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Article overview
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Updating the $sigma$-$T$ relationship for galaxy clusters | | Xiang-Ping Wu
; Li-Zhi Fang
; Wen Xu
; | | Date: |
18 Aug 1998 | | Subject: | astro-ph | | Abstract: | The relationship between the X-ray determined temperature $T$ of the intracluster gas and the optical measured velocity dispersion $sigma$ of the cluster galaxies is often believed to be not only a straightforward but also robust test for the dynamical properties of galaxy clusters. Here, we present the $sigma$-$T$ relationship using the 94 clusters drawn from the largest sample of 149 clusters in literature, for which both $sigma$ and $T$ are observationally determined. Employment of the doubly weighted orthogonal distance regression to our sample yields $sigma=10^{2.47pm0.06}T^{0.67pm0.09}$, indicating an apparent deviation of dynamical state from that predicted by the isothermal and hydrostatic equilibrium model for galaxy clusters, though the average ratio $eta_{spec}$ of specific energy in galaxies to that in gas is found to be in excellent agreement with unity. It shows that a nonisothermal gas distribution with a mean polytropic index of $gamma=1.3$ can account for the reported $sigma$-$T$ relationship, while overall clusters can still be regarded as dynamically-relaxed systems. | | Source: | arXiv, astro-ph/9808181 | | Services: | Forum | Review | PDF | Favorites | |
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