EUV and X-ray observations of Abell 2199: a three-phase intracluster medium with a massive warm component
Abstract
Various independent ways of constraining key cosmological parameters yielded a consensus range of values which indicates that at the present epoch the bulk of the universe's baryons is in the form of a warm ( ~ 106 K) gas - a temperature regime which renders them difficult to detect. The discovery of EUV and soft X-ray excess emission from clusters of galaxies was originally interpreted as the first direct evidence for the large scale presence of such a warm component. We present results from an EUVE Deep Survey (DS) observation of the rich cluster Abell 2199 in the Lex/B (69-190 eV) filter passband. The soft excess radial trend (SERT), shown by a plot against cluster radius r of the percentage EUV emission eta observed above the level expected from the hot intracluster medium (ICM), behaves as a simple function of r which decreases monotonically towards r = 0; it smoothly turns negative at r ~ 6 arcmin, inwards of this radius the EUV is absorbed by cold matter with a line-of-sight column density of >= 2.7 x 1019 cm-2. The centre of absorption is offset from that of the emission by ~ 1 arcmin, and the area involved is much larger than that of the cooling flow. These facts together provide strong evidence for a centrally concentrated but cluster-wide distribution of clumps of cold gas which co-exist with warm gas of similar spatial properties. Further, the simultaneous modeling of EUV and X-ray data requires a warm component even within the region of absorption. The phenomenon demonstrates a three phase ICM, with the warm phase estimated to be ~ 5-10 times more massive than the hot.
- Publication:
-
Astronomy and Astrophysics
- Pub Date:
- December 2000
- DOI:
- 10.48550/arXiv.astro-ph/0010610
- arXiv:
- arXiv:astro-ph/0010610
- Bibcode:
- 2000A&A...364..497L
- Keywords:
-
- GALAXIES: INTERGALACTIC MEDIUM;
- GALAXIES: COOLING FLOWS;
- Astrophysics
- E-Print:
- 9 pages, 4 figures (1 in color), A&