ASCA observation of the poor cluster of galaxies AWM 7: Evidence of an abundance increase in the intra-cluster medium at the center

We present the results of the ASCA central-pointing observation of the poor cD cluster AWM 7. The Performance Verification phase data of GIS 2; GIS 3, SIS 0 chip 1, and SIS 1 chip 3 were used to study the properties of the intra-cluster medium (ICM) within 16' around the X-ray centroid. We found that, compared with the outer regions, the equivalent width of the Fe-K lines increases in the central 4' (similar to 123 h(50)(-1) kpc) region by a factor of similar to 1.5. Although the ICM temperature tends to decrease in the same region, the observed increase in the Fe-K line equivalent width cannot be explained away by a possible temperature drop. The model fitting indicates that the abundance increases from similar to 0.4 solar outside 4' to similar to 0.6 solar at the center. Thus, after the Centaurus cluster and the Virgo cluster, AWM 7 is the third poor cD cluster confirmed to show an abundance increase in the central region. The 0.5-3 keV flux of the cool emission within 4' is constrained to be < 8 x 10(42) h(50)(-2) erg s(-1), or < 21% of the total 0.5-3 keV flux from the same so spatial region. We discuss possible relations of these phenomena to the cD galaxy.