Updating the sigma -T relationship for galaxy clusters
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(2.47+/-0.06}T({0.67+/-0.09)) , indicating an apparent deviation of dynamical state from that predicted by the isothermal and hydrostatic equilibrium model for galaxy clusters, though the average ratio beta_ {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. Table~1 is only available in electronic form at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsweb.u-strasbg.fr/Abstract.html
- Publication:
-
Astronomy and Astrophysics
- Pub Date:
- October 1998
- DOI:
- 10.48550/arXiv.astro-ph/9808181
- arXiv:
- arXiv:astro-ph/9808181
- Bibcode:
- 1998A&A...338..813W
- Keywords:
-
- GALAXIES: CLUSTERS: GENERAL;
- X-RAYS: GALAXIES;
- Astrophysics
- E-Print:
- 6 pages + 6 figures + 2 tables, A&