Another X-ray-discovered poor cluster of galaxies associated with CL 0016 + 16

John P. Hughes*, Mark Birkinshaw

*Corresponding author for this work

Research output: Contribution to journalArticle (Academic Journal)peer-review

13 Citations (Scopus)


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 (σp = 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 × 1044 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 back-ground on inferred physical scales of 14-20 Mpc.

Original languageEnglish
Pages (from-to)645-649
Number of pages5
JournalAstrophysical Journal
Issue number2 PART I
Publication statusPublished - 1 Jan 1998


  • X-rays: galaxies


Dive into the research topics of 'Another X-ray-discovered poor cluster of galaxies associated with CL 0016 + 16'. Together they form a unique fingerprint.

Cite this