2017/09/14 by C. P. Haines, A. Finoguenov, G. P. Smith +16 · 3 citations
Physics and Astronomy · #Accretion (finance) #Astronomy #Astrophysical Phenomena and Observations #Astrophysics #Cluster (spacecraft) #Galaxies: Formation, Evolution, Phenomena #Galaxy #Galaxy cluster #Galaxy group #Galaxy groups and clusters #Gamma-ray bursts and supernovae #Globular cluster #Halo #Mass segregation #Physics #Redshift #Star formation #Stellar mass #astro-ph.CO #astro-ph.GA
paper · pdf · doi:10.1093/mnras/sty651
20 pages, 17 figures. Submitted to MNRAS. Comments welcome
arxiv created 2017/09/14 · openalex created_date 2017/09/25 · openalex publication_date 2018/03/15 · arxiv updated 2018/04/04 · openalex updated_date 2026/08/05
Galaxy clusters are expected to form hierarchically in a cold dark matter ( CDM) universe, growing primarily through mergers with lower mass clusters and the continual accretion of group-mass haloes. Galaxy clusters assemble late, doubling their masses since z 0.5, and so the outer regions of clusters should be replete with accreting group-mass systems. We present an XMM-Newton survey to search for X-ray groups in the infall regions of 23 massive galaxy clusters ( M 200 10 15 M ) at z 0.2, identifying 39 X-ray groups that have been spectroscopically confirmed to lie at the cluster redshift. These groups have mass estimates in the range 2 10 13 -7 10 14 M , and group-to-cluster mass ratios as low as 0.02. The comoving number density of X-ray groups in the infall regions is 25 higher than that seen for isolated X-ray groups from the XXL survey. The average mass per cluster contained within these X-ray groups is 2.2 10 14 M , or 19 5 per cent of the mass within the primary cluster itself. We estimate that 10 15 M clusters increase their masses by 16 4 per cent between z = 0.223 and the present day due to the accretion of groups with M 200 10 13.2 M . This represents about half of the expected mass growth rate of clusters at these late epochs. The other half is likely to come from smooth accretion of matter not bound within haloes. The mass function of the infalling X-ray groups appears significantly top heavy with respect to that of 'field' X-ray systems, consistent with expectations from numerical simulations, and the basic consequences of collapsed massive dark matter haloes being biased tracers of the underlying large-scale density distribution.