Metallicity Gradients in the Intracluster Gas of Abell 496

Analysis of spatially resolved ASCA spectra of the intracluster gas in Abell 496 confirms there are mild metal abundance enhancements near the center, as previously found by White et al. (1994) in a joint analysis of Ginga LAC and Einstein SSS spectra. Simultaneous analysis of spectra from all ASCA instruments (SIS + GIS) shows that the iron abundance is 0.36 ± 0.03 solar 3− 12′ from the center of the cluster and rises ∼50% to 0.53± 0.04 solar within the central 2′. Nickel and sulfur abundances are also centrally enhanced. We use a variety of elemental abundance ratios to assess the relative contribution of SN Ia and SN II to the metal enrichment of the intracluster gas. We find marginal evidence of gradients in some abundance ratios, which indicate that the fraction of iron from SN Ia increases toward the cluster center. We estimate that SN Ia account for ∼46% of the iron mass 3− 12′ from the center and ∼72% within 2′. The increased proportion of SN Ia ejecta at the center is such that the central iron abundance enhancement can be attributed wholly to SN Ia; we find no significant gradient in SN II ejecta. We argue that the additional SN Ia ejecta near the center is the vestige of a secondary wind phase driven by SN Ia (following a more vigorous protogalactic wind driven by SN II), which was partially smothered in the cD due to its location at the cluster center. We argue against the central abundance enhancement being due to ram pressure stripping of gas from cluster galaxies, or to secularly accumulated stellar mass loss within the central cD, or to a radially declining ratio of early-type galaxy luminosity density to intracluster gas density. Subject headings: galaxies: abundances — galaxies: clusters: individual (Abell 496) — intergalactic medium — X-rays: galaxies