Xray study of the dynamical properties of photometrically selected galaxy clusters
Full text  
Author(s): 
Total Authors: 3

Affiliation:  ^{[1]} Univ Sao Paulo, Inst Astron Geofis & Ciencias Atmosfer, Dept Astron, BR05508900 Sao Paulo  Brazil
Total Affiliations: 1

Document type:  Journal article 
Source:  Astronomy & Astrophysics; v. 510, FEB 2010. 
Web of Science Citations:  25 
Abstract  
Aims. Given that in most cases just thermal pressure is taken into account in the hydrostatic equilibrium equation to estimate galaxy cluster mass, the main purpose of this paper is to consider the contribution of all three nonthermal components to total mass measurements. The nonthermal pressure is composed by cosmic rays, turbulence and magnetic pressures. Methods. To estimate the thermal pressure we used public XMMNewton archival data of five Abell clusters to derive temperature and density profiles. To describe the magnetic pressure, we assume a radial distribution for the magnetic field, B(r) proportional to rho(alpha)(g). To seek generality we assume alpha within the range of 0.5 to 0.9, as indicated by observations and numerical simulations. Turbulent motions and bulk velocities add a turbulent pressure, which is considered using an estimate from numerical simulations. For this component, we assume an isotropic pressure, P(turb) = 1/3 rho(g)(sigma(2)(r) + sigma(2)(t)). We also consider the contribution of cosmic ray pressure, P(cr) proportional to r(0.5). Thus, besides the gas (thermal) pressure, we include these three nonthermal components in the magnetohydrostatic equilibrium equation and compare the total mass estimates with the values obtained without them. Results. A consistent description for the nonthermal component could yield a variation in mass estimates that extends from 10% to similar to 30%. We verified that in the inner parts of cool core clusters the cosmic ray component is comparable to the magnetic pressure, while in noncool core clusters the cosmic ray component is dominant. For cool core clusters the magnetic pressure is the dominant component, contributing more than 50% of the total mass variation due to nonthermal pressure components. However, for noncool core clusters, the major influence comes from the cosmic ray pressure that accounts for more than 80% of the total mass variation due to nonthermal pressure effects. For our sample, the maximum influence of the turbulent component to the total mass variation can be almost 20%. Although all of the assumptions agree with previous works, it is important to notice that our results rely on the specific parametrization adopted in this work. We show that this analysis can be regarded as a starting point for a more detailed and refined exploration of the influence of nonthermal pressure in the intracluster medium (ICM). (AU)  
FAPESP's process:  06/582403  Planetary nebulae and central stars: stellar winds and metallicity 
Grantee:  Graziela Roswitha Keller Rodrigues 
Support type:  Scholarships in Brazil  Doctorate 
FAPESP's process:  08/043187  Intracluster gas enrichment ánd star formation efficiency ín clusters of galaxies 
Grantee:  Tatiana Ferraz Laganá 
Support type:  Scholarships in Brazil  PostDoctorate 