An Unusual Discontinuity in the X‐Ray Surface Brightness Profile of NGC 507: Evidence of an Abundance Gradient?

We present results from a 45 ks Chandra/ACIS-I observation of the nearby($z=0.01646$) NGC 507 group. The X-ray surface brightness profile of the outerregion of the group is well described by an isothermal $\beta$-profileconsistent with earlier ROSAT observations. We find a sharp edge ordiscontinuity in the radial surface brightness profile 55 kpc E and SE of NGC507 covering a $\sim125^\circ$ arc. At the sharpest part of the discontinuity,the surface brightness declines by a factor of $\sim$2 over a distance of 6.9kpc ($\sim 15''$). The inner and outer gas temperatures across thediscontinuity differ by only about 0.2 keV (interior and exterior gastemperatures are 1.2 and 1.3 keV, respectively). Spectral analysis indicatesthat there is a large gradient in the elemental abundance across thediscontinuity, and comparison with the low resolution NVSS radio maps suggeststhat the discontinuity is aligned with a low surface brightness radio lobe. Weconclude that the appearance of this discontinuity is the result of thetransport of high abundance material from the center of the galaxy by theexpanding radio lobe, similar to structures seen in {\em Chandra} observationsof Perseus A and Hydra A.Comment: 15 pages, 6 figures, submitted to Astrophysical Journal Letter