Extended X-Ray Emission from Early-Type Galaxies: Comparison with Optical

Abstract

In this poster we display the results from a detailed analysis of the distribution of the X-ray emission in early type galaxies. Two major results have come out of the analysis so far: a)The surface brightness radial profiles of isolated elliptical and SO galaxies are smoothly decreasing functions of radius out to a Rmax (similar to the optical radius). Outside Rmax a flattening in the slope is observed, although the exact shape of the profiles at large radii, where the data are poorest, cannot be determined at present.b)For R«Rmax, the X-ray and optical surface brightness profiles are similar (the nuclear region could be an exception). At larger radii, the X-ray profile could be flatter (NGC 4649 and NGC 4472 northern sector) or steeper (NGC 4472 southern sector) than the optical profile, or have a similar shape (NGC 4636).It is likely that the different profiles reflect the action of slightly different environments and/or a different ambient density around each galaxy, combined with the “history” of each galaxy. The tail in NGC 4472 could be the result of the motion of this galaxy in a dense intracluster medium. The X-ray deficiency in NGC 4649 could be due to either ram pressure stripping or the action of wind in the outer regions of the galaxy.