2000/10/30 by Richard Lieu, Lieu, Richard, Max Bonamente +3
Physics and Astronomy · #Astrophysics (astro-ph) #FOS: Physical sciences #astro-ph
paper · pdf · doi:10.48550/arxiv.astro-ph/0010610
9 pages, 4 figures (1 in color), A&A in press
arxiv created 2000/10/30 · arxiv updated 2009/12/01
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 η 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 × 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.