The ROSAT Brightest Cluster Sample -- I. The compilation of the sample and the cluster log N--log S distribution

Abstract

We present a 90 per cent flux‐complete sample of the 201 X‐ray‐brightest clusters of galaxies in the northern hemisphere (δ ≥ 0°), at high Galactic latitudes (|b| ≥ 20°), with measured redshifts z ≤ 0.3 and fluxes higher than 4.4 × 10−12 erg cm−2 s−1 in the 0.1–2.4 keV band. The sample, called the ROSAT Brightest Cluster Sample (BCS), is selected from ROSAT All‐Sky Survey data and is the largest X‐ray‐selected cluster sample compiled to date. In addition to Abell clusters, which form the bulk of the sample, the BCS also contains the X‐ray‐brightest Zwicky clusters and other clusters selected from their X‐ray properties alone. Effort has been made to ensure the highest possible completeness of the sample and the smallest possible contamination by non‐cluster X‐ray sources. X‐ray fluxes are computed using an algorithm tailored for the detection and characterization of X‐ray emission from galaxy clusters. These fluxes are accurate to better than 15 per cent (mean 1σ error). We find the cumulative log N–log S distribution of clusters to follow a power law κSα with α = 1.31+0.06−0.03 (errors are the 10th and 90th percentiles) down to fluxes of 2 × 10−12 erg cm−2 s−1, i.e. considerably below the BCS flux limit. Although our best‐fitting slope disagrees formally with the canonical value of −1.5 for a Euclidean distribution, the BCS log N–log S distribution is consistent with a non‐evolving cluster population if cosmological effects are taken into account. Our sample will allow us to examine large‐scale structure in the northern hemisphere, determine the spatial cluster–cluster correlation function, investigate correlations between the X‐ray and optical properties of the clusters, establish the X‐ray luminosity function for galaxy clusters, and discuss the implications of the results for cluster evolution.

LoCuSS: weak-lensing mass calibration of galaxy clusters

“…The sample comprises 50 clusters (Table 1) drawn from the ROSAT All Sky Survey cluster catalogues (Ebeling et al 1998(Ebeling et al , 2000Böhringer et al 2004) that satisfy the criteria: −25 • < δ < +65 • , nH 7 × 10 20 cm −2 , 0.15 z 0.3, LX /E(z) > 4.1 × 10 44 erg s −1 where LX is in the 0.1 − 2.4 keV band and E(z) = ΩM (1 + z) 3 + ΩΛ. The sample is X-ray luminosity-limited, and therefore approximately mass-limited.…”

JVLA S- and X-band polarimetry of the merging cluster Abell 2256

“…′′ 2) in the J2000 epoch (Ebeling et al 1998). Berrington et al (2002) investigated Abell 2256 with optical observations and found substructures of member galaxies with the peak radial velocity difference of ∼ 2000 km s −1 .…”

“…We can analytically model the fractional polarization in the cases of the EFD and IFD using the Burn's law (Burn 1966). The fractional Ebeling et al (1998).…”

The bow shock, cold fronts and disintegrating cool core in the merging galaxy group RX J0751.3+5012

“…The spectra were fitted in XSPEC 12.8 (Arnaud 1996) with an absorbed single temperature APEC model version 2.0.2 (Smith et al 2001). The cluster redshift was fixed to z = 0.022 (Ebeling et al 1998;Crawford et al 1999) and abundances were measured assuming the abundance ratios of Anders & Grevesse (1989). The temperature, metallicity and normalization parameters were left free.…”