A HIGH-RESOLUTION ROSAT X-RAY STUDY OF THE HERCULES CLUSTER

The well-studied, irregular Hercules cluster of galaxies (Abell 2151) was observed in X-rays with the ROSAT HRI. We find that the X-ray emis sion is concentrated toward the central subcluster of the system, in a greement with previous Einstein and ROSAT PSPC observations. The X-ray emission in this subcluster divides into two components, which corres pond to two groups of galaxies in the region. The center of the bright est (western) X-ray component coincides with the brightest cluster gal axy (BCG) NGC 6041A, while there is an X-ray peak near the center of t he poorer eastern component that agrees with the position of an ellipt ical radio galaxy NGC 6047. The X-ray emission is fairly irregular, an d there are separate X-ray features associated with individual galaxie s including the BCG NGC 6041A. There are two X-ray clumps associated w ith an interacting peculiar galaxy pair NGC 6040A/B. Gas stripping fro m the galaxy pair has depleted about 80% of their neutral hydrogen con tents. In addition, the stripped gas may constitute a majority of the X-ray emitting gas in this region, which suggests that the gas strippi ng in this subcluster may be very efficient and is an important contri buting factor to the origin of the hot gas. The interaction of the int racluster gas with the radio galaxy NGC 6047 has also been investigate d. A cooling flow of M = 143 +/- 28 M(.) yr(-1) is found in the centra l subcluster that may have deposited a significant fraction of the coo led gas to the central BCG galaxy NGC 6041A. We also probed the dynami c structure and dark matter distribution in the central subcluster. Ou r data show that, within the central 678 kpc, total dark matter in thi s main subcluster is comparable to the total material contained in lum inous galaxies and X-ray emitting gas in the region. Throughout the pa per, we have assumed a Hubble constant of 50 km s(-1) Mpc(-1) and q(0) = 0.5.