We present relations between X-ray luminosity and velocity dispersion (L − σ), X-ray luminosity and gas mass (L − M gas ), and cluster radius and velocity dispersion (r 500 − σ) for 62 galaxy clusters in the HIFLUGCS, an X-ray flux-limited sample minimizing bias toward any cluster morphology. Our analysis in total is based on ∼1.3 Ms of clean X-ray XMM-Newton data and 13439 cluster member galaxies with redshifts. Cool cores are among the major contributors to the scatter in the L − σ relation. When the cool-core-corrected X-ray luminosity is used the intrinsic scatter decreases to 0.27 dex. Even after the X-ray luminosity is corrected for the cool core, the scatter caused by the presence of cool cores dominates for the low-mass systems. The scatter caused by the non-cool-core clusters does not strongly depend on the mass range, and becomes dominant in the high-mass regime. The observed L − σ relation agrees with the self-similar prediction, matches that of a simulated sample with AGN feedback disregarding six clusters with <45 cluster members with spectroscopic redshifts, and shows a common trend of increasing scatter toward the low-mass end, i.e., systems with σ ≤ 500 km s −1 . A comparison of observations with simulations indicates an AGN-feedback-driven impact in the low-mass regime. The best fits to the L − M gas relations for the disturbed clusters and undisturbed clusters in the observational sample closely match those of the simulated samples with and without AGN feedback, respectively. This suggests that one main cause of the scatter is AGN activity providing feedback in different phases, e.g. during a feedback cycle. The slope and scatter in the observed r 500 − σ relation is similar to that of the simulated sample with AGN feedback except for a small offset but still within the scatter.

No abstract

We present Very Large Array H i imaging data for a field in the NW of the galaxy cluster Abell 1367 (z= 0.02) in an attempt to probe the effect environment has on the interstellar medium of late‐type spiral galaxies. Several galaxies, like CGCG 097–087, show pronounced tails and asymmetries, and seven out of 10 show significant, several kpc offsets between the H i centroid and the optical. We compare our results against a sample of optically bright, late‐type galaxies (spirals) across the central 1.5 Mpc of the cluster taken from the Arecibo Galaxy Environment Survey. We find that these late‐type spirals are predominantly found in the northern half of the cluster, especially those that are relatively gas rich. We calculate the H i deficiency and find that the expected global trend for the H i deficiency of these spirals to increase with projected proximity to the cluster core, seen in clusters like Coma and Virgo, is not observed. We classified the spirals into four evolutionary states, with the galaxies in each state sharing a similar degree of H i deficiency and optical colour. The common characteristics of the spirals in each evolutionary state suggest they have been subject to similar environmental processes. Many of the spirals in the most common evolutionary state (moderate H i deficiency and blue colour) have an H i intensity maximum which is displaced relative to its optical counterpart. The orientation of these offsets and magnitude of their H i deficiencies together with data from other wavelengths provide observational evidence in support of varying degrees of ram pressure stripping and tidal interaction. In general, our results indicate that the H i discs of bright late‐type galaxies in the central part of the cluster are subject to both gas loss and morphological disturbance as a result of their interaction with the cluster environment. This provides further observational evidence of a more complex environment in Abell 1367 as compared to Virgo and Coma.

Context. In the currently debated context of using clusters of galaxies as cosmological probes, the need for well-defined cluster samples is critical. Aims. The XXL Survey has been specifically designed to provide a well characterised sample of some 500 X-ray detected clusters suitable for cosmological studies. The main goal of present article is to make public and describe the properties of the cluster catalogue in its present state, as well as of associated catalogues of more specific objects such as super-clusters and fossil groups. Methods. Following from the publication of the hundred brightest XXL clusters, we now release a sample containing 365 clusters in total, down to a flux of a few 10−15 erg s−1 cm−2 in the [0.5–2] keV band and in a 1′ aperture. This release contains the complete subset of clusters for which the selection function is well determined plus all X-ray clusters which are, to date, spectroscopically confirmed. In this paper, we give the details of the follow-up observations and explain the procedure adopted to validate the cluster spectroscopic redshifts. Considering the whole XXL cluster sample, we have provided two types of selection, both complete in a particular sense: one based on flux-morphology criteria, and an alternative based on the [0.5–2] keV flux within 1 arcmin of the cluster centre. We have also provided X-ray temperature measurements for 80% of the clusters having a flux larger than 9 × 10−15 erg s−1 cm−2. Results. Our cluster sample extends from z ~ 0 to z ~ 1.2, with one cluster at z ~ 2. Clusters were identified through a mean number of six spectroscopically confirmed cluster members. The largest number of confirmed spectroscopic members in a cluster is 41. Our updated luminosity function and luminosity–temperature relation are compatible with our previous determinations based on the 100 brightest clusters, but show smaller uncertainties. We also present an enlarged list of super-clusters and a sample of 18 possible fossil groups. Conclusions. This intermediate publication is the last before the final release of the complete XXL cluster catalogue when the ongoing C2 cluster spectroscopic follow-up is complete. It provides a unique inventory of medium-mass clusters over a 50 deg2 area out to z ~ 1.

