From: Marc Postman (postman@stsci.edu)
Date: Fri Jan 13 2006 - 08:34:37 PST
Saul et al.,
Here is a plot that may demonstrate the point that early type galaxies
are strongly localized in the clusters for z > 1. This is a histogram
of spectroscopic redshifts for the clusters RXJ0910+54, RXJ1252-29, and
CL0848+44 (which are at z=1.10, 1.24, and 1.27, respectively). The red
histo is E+S0 galaxies and the blue histo is Sa or later. Relative to
the spikes seen in the field, the E+S0 overdensity in the cluster is
about a factor of 10 whereas the Sa+ overdensity is at best a factor of
2. There may be some selection effects in the spectroscopic selection
to slightly favor early types, however. But these effects, if corrected
for, might only increase the Sa+ peak at dz=0 by about 20 - 30% (but
would also probably increase the spikes in the field as well so that
the overall enhancement factor would probably still be only about a
factor of 2). The redshift range covered by this plot is 0.9 < z <
1.47.
Marc
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