- ID:
- ivo://CDS.VizieR/J/MNRAS/465/2616
- Title:
- Galaxy cluster's rotation
- Short Name:
- J/MNRAS/465/2616
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We study the possible rotation of cluster galaxies, developing, testing, and applying a novel algorithm which identifies rotation, if such does exist, as well as its rotational centre, its axis orientation, rotational velocity amplitude, and, finally, the clockwise or counterclockwise direction of rotation on the plane of the sky. To validate our algorithms we construct realistic Monte Carlo mock rotating clusters and confirm that our method provides robust indications of rotation. We then apply our methodology on a sample of Abell clusters with z<=0.1 with member galaxies selected from the Sloan Digital Sky Survey DR10 spectroscopic data base. After excluding a number of substructured clusters, which could provide erroneous indications of rotation, and taking into account the expected fraction of misidentified coherent substructure velocities for rotation, provided by our Monte Carlo simulation analysis, we find that ~23 per cent of our clusters are rotating under a set of strict criteria. Loosening the strictness of the criteria, on the expense of introducing spurious rotation indications, we find this fraction increasing to ~28 per cent. We correlate our rotation indicators with the cluster dynamical state, provided either by their Bautz-Morgan type or by their X-ray isophotal shape and find for those clusters showing rotation within 1.5h^-1^_70_ Mpc that the significance of their rotation is related to the dynamically younger phases of cluster formation but after the initial anisotropic accretion and merging has been completed. Finally, finding rotational modes in galaxy clusters could lead to the necessity of correcting the dynamical cluster mass calculations.
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Search Results
- ID:
- ivo://CDS.VizieR/J/MNRAS/412/2498
- Title:
- Galaxy groups and clouds in the local universe
- Short Name:
- J/MNRAS/412/2498
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present an all-sky catalogue of 395 nearby galaxy groups revealed in the Local Supercluster and its surroundings. The groups and their associations are identified among 10914 galaxies at |b|>15{deg} with radial velocities V_LG_<3500km/s. Our group-finding algorithm requires the group members to be located inside their zero-velocity surface. Hereby, we assume that individual galaxy masses are proportional to their total K-band luminosities, M/L_K_=6M_{sun}_/L_{sun}_. The sample of our groups, where each group has n>=4 members, is characterized by the following medians: mean projected radius <R>=268kpc, radial velocity dispersion {sigma}_V_=74km/s, K-band luminosity L_K_=1.2x10^11^L_{sun}_, virial and projected masses M_vir_=2.4x10^12^ and M_p_=3.3x10^12^M_{sun}_, respectively. Accounting for measurement error reduces the median masses by 30 per cent. For 97 per cent of identified groups the crossing time does not exceed the cosmic time, 13.7Gyr, with the median at 3.8Gyr. We examine different properties of the groups, in particular of the known nearby groups and clusters in Virgo and Fornax. About a quarter of our groups can be classified as fossil groups where the dominant galaxy is at least 10 times brighter than the other group members.
- ID:
- ivo://CDS.VizieR/J/ApJS/167/1
- Title:
- Galaxy groups and clusters from SDSS
- Short Name:
- J/ApJS/167/1
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We identify galaxy groups and clusters in volume-limited samples of the Sloan Digital Sky Survey (SDSS) redshift survey, using a redshift-space friends-of-friends algorithm. We optimize the friends-of-friends linking lengths to recover galaxy systems that occupy the same dark matter halos, using a set of mock catalogs created by populating halos of N-body simulations with galaxies. Extensive tests with these mock catalogs show that no combination of perpendicular and line-of-sight linking lengths is able to yield groups and clusters that simultaneously recover the true halo multiplicity function, projected size distribution, and velocity dispersion. We adopt a linking length combination that yields, for galaxy groups with 10 or more members: a group multiplicity function that is unbiased with respect to the true halo multiplicity function; an unbiased median relation between the multiplicities of groups and their associated halos; a spurious group fraction of less than ~1%; a halo completeness of more than 97%; the correct projected size distribution as a function of multiplicity; and a velocity dispersion distribution that is ~20% too low at all multiplicities. These results hold over a range of mock catalogs that use different input recipes of populating halos with galaxies. We apply our group-finding algorithm to the SDSS data and obtain three group and cluster catalogs for three volume-limited samples that cover 3495.1deg^2^ on the sky, go out to redshifts of 0.1, 0.068, and 0.045, and contain 57138, 37820, and 18895 galaxies, respectively. We correct for incompleteness caused by fiber collisions and survey edges and obtain measurements of the group multiplicity function, with errors calculated from realistic mock catalogs. These multiplicity function measurements provide a key constraint on the relation between galaxy populations and dark matter halos.
- ID:
- ivo://CDS.VizieR/J/ApJ/625/6
- Title:
- Galaxy groups in the DEEP2 Galaxy Redshift Survey
- Short Name:
- J/ApJ/625/6
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We use the first 25% of the DEEP2 Galaxy Redshift Survey spectroscopic data to identify groups and clusters of galaxies in redshift space. The data set contains 8370 galaxies with confirmed redshifts in the range 0.7<=z<=1.4, over 1{deg}^2^ on the sky. Groups are identified using an algorithm (the Voronoi-Delaunay method) that has been shown to accurately reproduce the statistics of groups in simulated DEEP2-like samples. We optimize this algorithm for the DEEP2 survey by applying it to realistic mock galaxy catalogs and assessing the results using a stringent set of criteria for measuring group-finding success, which we develop and describe in detail here. We present the first DEEP2 group catalog, which assigns 32% of the galaxies to 899 distinct groups with two or more members, 153 of which have velocity dispersions above 350km/s. We provide locations, redshifts and properties for this high-dispersion subsample. This catalog represents the largest sample to date of spectroscopically detected groups at z~1.
