Properties of the double β model for intracluster gas |
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Authors: | Yan-Jie Xue Xiang-Ping Wu |
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Institution: | Beijing Astronomical Observatory and National Astronomical Observatories, Chinese Academy of Sciences, Beijing 100012, China |
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Abstract: | We present an extensive study of the double β model for the X-ray surface brightness profiles of clusters, and derive analytically the gas density and total masses of clusters under the hydrostatic equilibrium hypothesis. It is shown that the employment of the double β model instead of the conventional single β model can significantly improve the goodness-of-fit to the observed X-ray surface brightness profiles of clusters, which will in turn lead to a better determination of the gas and total mass distributions in clusters. In particular, the observationally fitted β parameter for the extended component in a double β model may become larger. This opens a new possibility of resolving the long-standing β discrepancy for clusters. Using an ensemble of 33 ROSAT PSPC observed clusters drawn from the Mohr, Mathiesen & Evrard sample, we find that the asymptotic value of β fit is 0.83±0.33 at large radii, consistent with both the average spectroscopic parameter β spec=0.78±0.37 and the result given by numerical simulations. |
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Keywords: | galaxies: clusters: general intergalactic medium X-rays: galaxies |
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