How Galaxy Orientation Affects Measurements of Bulge Velocity Dispersion and the Consequences for the M-Sigma Relation
Abstract
The scaling relation of central black hole mass and spheroid velocity dispersion (M-Sigma relation) is one of the best-known and tightest correlations regarding black holes and their host galaxies. There has been much scrutiny concerning the difficulty of obtaining accurate black hole measurements, and rightly so; however, it has been taken for granted that measurements of velocity dispersion are essentially straightforward. We examine five Milky Way-like disk galaxies from cosmological SPH simulations and find that line-of-sight effects due to galaxy orientation can affect the value of Sigma by up to 30%, and consequently black hole mass estimates by 0.6 - 1.0 dex. Face-on orientations correspond to systematically lower velocity dispersion measurements, while more edge-on orientations give higher velocity dispersions. This effect may account for some of the scatter in the locally measured M-Sigma relation.
- Publication:
-
American Astronomical Society Meeting Abstracts #223
- Pub Date:
- January 2014
- Bibcode:
- 2014AAS...22345304B