- ID:
- ivo://CDS.VizieR/J/A+A/578/A61
- Title:
- Galaxy groups in the 2M++
- Short Name:
- J/A+A/578/A61
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We provide the galaxy group sample used as tracers of the large scale structure in the work to study the compact group environment.
- ID:
- ivo://CDS.VizieR/J/A+A/520/A42
- Title:
- Galaxy groups in the VIMOS-VLT Deep Survey
- Short Name:
- J/A+A/520/A42
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a homogeneous and complete catalogue of optical galaxy groups identified in the VIMOS-VLT Deep Survey (VVDS). We use mock catalogues extracted from the Millennium Simulation to study the potential systematics that might affect the overall distribution of the identified systems, and also to asses how well galaxy redshifts trace the line-of-sight velocity dispersion of the underlying mass overdensity. We train on these mock catalogues the adopted group-finding technique (the Voronoi-Delaunay Method, VDM), to recover in a robust and unbiased way the redshift and velocity dispersion distributions of groups and maximize the level of completeness (C) and purity (P) of the group catalogue. We identify 318(/144) VVDS groups with at least 2(/3) members within 0.2<=z<=1.0, globally with C=60% and P=50%. We use the group sample to study the redshift evolution of the fraction f_b_ of blue galaxies (U-B<=1) within 0.2<=z<=1 in both groups and in the whole ensemble of galaxies irrespectively of their environment.
- ID:
- ivo://CDS.VizieR/J/MNRAS/337/256
- Title:
- Galaxy in low X-ray luminosity clusters
- Short Name:
- J/MNRAS/337/256
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the first spectroscopic survey of intrinsically low X-ray luminosity clusters at z>>0, with Hubble Space Telescope (HST) WFPC2 imaging and spectroscopy from Calar Alto and WHT-LDSS2. We study 172 confirmed cluster members in a sample of ten clusters at 0.23<z<0.3, with LX<~4x10^43^h^-2^erg/s[0.1-2.4keV]. The core of each cluster is imaged with WFPC2 in the F702W filter, and the spectroscopic sample is statistically complete to Mr~-19.0+5logh, within an 11' (~1.8h^-1^Mpc) field. The clusters are dynamically well-separated from the surrounding field and most have velocity distributions consistent with Gaussians. The velocity dispersions range from 350-850km/s, consistent with the local L_X_-{sigma} correlation. All 10 clusters host a bright, giant elliptical galaxy without emission lines, near the centre of the X-ray emission. We measure the equivalent width of two nebular emission lines, [O II] and H{alpha}, and the H{delta} absorption line to classify the cluster members spectrally. Galaxy morphologies are measured from the HST images, using the two-dimensional surface-brightness fitting software GIM2D.
- ID:
- ivo://CDS.VizieR/J/ApJ/539/577
- Title:
- Galaxy morphologies in Cl 1358+62
- Short Name:
- J/ApJ/539/577
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We describe the morphological composition of a sample of 518 galaxies in the field of Cl 1358+62 at z=0.33, drawn from a large Hubble Space Telescope mosaic covering 53 square arcminutes. The sample is complete to I=22, corresponding to M_V_=-18.5 in the rest frame. The galaxy morphologies have been independently classified by the authors of this paper and by Alan Dressler. Dressler's classifications place our work in context with the previous MORPHS study and allow us to estimate the scatter between different sets of visual classifications. We restrict most of our analysis to the brighter part of the sample, I<21 (M_V_<-19.5), where the scatter between the two sets of classifications is 1 in morphological type.
- ID:
- ivo://CDS.VizieR/J/A+A/506/1071
- Title:
- Galaxy morphology in 5 medium redshift clusters
- Short Name:
- J/A+A/506/1071
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Following the study presented in our previous paper, based on the Nordic Optical Telescope (NOT) sample, which consists of five clusters of galaxies within the redshift range 0.18<=z<=0.25 imaged in the central 0.5-2Mpc in very good seeing conditions, we have studied the quantitative morphology of their bright galaxy population. We analyzed the surface brightness profiles of the galaxy population in those clusters, after performing simulations in order to check the reliability of the fits. We also derived a quantitative morphological classification.
- ID:
- ivo://CDS.VizieR/J/MNRAS/388/1537
- Title:
- Galaxy pairs from SDSS-DR2
- Short Name:
- J/MNRAS/388/1537
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We investigate the incidence of major mergers creating massive (M_star_>10^11^M_{sun}_) galaxies in present-day (z<=0.12) groups and clusters. Using a volume-limited sample of 845 groups with dark matter halo masses above 2.5x10^13^M_{sun}_, we isolate 221 galaxy pairs with <=1.5 r-band magnitude differences, <=30kpc projected separations and combined masses above 10^11^M_{sun}_. We fit the r-band images of each pair as the line-of-sight projection of symmetric models and identify 38 mergers by the presence of residual asymmetric structure associated with both progenitors, such as non-concentric isophotes, broad and diffuse tidal tails and dynamical friction wakes.
