NGC 4522: Gone With the Wind

Jeffrey Kenney

NGC 4522 is one of the best examples of ongoing ram-pressure stripping in the nearby Virgo Galaxy Cluster. The neutral hydrogen gas (contours) that typically fuels star formation in spiral galaxies has been pushed of of this galaxy by pressure from the multi-million-degree gas that pervades the Virgo cluster; the stars (greyscale) in this spiral galaxy are relatively undisturbed. Just beyond where gas has been pushed out of the disk, the stellar spectrum shows signs of a small, recent burst of star formation, perhaps caused by the pressure that this galaxy felt from the hot cluster gas when the neutral gas was stripped, approximately 100 million years ago. The optical spectrum of the outer stellar disk of this galaxy is similar to post-starburst "K+A" galaxies typically observed at high redshift (i.e. large distances), suggesting that some such K+A galaxies can be formed by stripping.