METAL ABUNDANCE OF AN X-RAY EMITTING GAS IN 2 GROUPS OF GALAXIES - THE NGC-5044 GROUP AND HCG-51

We observed two groups of galaxies, the NGC 5044 group (WP 23) and Hic kson's compact group HCG 51, with ASCA. We detected an extended bright soft X-ray emission, which indicates the existence of large amounts o f a hot X-ray emitting gas in both targets. The temperature of the hot gas is similar to 1 keV for both objects, which is equivalent to thei r galaxy velocity dispersion. The metal abundance of the gas is 0.3-0. 5 solar value for both objects, which is similar to that of rich clust ers of galaxies. The Si to Fe abundance ratio is smaller than that of rich clusters of galaxies, although the iron abundances determined by the Fe-L lines are somewhat uncertain. The X-ray luminosities in the 0 .5-10 keV band are 1x10(43) erg s(-1) and 5x10(42) erg s(-1) for the N GC 5044 group and HCG 51, respectively, which are higher by an order o f magnitude than those of X-ray bright elliptical galaxies. This makes HCG 51 one of the most X-ray luminous compact groups. Both objects ha ve a total gravitating mass of M(total) similar to 2.0 x 10(13) M., an d a gas mass and a galaxy mass of M(gas) similar to M(galaxy) similar to 1.5 x 10(12) M.. The ratios among these mass components are M(gas)/ M(galaxy) similar to 1 and (M(gas)+M(galaxy))/M/total similar to 0.2 w ithin similar to 350 kpc for both objects. The latter is similar to pr evious ROSAT results for many groups of galaxies, while the former is larger than the average value of the ROSAT-observed groups. Moreover, the metal abundances of the present two groups are significantly highe r than those of the NGC 2300 group and HCG 62, and are comparable to t hose of clusters. These suggest that the hot-gas mass and metal abunda nces can scatter widely among groups, compared to the small variance f ound among rich clusters.