- ID:
- ivo://CDS.VizieR/J/ApJ/805/3
- Title:
- Profiles of clusters of galxies from Chandra
- Short Name:
- J/ApJ/805/3
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- A sample of 46 nearby clusters observed with Chandra is analyzed to produce radial density, temperature, entropy, and metallicity profiles, as well as other morphological measurements. The entropy profiles are computed to larger radii than in previous Chandra cluster sample analyses. We find that the iron mass fraction measured in the inner 0.15R_500_ shows a larger dispersion across the sample of low-mass clusters than it does for the sample of high-mass clusters. We interpret this finding as the result of the mixing of more halos in large clusters than in small clusters, leading to an averaging of the metallicity in the large clusters, and thus less dispersion of metallicity. This interpretation lends support to the idea that the low-entropy, metal-rich gas of merging halos reaches the clusters' centers, which explains observations of core-collapse supernova product metallicity peaks, and which is seen in hydrodynamical simulations. The gas in these merging halos would have to reach cluster centers without mixing in the outer regions. On the other hand, the metallicity dispersion does not change with mass in the outer regions of the clusters, suggesting that most of the outer metals originate from a source with a more uniform metallicity level, such as during pre-enrichment. We also measure a correlation between the metal content in low-mass clusters and the morphological disturbance of their intracluster medium, as measured by centroid shift. This suggests an alternative interpretation, whereby transitional metallicity boosts in the center of low-mass clusters account for the larger dispersion of their metallicities.
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- ID:
- ivo://CDS.VizieR/J/ApJS/174/117
- Title:
- Properties and metal abundances of clusters
- Short Name:
- J/ApJS/174/117
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have assembled a sample of 115 galaxy clusters at 0.1<z<1.3 with archived Chandra ACIS-I observations. We present X-ray images of the clusters and make available region files containing contours of the smoothed X-ray emission. The structural properties of the clusters were investigated, and we found a significant absence of relaxed clusters (as determined by centroid shift measurements) at z>0.5. The slope of the surface brightness profiles at large radii were steeper on average by 15% than the slope obtained by fitting a simple {beta}-model to the emission. This slope was also found to be correlated with cluster temperature, with some indication that the correlation is weaker for the clusters at z>0.5. We measured the mean metal abundance of the cluster gas as a function of redshift and found significant evolution, with the abundances dropping by 50% between z=0.1 and z~1. This evolution was still present (although less significant) when the cluster cores were excluded from the abundance measurements, indicating that the evolution is not solely due to the disappearance of relaxed, cool core clusters (which are known to have enhanced core metal abundances) from the population at z>~0.5.
- ID:
- ivo://CDS.VizieR/J/MNRAS/497/2163
- Title:
- Properties of galaxy group sample
- Short Name:
- J/MNRAS/497/2163
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Our understanding of how active galactic nucleus feedback operates in galaxy clusters has improved in recent years owing to large efforts in multiwavelength observations and hydrodynamical simulations. However, it is much less clear how feedback operates in galaxy groups, which have shallower gravitational potentials. In this work, using very deep Very Large Array and new MeerKAT observations from the MIGHTEE survey, we compiled a sample of 247 X-ray selected galaxy groups detected in the COSMOS field. We have studied the relation between the X-ray emission of the intra-group medium and the 1.4GHz radio emission of the central radio galaxy. For comparison, we have also built a control sample of 142 galaxy clusters using ROSAT and NVSS data. We find that clusters and groups follow the same correlation between X-ray and radio emission. Large radio galaxies hosted in the centres of groups and merging clusters increase the scatter of the distribution. Using statistical tests and Monte Carlo simulations, we show that the correlation is not dominated by biases or selection effects. We also find that galaxy groups are more likely than clusters to host large radio galaxies, perhaps owing to the lower ambient gas density or a more efficient accretion mode. In these groups, radiative cooling of the intra-cluster medium could be less suppressed by active galactic nucleus heating. We conclude that the feedback processes that operate in galaxy clusters are also effective in groups.
