud galaxies, the mass of molecular gas required to power the active nuclei through accretion is small compared to the masses observed. We consider the possible origin mechanisms for the gas, through cooling of stellar ejecta within the galaxies, group-scale cooling flows, and gas-rich mergers, and find probable examples of each type within our sample, confirming that a variety of processes act to drive the build up of molecular gas in group-dominant ellipticals.
- ID:
- ivo://CDS.VizieR/J/MNRAS/494/2090
- Title:
- Group galaxies in ALFALFA survey
- Short Name:
- J/MNRAS/494/2090
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We estimate the HI mass function (HIMF) of galaxies in groups based on thousands of ALFALFA (Arecibo Legacy Fast ALFA survey) HI detections within the galaxy groups of four widely used SDSS (Sloan Digital Sky Survey) groups catalogues. Although differences between the catalogues mean that there is no one definitive group galaxy HIMF, in general we find that the low-mass slope is flat, in agreement with studies based on small samples of individual groups, and that the 'knee' mass is slightly higher than that of the global HIMF of the full ALFALFA sample. We find that the observed fraction of ALFALFA galaxies in groups is approximately 22 per cent. These group galaxies were removed from the full ALFALFA source catalogue to calculate the field HIMF using the remaining galaxies. Comparison between the field and group HIMFs reveals that group galaxies make only a small contribution to the global HIMF as most ALFALFA galaxies are in the field, but beyond the HIMF 'knee' group galaxies dominate. Finally we attempt to separate the group galaxy HIMF into bins of group halo mass, but find that too few low-mass galaxies are detected in the most massive groups to tightly constrain the slope, owing to the rarity of such groups in the nearby Universe where low-mass galaxies are detectable with existing HI surveys.
- ID:
- ivo://CDS.VizieR/J/ApJ/749/150
- Title:
- Group galaxies in the RCS
- Short Name:
- J/ApJ/749/150
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We study the evolution of the red-galaxy fraction (f_red_) in 905 galaxy groups with 0.15<=z<0.52. The galaxy groups are identified by the "probability friends-of-friends" algorithm from the first Red-Sequence Cluster Survey (RCS1) photometric-redshift sample. There is a high degree of uniformity in the properties of the red sequence of the group galaxies, indicating that the luminous red-sequence galaxies in the groups are already in place by z~0.5 and that they have a formation epoch of z>~2. In general, groups at lower redshifts exhibit larger f_red_ than those at higher redshifts, showing a group Butcher-Oemler effect. We investigate the evolution of f_red_ by examining its dependence on four parameters, one of which can be classified as intrinsic and three of which can be classified as environmental: galaxy stellar mass (M_*_), total group stellar mass (M_*,grp_, a proxy for group halo mass), normalized group-centric radius (r_grp_), and local galaxy density ({Sigma}_5_).
- ID:
- ivo://CDS.VizieR/J/MNRAS/407/2207
- Title:
- Group of early-type galaxies
- Short Name:
- J/MNRAS/407/2207
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The fundamental plane of early-type galaxies is a rather tight three-parameter correlation discovered more than 20yr ago. It has resisted both a global and precise physical interpretation despite a consequent number of works, observational, theoretical or using numerical simulations. It appears that its precise properties depend on the population of galaxies in study. Instead of selecting a priori these populations, we propose to objectively construct homologous populations from multivariate analyses. We have undertaken multivariate cluster and cladistic analyses of a sample of 56 low-redshift galaxy clusters containing 699 early-type galaxies, using four parameters: effective radius, velocity dispersion, surface brightness averaged over effective radius and Mg_2_ index.
- ID:
- ivo://CDS.VizieR/J/ApJ/833/194
- Title:
- Group of galaxies in gravitational lens fields
- Short Name:
- J/ApJ/833/194
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- With a large, unique spectroscopic survey in the fields of 28 galaxy-scale strong gravitational lenses, we identify groups of galaxies in the 26 adequately sampled fields. Using a group-finding algorithm, we find 210 groups with at least 5 member galaxies; the median number of members is 8. Our sample spans redshifts of 0.04<=z_grp_<=0.76 with a median of 0.31, including 174 groups with 0.1<z_grp_<0.6. The groups have radial velocity dispersions of 60<={sigma}_grp_<=1200km/s with a median of 350km/s. We also discover a supergroup in field B0712+472 at z=0.29 that consists of three main groups. We recover groups similar to ~85% of those previously reported in these fields within our redshift range of sensitivity and find 187 new groups with at least five members. The properties of our group catalog, specifically, (1) the distribution of {sigma}_grp_, (2) the fraction of all sample galaxies that are group members, and (3) the fraction of groups with significant substructure, are consistent with those for other catalogs. The distribution of group virial masses agrees well with theoretical expectations. Of the lens galaxies, 12 of 26 (46%) (B1422+231, B1600+434, B2114+022, FBQS J0951+2635, HE0435-1223, HST J14113+5211, MG0751+2716, MGJ1654+1346, PG 1115+080, Q ER 0047-2808, RXJ1131-1231, and WFI J2033-4723) are members of groups with at least five galaxies, and one more (B0712+472) belongs to an additional, visually identified group candidate. There are groups not associated with the lens that still are likely to affect the lens model; in six of 25 (24%) fields (excluding the supergroup), there is at least one massive ({sigma}_grp_>=500km/s) group or group candidate projected within 2' of the lens.
