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

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 \Omega_M = 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 L_X > 5 \times 10⁴⁴ h^-2 erg s^-1 is increased by a factor of 8.9. Merger boosts bias the values of \sigma₈ and \Omega_M inferred from cluster XLFs and TFs if virial equilibrium is assumed. Merger boosts cause \sigma₈ to be overestimated by about 20% and \Omega_M 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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