| Type |
Journal Article |
| Names |
Matthew A. Bershady, Thomas P. K. Martinsson, Marc A. W. Verheijen, Kyle B. Westfall, David R. Andersen, Rob A. Swaters |
| Publication |
The Astrophysical Journal Letters |
| Volume |
739 |
| Issue |
2 |
| Pages |
L47 |
| Date |
October 1, 2011 |
| URL |
http://adsabs.harvard.edu/abs/2011ApJ...739L..47B |
| Library Catalog |
NASA ADS |
| Abstract |
We measure the contribution of galaxy disks to the overall gravitational potential of 30 nearly face-on intermediate-to-late-type spirals from the DiskMass Survey. The central vertical velocity dispersion of the disk stars (σdisk z, R = 0) is related to the maximum rotation speed (V max) as σdisk z, R = 0 ~ 0.26V max, consistent with previous measurements for edge-on disk galaxies and a mean stellar velocity ellipsoid axial ratio α ≡ σ z /σ R = 0.6. For reasonable values of disk oblateness, this relation implies these galaxy disks are submaximal. We find disks in our sample contribute only 15%-30% of the dynamical mass within 2.2 disk scale lengths (hR ), with percentages increasing systematically with luminosity, rotation speed, and redder color. These trends indicate that the mass ratio of disk-to-total matter remains at or below 50% at 2.2 hR even for the most extreme, fast-rotating disks (V max >= 300 km s-1) of the reddest rest frame, face-on color (B - K ~ 4 mag), and highest luminosity (MK < -26.5 mag). Therefore, spiral disks in general should be submaximal. Our results imply that the stellar mass-to-light ratio and hence the accounting of baryons in stars should be lowered by at least a factor of three. |
| Tags |
GALAXIES: FUNDAMENTAL PARAMETERS, GALAXIES: STELLAR CONTENT, Galaxies: Halos, galaxies: formation, galaxies: kinematics and dynamics, galaxies: spiral |