Session 53 - Surveys of Galaxies & Clusters.
Display session, Tuesday, January 16
North Banquet Hall, Convention Center
[53.03] A Statistically Complete Sample of Poor Galaxy Clusters
M. J. Ledlow, C. Loken, J. O. Burns (NMSU), R. A. White (GSFC)
We have constructed a statistically complete, volume-limited, optically
selected sample of poor galaxy clusters from the catalog of White et al. (1996).
The sample is selected from an electronic version of the Zwicky et al. (1961-1968)
catalog, and includes groups with surface-density enhancements 46 times the
field density in the north galactic cap, at least 4
Zwicky galaxies, and with |b|\geq 30^\circ.
The resulting sample has 67 poor clusters, 50 of which
fall within our volume-limited sample for 0.01Only about half of the sample has more than 2 published redshifts. We have
obtained optical spectra using the Apache Point Observatory 3.5-m telescope
for several galaxies in each group in order to define the sample. 63% of
the groups now have more than 5 velocities. We examine the distribution of
velocity dispersions and other optical properties of this sample. A majority
of these clusters have VLA radio observations, and we have X-ray imaging from
the ROSAT All-Sky-Survey for the entire sample. Approximately 50% of the
groups have X-ray detections. Nearly all of the clusters show evidence of
extended intracluster gas in addition to individual galaxy emission from the
hot ISM. We are using these combined data, together with rich cluster
samples, to study the continuity in properties between rich and poor clusters,
the relationship between radio emission and the intracluster medium, and the
relationship between the optical properties of the cluster galaxies and
radio/X-ray detections. Additionally, we are using the observed
X-ray luminosity function and derived mass function for our poor clusters in order
to test and constrain cosmological models from the 512x512 CHDM simulation of
Bryan et al. (1996).
This work is supported by a NASA long-term space astrophysics grant NAGW-3152
and NSF grant AST-9317596.
listing for Tuesday