%R 1993ApJ...415...50C
%A Cavaliere, A.; Colafrancesco, S.; Menci, N.
%J Astrophysical Journal, Part 1, vol.415, no. 1, p. 50-57.
%D 09/1993
%P 50
%L 57
%T Distant clusters of galaxies detected by X-rays
%K Cosmic Plasma, Dark Matter, Galactic Clusters, X-ray Astronomy, Baryons, 
    Luminosity, Redshift
%B The dynamical masses of groups and clusters of galaxies decrease on average
 with increasing redshift, after the hierarchical cosmogonies dominated by
 direct collapses of dark matter overdensities. We show that the masses of
 intracluster plasma emitting in the X-ray band are to decrease more rapidly. We
 also show that consideration of the intrinsic spread in the dynamical formation
 times leads us to predict more numerous faint sources at given dynamical mass.
 The model we compute yields steeper luminosity functions in the X-ray band with
 a specific change in lookback time: the bright end shifts back. Such negative
 evolution is fast even at modest redshifts z less than about 0.5 if the
 external gas infalling into groups of clusters was preheated and has cooled
 down after z of about 1.5-2. If so, the evolution is considerably faster in the
 X-ray than in the optical band, comparing interestingly with data from the
 existing surveys.
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