X-RAY EVIDENCE FOR THE INTERACTION OF THE GIANT ELLIPTIC GALAXY NGC-4472 WITH ITS VIRGO CLUSTER ENVIRONMENT

We analyze X-ray spatial and spectral data on the giant elliptical gal axy NGC 4472, the brightest galaxy in the Virgo cluster. The X-ray con tours of NGC 4472 are elongated in the northeast-southwest direction, perhaps as a result of motion through the Virgo intracluster gas. A bo w shock-like structure is evident on the galaxy's north side. The temp erature at a given radius in this bow shock region is slightly higher than the temperature at the same radius on the galaxy's southwest side . Away from this bow shock region, the surface brightness profile of N GC 4472 can be traced out to a radius of 260 kpc in the southwest dire ction. Beyond 260 kpc, we find evidence for emission from both the Vir go cluster and the Galactic North Polar Spur (believed to be the rim o f a hot Galactic superbubble). NGC 4472 is interacting with the dwarf irregular galaxy UGC 7636. We do not detect any excess or deficit in t he X-ray emission toward this galaxy. An H I cloud, detected previousl y in the 21 cm line and located midway between the two galaxies, appea rs to have been removed from the irregular galaxy through either tidal interaction or ram pressure stripping. We find a marginally significa nt hole in the ROSAT HRI and PSPC X-ray images at the position of this cloud, suggesting that the cloud lies at the front side of NGC 4472. If the hole in the X-ray images is due to soft X-ray absorption, the t otal gaseous mass of the cloud must be at least 1.7 x 10(9) M., far gr eater than its 21 cm H I mass. This suggests that the majority of the material in the cloud is molecular.