Constraining supernova models using the hot gas in clusters of galaxies

¹ SRON Netherlands Institute for Space Research, Sorbonnelaan 2, 3584 CA Utrecht, The Netherlands e-mail: j.de.plaa@sron.nl
² Astronomical Institute, Utrecht University, PO Box 80000, 3508 TA Utrecht, The Netherlands

Received: 12 September 2006
Accepted: 17 January 2007

Abstract

Context.The hot X-ray emitting gas in clusters of galaxies is a very large repository of metals produced by supernovae. During the evolution of clusters, billions of supernovae eject their material into this Intra-Cluster Medium (ICM).

Aims.We aim to accurately measure the abundances in the ICM of many clusters and compare these data with metal yields produced by supernovae. With accurate abundances determined using this cluster sample we will be able to constrain supernova explosion mechanisms.

Methods.Using the data archive of the XMM-Newton X-ray observatory, we compile a sample of 22 clusters. We fit spectra extracted from the core regions and determine the abundances of silicon, sulfur, argon, calcium, iron, and nickel. The abundances from the spectral fits are subsequently fitted to supernova yields determined from several supernova type Ia and core-collapse supernova models.

Results.We find that the argon and calcium abundances cannot be fitted with currently favoured supernova type Ia models. We obtain a major improvement of the fit, when we use an empirically modified delayed-detonation model that is calibrated on the Tycho supernova remnant. The two modified parameters are the density where the sound wave in the supernova turns into a shock and the ratio of the specific internal energies of ions and electrons at the shock. Our fits also suggest that the core-collapse supernovae that contributed to the enrichment of the ICM had progenitors which were already enriched.

Conclusions.The Ar/Ca ratio in clusters is a good touchstone for determining the quality of type Ia models. The core-collapse contribution, which is about 50% and not strongly dependent on the IMF or progenitor metallicity, does not have a significant impact on the Ar/Ca ratio. The number ratio between supernova type Ia and core-collapse supernovae suggests that binary systems in the appropriate mass range are very efficient (~5–16%) in eventually forming supernova type Ia explosions.