Other
Scientific paper
Jan 1999
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1999aas...19312208g&link_type=abstract
American Astronomical Society, 193rd AAS Meeting, #122.08; Bulletin of the American Astronomical Society, Vol. 31, p.665
Other
Scientific paper
Galaxy clusters have been used to estimate H0 by combining observations of the decrement in the brightness temperature of the cosmic microwave background radiation (Sunyaev-Zel'dovich or SZ effect) with X-ray observations of the cluster gas. However, these H0 values appear to be lower than estimates computed by other methods (e.g., SNs). It has been proposed that this bias could be caused by mistakenly assuming that clusters contain isothermal gas in hydrostatic equilibrium when, in fact, they are undergoing violent cluster mergers. Abell 665 is an example of a cluster for which the Sunyaev-Zel'dovich analysis yields a low H0 value ( 40-50 km s-1 Mpc-1). Is this cluster undergoing a merger and, thus, biasing the H0 value obtained through the SZ effect? In this paper, we present an analysis of new optical data for a sample of 54 galaxies located at the cluster core. We find evidence of 1D and 3D substructure in the kinematical and spatial distributions of the galaxies that suggests that A665 is not dynamically relaxed. In fact, we believe that this cluster is undergoing a merger. We compare our observations with simple N-body numerical simulations of head on cluster mergers in order to better constrain some of the merger parameters such as the mass ratio, merger epoch, and viewing angle. Finally, we explore how this merger model affects the estimates of H0.
Birkinshaw Mark
Gomez Percy L.
Hughes John Patrick
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