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 ( \sim 10 ^ { 6 } 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 \sim 6 arcmin , inwards of this radius the EUV is absorbed by cold matter with a line-of-sight column density of \geq 2.7 \times 10 ^ { 19 } cm ^ { -2 } .
The centre of absorption is offset from that of the emission by \sim 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 \sim 5-10 times more massive than the hot .