- ID:
- ivo://CDS.VizieR/J/A+A/479/927
- Title:
- Group of galaxies in SDSS 5
- Short Name:
- J/A+A/479/927
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We extract groups of galaxies from the SDSS Data Release 5 to study the supercluster-void network and environmental properties of groups therein. Groups of galaxies as density enhancements can be used to determine the luminosity density field of the supercluster-void network. We use a modified friends-of-friends (FoF) method with slightly variable linking lengths in transverse and radial directions to eliminate selection effects and to reliably find as many groups as possible. To determine the scaling of the linking length we calibrated group sizes and mean galaxy number densities within groups by shifting nearby groups to larger distances. Our final sample contains 17143 groups in the equatorial (E), and 33219 groups in the northern (N) part of the DR5 survey. The mean sizes and velocity dispersions of our groups practically do not change with their distance. This means that the selection effects have been properly taken into account when generating the group catalogue.
- ID:
- ivo://CDS.VizieR/J/A+A/381/420
- Title:
- Group of Galaxies in the SSRS2 catalog
- Short Name:
- J/A+A/381/420
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present an automated method to detect populations of groups in galaxy redshift catalogs. This method uses both analysis of the redshift distribution along lines of sight in fixed cells to detect elementary structures and a friend-of-friend algorithm to merge these elementary structures into physical structures. We apply this method to the SSRS2 galaxy redshift catalog (Southern Sky Redshift Survey, Da Costa et al., Cat. J/AJ/116/1). The groups detected with our method are similar to group catalogs detected with pure friend-of-friend algorithms.
5759. Group of quasars
- ID:
- ivo://CDS.VizieR/J/MNRAS/249/218
- Title:
- Group of quasars
- Short Name:
- J/MNRAS/249/218
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have found evidence for a large, elongated group of at least ten quasars with largest dimension ~100-200h-1Mpc at z~1.3, in the direction of ESO/SERC field 927, which has the field centre (1950) 10h40m00s, 05deg00'00". There are probably further members that have not yet been observed. The morphology of the group seems to be like a clump, but there might be some sub-grouping on scales ~20h-1Mpc. The group is similar in size and number of quasars to that found by Crampton, Cowley & Hartwick (1989). The fact that two such groups are now known is evidence that the distribution of quasars is not so simple as was previously thought: at large scales (>10h-1Mpc) the majority of quasars may be distributed uniformly and at random, but rare, large groups also occur. The groups may be large physical structures, but a strong association with the large structures of galaxies seems doubtful.
5760. Groups of Galaxies
- ID:
- ivo://CDS.VizieR/J/AJ/113/483
- Title:
- Groups of Galaxies
- Short Name:
- J/AJ/113/483
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We use a friends-of-friends algorithm to identify loose groups from the northern CfA2 survey covering the region 8h<={alpha}_(1950)_<=17h and 8.5{deg}<={delta}_(1950)_<=44.5{deg}. There are 406 groups; 149 of these contains five or more members within the survey. Geometric simulations guide our choice of the selection parameters; {delta}{rho}/{rho}=80 is the limiting density contrast and V0=350km/s is the fiducial velocity linking parameter. The geometric simulations are particularly important for evaluating the impact of large-scale structure (e.g., the Great Wall) on group selection. The physical parameters of this large sample are coincident with our earlier results [126 groups in Ramella et al. (1989ApJ...344...57R)]: the median velocity dispersion in 192 (156; 229)km/s and the median blue log(M/L) is 2.38 (2.20; 2.52). The mass-to-light ratio (M/L) is in units of Msun/Lsun for an assumed Hubble constant, H0=100km/s/Mpc. The numbers in parentheses are 99% confidence limits. This group catalog provides a substantially larger sample for statistical studies than has been previously available. For example, it provides a more substantial sample for estimation of the distribution of group velocity dispersions and of the group-group correlation function. (Copyright) 1997 American Astronomical Society.