Volume 367, Number 3, March I 2001
|Page(s)||801 - 808|
|Section||Cosmology (including clusters of galaxies)|
|Published online||15 March 2001|
The X-ray view of the quasar MR 2251-178 and its host cluster: Variability, absorption, and intracluster gas emission
Max-Planck-Institut für extraterrestrische Physik, Postfach 1312, 85741 Garching, Germany
Corresponding author: St. Komossa, firstname.lastname@example.org
Accepted: 13 December 2000
MR 2251-178 was the first quasar initially discovered in X-rays, and the first one found to host a warm absorber. The quasar turned out to be an outstanding object in many respects. It has a high ratio of X-ray/optical luminosity, is surrounded by the largest quasar emission-line nebula known, and is located in the outskirts of a cluster of galaxies. Here, we present results from an analysis of the X-ray spectral, temporal, and spatial properties of this source and its environment based on deep ROSAT observations. Remarkably, we do not detect any excess X-ray cold absorption expected to originate from the giant gas nebula surrounding MR 2251-178. This excludes the presence of a huge HI envelope around the quasar. The X-ray spectrum of MR 2251-178 is best fit by a warm-absorbed powerlaw with an ionization parameter and a column density which, however, cannot be the same material as the giant optical emission line nebula. The mean (0.1-2.4) keV X-ray luminosity amounts to 1045 erg/s. A spatial analysis shows that the bulk of the X-ray emission from the quasar is consistent with a point source, as expected in view of the powerlaw-shaped X-ray spectrum and the rapid X-ray variability we detect. In addition, extended emission appears at weak emission levels, including a bridge between the quasar and the cD galaxy of the cluster. The X-ray emission from the intra-cluster medium is weak or absent. We derive an upper limit on the X-ray luminosity of erg/s, weaker than other clusters of comparable richness. None of the other member galaxies of the cluster to which MR 2251-178 belongs, are detected in X-rays. However, east of the quasar there is a significant excess of X-ray sources, several of them without optical counterparts on the UK Schmidt plates.
Key words: galaxies: active / individual: MR 2251-178 / quasars / clusters / X-rays: galaxies
© ESO, 2001
Current usage metrics show cumulative count of Article Views (full-text article views including HTML views, PDF and ePub downloads, according to the available data) and Abstracts Views on Vision4Press platform.
Data correspond to usage on the plateform after 2015. The current usage metrics is available 48-96 hours after online publication and is updated daily on week days.
Initial download of the metrics may take a while.