arXiv subjects

Richard Mushotzky

Publications and source records attributed to Richard Mushotzky.

129 records · Page 8Linked to original sources

arXiv1997

Lack of Evolution in the Iron Abundance in Clusters of Galaxies and Implications for the Global Star Formation Rate at High Redshift

We present the first large sample of accurate iron abundances and temperatures for clusters at redshifts greater than 0.14. We find that the Fe abundance shows little or no evolution out to redshift 0.3. This and the early formation epoch of elliptical galaxies in clusters indicate that most of the enrichment of the intracluster medium occurred at redshifts greater than 1. If clusters represent fair samples of the universe, then global metal production is 2-5 times greater than is inferred from recent studies of galaxies at low and high redshifts.

astro-ph↗

arXiv1997

Systematic Errors in the Hubble Constant Based on Measurement of the Sunyaev-Zeldovich Effect

Values of the Hubble constant reported to date which are based on measurement of the Sunyaev-Zeldovich (SZ) effect in clusters of galaxies are systematically lower than those derived by other methods (e.g., Cepheid variable stars, or the Tully-Fisher relation). We investigate the possibility that systematic errors may be introduced into the analysis by the generally adopted assumptions that observed clusters are in hydrostatic equilibrium, are spherically symmetric, and are isothermal. We construct self-consistent theoretical models of merging clusters of galaxies using hydrodynamical/N-body simulations. We then compute the magnitude of Ho derived from the SZ effect at different times and at different projection angles both from first principles, and by applying each of the standard assumptions used in the interpretation of observations. Our results indicate that the assumption of isothermality in the evolving clusters can result in Ho being underestimated by 10-30% depending on both epoch and projection angle. Moreover, use of the projected, emission-weighted temperature profile under the assumption of spherical symmetry does not significantly improve the situation except in the case of more extreme mergers (i.e., those involving relatively gas-rich subclusters).

astro-ph↗

arXiv1996

The Mass of Abell 1060 and AWM 7 from Spatially Resolved X-ray Spectroscopy: Variations in Baryon Fraction

Using X-ray temperature and surface brightness profiles of the hot intracluster medium derived from ASCA and ROSAT observations we place constraints on the dark matter and baryon fraction distributions in the poor clusters Abell 1060 and AWM 7. Although their total mass distributions are similar, AWM 7 has twice the baryon fraction of Abell 1060 in the best-fit models. The functional form of the dark matter distribution is ill-determined, however mass models where the baryon fractions in Abell 1060 and AWM 7 significantly overlap are excluded. Such variations in baryon fraction are not predicted by standard models and imply that some mechanism in addition to gravity plays a major role in organizing matter on cluster scales.

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