2,969 research outputs found
Galactic extinction and Abell clusters
In this paper, we present the results of comparing the angular distribution
of Abell clusters with Galactic HI measurements. For most subsamples of
clusters considered, their positions on the sky appear to be anti-correlated
with respect to the distribution of HI column densities. The statistical
significance of these observed anti-correlations is a function of both richness
and distance class, with the more distant and/or richest systems having the
highest significance (~3 sigma). The lower richness, nearby clusters appear to
be randomly distributed compared to the observed Galactic HI column density.Comment: 5 pages, uuencoded compressed postscript file. Figures included.
Accepted by MNRA
A Bayesian Inference Analysis of the X-ray Cluster Luminosity-Temperature Relation
We present a Bayesian inference analysis of the Markevitch (1998) and Allen &
Fabian (1998) cooling flow corrected X-ray cluster temperature catalogs that
constrains the slope and the evolution of the empirical X-ray cluster
luminosity-temperature (L-T) relation. We find that for the luminosity range
10^44.5 erg s^-1 < L_bol < 10^46.5 erg s^-1 and the redshift range z < 0.5,
L_bol is proportional to T^2.80(+0.15/-0.15)(1+z)^(0.91-1.12q_0)(+0.54/-1.22).
We also determine the L-T relation that one should use when fitting the Press-
Schechter mass function to X-ray cluster luminosity catalogs such as the
Einstein Medium Sensitivity Survey (EMSS) and the Southern Serendipitous High-
Redshift Archival ROSAT Catalog (Southern SHARC), for which cooling flow
corrected luminosities are not determined and a universal X-ray cluster
temperature of T = 6 keV is assumed. In this case, L_bol is proportional to
T^2.65(+0.23/-0.20)(1+z)^(0.42-1.26q_0)(+0.75/-0.83) for the same luminosity
and redshift ranges.Comment: Accepted to The Astrophysical Journal, 20 pages, LaTe
A Search for X-Ray Bright Distant Clusters of Galaxies
We present the results of a search for X--ray luminous distant clusters of
galaxies. We found extended X--ray emission characteristic of a cluster towards
two of our candidate clusters of galaxies. They both have a luminosity in the
ROSAT bandpass of and a redshift of ;
thus making them two of the most distant X--ray clusters ever observed.
Furthermore, we show that both clusters are optically rich and have a known
radio source associated with them. We compare our result with other recent
searches for distant X--ray luminous clusters and present a lower limit of
for the number density of such high redshift
clusters. This limit is consistent with the expected abundance of such clusters
in a standard (b=2) Cold Dark Matter Universe. Finally, our clusters provide
important high redshift targets for further study into the origin and evolution
of massive clusters of galaxies. Accepted for publication in the 10th September
1994 issue of ApJ.Comment: 20 pages Latex file + 1 postscript figure file appende
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