1997/11/18 by John P. Hughes, Mark Birkinshaw · 17 citations
Physics and Astronomy · #Astronomy and Astrophysical Research #Astrophysical Phenomena and Observations #Cluster (spacecraft) #Galaxies: Formation, Evolution, Phenomena #Galaxy #Galaxy cluster #Galaxy groups and clusters #Luminosity #Luminosity function #ROSAT #Velocity dispersion #astro-ph
paper · pdf · doi:10.1086/305512
published in The Astrophysical Journal 497(2), 645-649 (IOP Publishing) · 16 pages, including 3 postscript figs, LaTeX. To appear in ApJ
arxiv created 1997/11/18 · openalex publication_date 1998/04/20 · arxiv updated 2009/12/01 · openalex created_date 2016/06/24 · openalex updated_date 2026/08/05
We report optical spectroscopic observations of RX J0018.8+1602, a ROSAT X-ray source proposed to be an intermediate-redshift cluster of galaxies. Our observations confirm the identification of RX J0018.8+1602 and provide measurements of its mean radial velocity ( z = 0.5406 ± 0.0006) and velocity dispersion (σ p =200 −80 +110 km s -1 ). This is the second poor cluster that has been found to be a companion to CL 0016+16 ( z = 0.5455), the other one being RX J0018.3+1618 ( z = 0.5506). The 0.2-2 keV band source-frame X-ray luminosity summed over both companion clusters is 5 × 10 44 ergs s -1 , which is a significant fraction (~23%) of the X-ray luminosity of the main cluster. The companions are located at angular distances of 10'-25' (minimum physical scales of 5-12 Mpc) from CL 0016+16, and we propose that they represent a new large-scale component of the X-ray emission from clusters of galaxies. Similar low X-ray luminosity poor clusters surrounding nearby Abell clusters can explain the excess power observed in the angular cross-correlation function between Abell clusters and the X-ray background on inferred physical scales of 14-20 Mpc.