- ID:
- ivo://CDS.VizieR/J/ApJ/817/85
- Title:
- Properties of giant arcs behind CLASH clusters
- Short Name:
- J/ApJ/817/85
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We developed an algorithm to find and characterize gravitationally lensed galaxies (arcs) to perform a comparison of the observed and simulated arc abundance. Observations are from the Cluster Lensing And Supernova survey with Hubble (CLASH). Simulated CLASH images are created using the MOKA package and also clusters selected from the high-resolution, hydrodynamical simulations, MUSIC, over the same mass and redshift range as the CLASH sample. The algorithm's arc elongation accuracy, completeness, and false positive rate are determined and used to compute an estimate of the true arc abundance. We derive a lensing efficiency of 4+/-1 arcs (with length >=6" and length-to-width ratio >=7) per cluster for the X-ray-selected CLASH sample, 4+/-1 arcs per cluster for the MOKA-simulated sample, and 3+/-1 arcs per cluster for the MUSIC-simulated sample. The observed and simulated arc statistics are in full agreement. We measure the photometric redshifts of all detected arcs and find a median redshift z_s_=1.9 with 33% of the detected arcs having z_s_>3. We find that the arc abundance does not depend strongly on the source redshift distribution but is sensitive to the mass distribution of the dark matter halos (e.g., the c-M relation). Our results show that consistency between the observed and simulated distributions of lensed arc sizes and axial ratios can be achieved by using cluster-lensing simulations that are carefully matched to the selection criteria used in the observations.
- ID:
- ivo://CDS.VizieR/J/A+AS/146/373
- Title:
- Properties of nearby clusters of galaxies. IV.
- Short Name:
- J/A+AS/146/373
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- This paper is the fourth of a series (Trevese et al. 1992, Paper I, Cat. <J/A+AS/94/327>, Flin et al. 1995, Cat. <J/A+AS/110/313>, Paper II, Trevese et al. 1997, Cat. <J/A+AS/125/459>, Paper III) presenting F band photometry, from digitized 48-inch Palomar plates, of the galaxies brighter than m_3+3 10 clusters of galaxies. For each galaxy, equatorial coordinates, magnitude, size, ellipticity and orientation are given. We provide finding charts and contour maps of the galaxy surface density for each cluster.
- ID:
- ivo://CDS.VizieR/J/ApJ/496/39
- Title:
- Properties of poor groups of galaxies. I.
- Short Name:
- J/ApJ/496/39
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We use multifiber spectroscopy of 12 poor groups of galaxies to address (1) whether the groups are bound systems or chance projections of galaxies along the line of sight; (2) why the members of each group have not already merged to form a single galaxy, despite the groups' high galaxy densities, short crossing times, and likely environments for galaxy-galaxy mergers; and (3) how galaxies might evolve in these groups, where the collisional effects of the intragroup gas and the tidal influences of the global potential are weaker than in rich clusters. Each of the 12 groups has fewer than about five cataloged members in the literature. Our sample consists of 1002 galaxy velocities, 280 of which are group members. The groups have mean recessional velocities between 1600 and 7600km/s. Nine groups, including three Hickson compact groups, have the extended X-ray emission characteristic of an intragroup medium (see Paper II, 1998ApJ...496...73M).
- ID:
- ivo://CDS.VizieR/J/ApJ/539/136
- Title:
- Properties of poor groups of galaxies. III.
- Short Name:
- J/ApJ/539/136
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The form of the galaxy luminosity function (GLF) in poor groups - regions of intermediate galaxy density that are common environments for galaxies - is not well understood. Multiobject spectroscopy and wide-field CCD imaging now allow us to measure the GLF of bound group members directly (i.e., without statistical background subtraction) and to compare the group GLF with the GLFs of the field and of rich clusters. We use R-band images in 1.5x1.5degree^2^ mosaics to obtain photometry for galaxies in the fields of six nearby (2800<cz<7700km/s) poor groups for which we have extensive spectroscopic data, including 328 new galaxy velocities.
