Identifying X-ray Sources in Bulge and Disk Galaxies
Abstract
Nearby spiral galaxies contain a multitude of X-ray sources beautifully resolved by Chandra. In disk galaxies the X-ray sources follow the spiral arms, however in bulges they tend to cluster around a central source. By analogy with X-ray sources in the Milky Way and Local Group galaxies, we would expect the bulge sources to be low mass X-ray binaries and the sources in disk galaxies to be high mass X-ray binaries and possibly supernova remnants. This is consistent with what is seen, but is yet to be confirmed by Chandra. We examine the X-ray colors of sources in a sample of nearby spiral galaxies observed with Chandra. We look for differences in the X-ray colors of bulge and disk sources which may be indicative of different classes of binaries. Preliminary results show that the X-ray colors of many sources (in both bulges and disks) are consistent with a power law spectrum with absorption. Several sources have very hard X-ray colors and may be background sources, or possibly black hole candidates in a low, hard, state. We also find a population of soft sources in disk galaxies. These soft sources may be harder to detect in spiral bulges were there is more diffuse emission, or they may be genuinely under-abundant in bulges compared to disks. The implications of these results will be discussed. Support for this program comes from the Chandra X-ray Center under NASA Contract NAS8-39073 and GO1-2092A.
- Publication:
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American Astronomical Society Meeting Abstracts
- Pub Date:
- December 2001
- Bibcode:
- 2001AAS...199.1901P