Central Elemental Abundance Ratios in the Perseus Cluster: Resonant Scattering or SN Ia Enrichment?

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Abstract
We have determined abundance ratios in the core of the Perseus Cluster for several elements. These ratios indicate a central dominance of Type 1a supernova (SN Ia) ejecta similar to that found for A496, A2199, and A3571. Simultaneous analysis of ASCA spectra from SIS1, GIS2, and GIS3 shows that the ratio of Ni to Fe abundances is ~3.4 ± 1.1 times solar within the central 4'. This ratio is consistent with (and more precise than) that observed in other clusters whose central regions are dominated by SN Ia ejecta. Such a large Ni overabundance is predicted by "convective deflagration" explosion models for SNe Ia such as W7 but is inconsistent with delayed detonation models. We note that with current instrumentation the Ni Kα line is confused with Fe Kβ and that the Ni overabundance we observe has been interpreted by others as an anomalously large ratio of Fe Kβ to Fe Kα caused by resonant scattering in the Fe Kα line. We argue that a central enhancement of SN Ia ejecta and hence a high ratio of Ni to Fe abundances are naturally explained by scenarios that include the generation of chemical gradients by suppressed SN Ia winds or ram pressure stripping of cluster galaxies. It is not necessary to suppose that the intracluster gas is optically thick to resonant scattering of the Fe Kα line.
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