- ID:
- ivo://CDS.VizieR/J/A+A/607/A81
- Title:
- Properties of the sample of clusters
- Short Name:
- J/A+A/607/A81
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The relation between a cosmological halo concentration and its mass (cMr) is a powerful tool to constrain cosmological models of halo formation and evolution. On the scale of galaxy clusters the cMr has so far been determined mostly with X-ray and gravitational lensing data. The use of independent techniques is helpful in assessing possible systematics. Here we provide one of the few determinations of the cMr by the dynamical analysis of the projected-phase-space distribution of cluster members. Based on the WINGS and OmegaWINGS data sets, we used the Jeans analysis with the MAMPOSSt technique to determine masses and concentrations for 49 nearby clusters, each of which has >~60 spectroscopic members within the virial region, after removal of substructures. Our cMr is in statistical agreement with theoretical predictions based on {LAMBDA}CDM cosmological simulations. Our cMr is different from most previous observational determinations because of its flatter slope and lower normalization. It is however in agreement with two recent cMr obtained using the lensing technique on the CLASH and LoCuSS cluster data sets. The dynamical study of the projected-phase-space of cluster members is an independent and valid technique to determine the cMr of galaxy clusters. Our cMr shows no tension with theoretical predictions from {LAMBDA}CDM cosmological simulations for low-redshift, massive galaxy clusters. In the future we will extend our analysis to galaxy systems of lower mass and at higher redshifts.
- ID:
- ivo://CDS.VizieR/J/ApJ/812/34
- Title:
- Properties of UCD candidates in M87/M49/M60 regions
- Short Name:
- J/ApJ/812/34
- Date:
- 14 Jan 2022 08:28:26
- Publisher:
- CDS
- Description:
- We use imaging from the Next Generation Virgo cluster Survey (NGVS) to present a comparative study of ultra-compact dwarf (UCD) galaxies associated with three prominent Virgo sub-clusters: those centered on the massive red-sequence galaxies M87, M49, and M60. We show how UCDs can be selected with high completeness using a combination of half-light radius and location in color-color diagrams (u*iK_s_ or u*gz). Although the central galaxies in each of these sub-clusters have nearly identical luminosities and stellar masses, we find large differences in the sizes of their UCD populations, with M87 containing ~3.5 and 7.8 times more UCDs than M49 and M60, respectively. The relative abundance of UCDs in the three regions scales in proportion to sub-cluster mass, as traced by X-ray gas mass, total gravitating mass, number of globular clusters (GCs), and number of nearby galaxies. We find that the UCDs are predominantly blue in color, with ~85% of the UCDs having colors similar to blue GCs and stellar nuclei of dwarf galaxies. We present evidence that UCDs surrounding M87 and M49 may follow a morphological sequence ordered by the prominence of their outer, low surface brightness envelope, ultimately merging with the sequence of nucleated low-mass galaxies, and that envelope prominence correlates with distance from either galaxy. Our analysis provides evidence that tidal stripping of nucleated galaxies is an important process in the formation of UCDs.
- ID:
- ivo://CDS.VizieR/J/A+A/620/A186
- Title:
- Properties of VIS3COS galaxies
- Short Name:
- J/A+A/620/A186
- Date:
- 02 Mar 2022 11:37:55
- Publisher:
- CDS
- Description:
- We present the VIMOS Spectroscopic Survey of a Supercluster in the COSMOS field (VIS^3^COS) at z~0.84. We use VIMOS high-resolution spectra (GG475 filter) to spectroscopically select 490 galaxies in and around the superstructure and an additional 481 galaxies in the line of sight. We present the redshift distribution, the catalogue to be made public, and the first results on the properties of individual galaxies and stacked spectra (3500{AA}<{lambda}<4200{AA} rest-frame). We probe a wide range of densities and environments (from low-density field to clusters and rich groups). We find a decrease in the median star formation rate from low- to high-density environments in all bins of stellar mass and a sharp rise of the quenched fraction {(from ~10% to ~40-60%)} of intermediate-stellar-mass galaxies (10<log_10_M*/M_{sun}_)<10.75) from filaments to clusters. The quenched fraction for massive galaxies shows little dependence on environment, being constant at ~30-40%. We find a break in the strength of the [OII] emission, with nearly constant line equivalent widths at lower densities (~-11{AA}) and then a drop to ~-2.5{AA} towards higher densities. The break in the [OII] line strength happens at similar densities (log_10_(1+{delta})~0.0-0.5) as the observed rise in the quenched fraction. Our results may provide further clues regarding the different environmental processes affecting galaxies with different stellar masses and highlight the advantages of a single dataset in the COSMOS field probing a wide range of stellar masses and environments. We hypothesise that quenching mechanisms are enhanced in high-density regions.
