Suzaku Observation of the Metallicity Distribution in the Intracluster Medium of the Fornax Cluster

The metallicity distribution in the Fornax cluster was studied with the XISinstrument onboard the Suzaku satellite. K-shell lines of O and Mg wereresolved clearly, and the abundances of O, Mg, Si, S and Fe were measured withgood accuracy. The region within a 4' radius of NGC 1399 shows approximatelysolar abundances of Fe, Si and S, while the O/Fe and Mg/Fe abundance ratios areabout 0.4--0.5 and 0.7 in solar units. In the outer region spanning radiibetween 6' and 23', the Fe and Si abundances drop to 0.4--0.5 solar and show nosignificant gradient within this region. The abundance ratios, O/Fe and Mg/Fe,are consistent with those in the central region. We also measured the Feabundance around NGC 1404 to be approximately solar, and the O, Ne and Mgabundances to be 0.5--0.7 times the Fe level. The significant relativeenhancement of Fe within 130 kpc of NGC 1399 and in NGC 1404 indicates anorigin in SN Ia, in contrast to the species O, Ne, and Mg which reflect thestellar metallicity. The mass-to-light ratios for O and Fe within 130 kpc ofNGC 1399 are over an order of magnitude lower than those in rich clusters,reflecting the metal enrichment history of this poor cluster.Comment: 13 pages, accepted to PAS