The distribution of late-type (old) stars in the inner parsec of the Milky Way is very different than expected for a relaxed population around a supermassive black hole. Instead of a density cusp, there is a ̃0.5 pc core. This article discusses what sorts of dynamical models might explain this "conundrum of old age." A straightforward interpretation is that the nucleus is unrelaxed, and that the distribution of the old giants reflects the distribution of fainter stars and stellar remnants generally in the core. On the other hand, a density cusp could be present in the unobserved populations, and the deficit of bright giants could be a result of interactions with these objects. At the present time, no model is clearly preferred.
The Galactic Center: a Window to the Nuclear Environment of Disk Galaxies
- Pub Date:
- May 2011
- Astrophysics - Galaxy Astrophysics;
- Astrophysics - Cosmology and Extragalactic Astrophysics
- To appear in "The Galactic Center: A Window on the Nuclear Environment of Disk Galaxies", ed. Mark Morris, Daniel Q. Wang and Feng Yuan