X-ray and Ultraviolet Halos Around the Nearby Edge-on Spiral NGC 891
Abstract
The origin of the hot and cold halos seen around many spiral galaxies is an important unknown in galaxy evolution because of the two leading, and very different hypotheses. Halos could either be material accreted from the circumgalactic medium or matter ejected from the disk by a "galactic fountain" of ongoing supernova activity. We examine these formation scenarios with a multiwavelength study of NGC 891, a nearby edge-on Milky Way analog with a giant HI halo and bright X-ray halo that now has very high quality data across the spectrum, including new deep XMM-Newton and Swift UVOT exposures in addition to existing HI, radio continuum, IR, and optical datasets. We argue that the halo does not neatly fit into either picture and may be a composite of accreted and expelled material, and discuss the implications for galaxy halos in general.
- Publication:
-
AAS/High Energy Astrophysics Division #13
- Pub Date:
- April 2013
- Bibcode:
- 2013HEAD...1330106H