In this series of papers we explore the evolution of late-type galaxies in the rich cluster Abell 85. In this first paper we revisit the complex dynamical state of A 85 by using independent methods. First, we analyze the galaxy redshift distribution towards A 85 in the whole range 0−40 000 km s −1 , and determine the mean redshifts of the background clusters A 87 and A 89, very close in projection to A 85. Then we search for substructures in A 85 by considering the 2D galaxy distribution of its members (13 000−20 000 km s −1 ) and by applying the kinematical 3D Δ-test to both projected positions and radial velocities. This clearly reveals several substructures: one close to the cluster core and three more projected towards the southeast, along the region where an X-ray filament has been extensively studied. We also analyse the distribution of the brightest blue galaxies across a major fraction of the cluster volume, considering if they are gas-rich or poor. We report a very asymmetric distribution of the blue member galaxies, with most of them to the east and southeast, namely in the region joining the core of A 85 to its farthest substructure in this direction -dubbed the SE clump. By matching our sample of bright blue member galaxies with H i detections reported in the literature, we identify gas-rich and gas-poor ones. As expected, the H i-rich blue galaxies follow the same trend as the parent sample, with most of them projected on the eastern side of the cluster as well. Interestingly no blue objects have been detected in H i up to a projected radius of 2 Mpc in this zone. We finally estimate the ram pressure stripping exerted by the intra-cluster medium as a function of the projected distance from A 85, in order to quantify how important this mechanism might be in sweeping the gas out of the infalling spirals.

We present two new catalogues of superclusters of galaxies out to a redshift of z = 0.15, based on the Abell/ACO cluster redshift compilation maintained by one of us (HA). The first of these catalogues, the all-sky Main SuperCluster Catalogue (MSCC), is based on only the rich (A-) Abell clusters, and the second one, the Southern SuperCluster Catalogue (SSCC), covers declinations δ < −17• and includes the supplementary Abell S-clusters. A tunable Friends-of-Friends (FoF) algorithm was used to account for the cluster density decreasing with redshift and for different selection functions in distinct areas of the sky. We present the full list of Abell clusters used, together with their redshifts and supercluster memberships and including the isolated clusters. The SSCC contains about twice the number of superclusters than MSCC for δ < −17• , which we found to be due to: (1) new superclusters formed by A-clusters in their cores and surrounded by S-clusters (50%), (2) new superclusters formed by S-clusters only (40%), (3) redistribution of member clusters by fragmentation of rich (multiplicity m > 15) superclusters (8%), and (4) new superclusters formed by the connection of A-clusters through bridges of S-clusters (2%). Power-law fits to the cumulative supercluster multiplicity function yield slopes of α = −2.0 and α = −1.9 for MSCC and SSCC respectively. This power-law behavior is in agreement with the findings for other observational samples of superclusters, but not with that of catalogues based on cosmological simulations.

A large sample of Abell clusters of galaxies, selected for the likely presence of a dominant galaxy, is used to study the dynamical properties of the brightest cluster members (BCMs). From visual inspection of Digitized Sky Survey images

Abstract. We present the X-ray luminosity versus dynamical mass relation for 63 nearby clusters of galaxies in a flux-limited sample, the HIFLUGCS (consisting of 64 clusters). The luminosity measurements are obtained based on ∼ 1.3 Ms of clean XMM-Newton data and ROSAT pointed observations. The masses are estimated using optical spectroscopic redshifts of 13647 cluster galaxies in total. We classify clusters into disturbed and undisturbed ones, based on a combination of the X-ray luminosity concentration and the offset between the brightest cluster galaxy and X-ray flux-weighted center. Given sufficient numbers (i.e. ≥45) of member galaxies in computing the dynamical masses, the luminosity versus mass relations agree between the disturbed and undisturbed clusters. The cool-core clusters still dominate the scatter in the luminosity versus mass relation even when a core corrected X-ray luminosity is used, which indicates that the scatter of this scaling relation mainly reflects the structure formation history of the clusters. As shown by the clusters with a small number of spectroscopically confirmed members, the dynamical masses can be underestimated and thus lead to a biased scaling relation. To investigate the potential of spectroscopic surveys to follow up high-redshift galaxy clusters/groups observed in X-ray surveys for the identifications and mass calibrations, we carried out Monte-Carlo re-sampling of the cluster galaxy redshifts and calibrated the uncertainties of the redshift and dynamical mass estimates when only reduced numbers of galaxy redshifts per cluster are available. The re-sampling considers the SPIDERS and 4MOST configurations, designed for the follow-up of the eROSITA clusters, and was carried out for each cluster in the sample at the actual cluster redshift as well as at the assigned input cluster redshifts of 0.2, 0.4, 0.6, and 0.8. For following up very distant cluster/groups, we also carried out the mass calibration based on the re-sampling with only ten redshifts per cluster, and redshift calibration based on the re-sampling with only five and ten redshifts per cluster, respectively. Our results demonstrate the power of combining upcoming X-ray and optical spectroscopic surveys for mass calibration of clusters. The scatter in the dynamical mass estimates for the clusters with at least ten members is within 50%.