An analysis of electron distributions in galaxy clusters by means of the flux ratio of iron lines FeXXV and XXVI

¹ Institut d'Astrophysique de Paris, CNRS, UMR 7095, Université Pierre et Marie Curie, 98bis Bd Arago, 75014 Paris, France e-mail: prokhoro@iap.fr
² Moscow Institute of Physics and Technology, Institutskii lane, 141700 Moscow Region, Dolgoprudnii, Russia
³ Lebedev Physical Institute, 117924 Moscow, Russia
⁴ ASI Science Data Center, ASDC c/o ESRIN, via G. Galilei 00044 Frascati, Italy
⁵ ASI, Viale Liegi 26, Roma, Italy
⁶ INAF - Osservatorio Astronomico di Roma, via Frascati 33, 00040 Monteporzio, Italy

Received: 6 October 2008
Accepted: 5 December 2008

Abstract

Aims. The interpretation of hard X-ray emission from galaxy clusters is still ambiguous and different proposed models can be probed using various observational methods. Here we explore a new method based on Fe-line observations.

Methods. Spectral-line emissivities have usually been calculated by assuming a Maxwellian electron distribution. In this paper, a generalized approach to calculating the iron-line flux for a modified Maxwellian distribution is considered.

Results. We calculated the flux ratio of iron lines for various possible populations of electrons proposed to account for measurements of hard X-ray excess-emission from the clusters A2199 and Coma. We found that the influence of the suprathermal electron population on the flux ratio is more significant in low temperature clusters (as Abell 2199) than in high temperature clusters (as Coma).