2009/06/11 by Alastair J. R. Sanderson, Alastair C. Edge, Graham P. Smith · 3 citations
Physics and Astronomy · #Astronomy and Astrophysical Research #Brightest cluster galaxy #Cluster (spacecraft) #Galaxies: Formation, Evolution, Phenomena #Galaxy cluster #Intracluster medium #Offset (computer science) #Redshift #Stellar, planetary, and galactic studies #Substructure #astro-ph.CO #astro-ph.GA
paper · pdf · doi:10.1111/j.1365-2966.2009.15214.x
Added references; 8 pages, 7 figures; accepted for publication in MNRAS
arxiv created 2009/06/11 · openalex publication_date 2009/08/31 · arxiv updated 2015/05/13 · openalex created_date 2016/06/24 · openalex updated_date 2026/08/05
We study the distribution of projected offsets between the cluster X-ray centroid and the brightest cluster galaxy (BCG) for 65 X-ray-selected clusters from the Local Cluster Substructure Survey, with a median redshift of z= 0.23. We find a clear correlation between X-ray/BCG projected offset and the logarithmic slope of the cluster gas density profile at 0.04r500(α), implying that more dynamically disturbed clusters have weaker cool cores. Furthermore, there is a close correspondence between the activity of the BCG, in terms of detected Hα and radio emission, and the X-ray/BCG offset, with the line-emitting galaxies all residing in clusters with X-ray/BCG offsets of ≤15 kpc. Of the BCGs with α < −0.85 and an offset <0.02r500, 96 per cent (23/24) have optical emission and 88 per cent (21/24) are radio active, while none has optical emission outside these criteria. We also study the cluster gas fraction (fgas) within r500 and find a significant correlation with X-ray/BCG projected offset. The mean fgas of the ‘small offset’ clusters (<0.02r500) is 0.106 ± 0.005 (σ= 0.03) compared to 0.145 ± 0.009 (σ= 0.04) for those with an offset >0.02r500, indicating that the total mass may be systematically underestimated in clusters with larger X-ray/BCG offsets. Our results imply a link between cool core strength and cluster dynamical state consistent with the view that cluster mergers can significantly perturb cool cores, and set new constraints on models of the evolution of the intracluster medium.