AAS 201st Meeting, January, 2003
Session 67. Cosmic Gas: Long Ago and Far Away
Oral, Tuesday, January 7, 2003, 2:00-3:30pm, 606-607

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[67.06D] The Effects of Mergers on Thermal and Non-thermal Emission from Clusters of Galaxies as Studied Using Merger Trees

S. W. Randall, C. L. Sarazin (University of Virginia), P. M. Ricker (University of Illinois)

N-body/hydrodynamical simulations of merging galaxy clusters have shown that a merger can temporarily boost the X-ray luminosity and temperature of the merged cluster above the equilibrium values. The cumulative effect of these ``merger boosts'' will affect the observed X-ray luminosity functions (XLFs) and temperature functions (TFs) of clusters, which provide strong constraints on cosmological parameters. We use N-body/hydrodynamical simulations to derive boosts for individual mergers and Monte Carlo simulations of cluster merger histories (``merger trees'') to determine the cumulative effect of merger boosts. We find that merger boosts can have a significant effect on the XLFs and TFs inferred from X-ray observations. For example, in a Universe with \OmegaM = 0.3 and \Omega\Lambda = 0.7 at a redshift of z=1, the number of clusters with temperatures T >10 keV is increased by a factor of 9.5, and the number of clusters with luminosities LX > 5 \times 1044 h-2 erg s-1 is increased by a factor of 8.9. Merger boosts bias the values of \sigma8 and \OmegaM inferred from cluster XLFs and TFs if virial equilibrium is assumed. Merger boosts cause \sigma8 to be overestimated by about 20% and \OmegaM may be underestimated by about 20%.

We are currently using our merger tree code to evaluate the effect that cluster mergers have on non-thermal radio emission from clusters. Since cluster mergers also temporarily boost radio emission, it is possible that merger boosts may explain the observed steep relations between radio luminosity and X-ray luminosity or temperature. We have also shown that EUV emission from clusters of galaxies (due to inverse Compton scattering of the Cosmic Microwave Background) is a negligible component of the diffuse EUV background.

This work was supported in part by Chandra Award Numbers GO1-2123X and GO2-3159X and NASA XMM/Newton Grant NAG5-10075.

The author(s) of this abstract have provided an email address for comments about the abstract: swr3p@virginia.edu

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