Journal
ASTROPHYSICAL JOURNAL LETTERS
Volume 739, Issue 2, Pages -Publisher
IOP PUBLISHING LTD
DOI: 10.1088/2041-8205/739/2/L47
Keywords
galaxies: formation; galaxies: fundamental parameters; galaxies: halos; galaxies: kinematics and dynamics; galaxies: spiral; galaxies: stellar content
Categories
Funding
- LKBF
- Netherlands Research School for Astronomy and University of Wisconsin Ciriacks Faculty
- [NSF/AST-9618849]
- [997078]
- [0307417]
- [0607516]
- [1009491]
- [NSF/OISE-0754437]
- [Spitzer GO-30894]
- [NWO/614.000.807]
- Division Of Astronomical Sciences
- Direct For Mathematical & Physical Scien [1009471] Funding Source: National Science Foundation
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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 (sigma(disk)(z,R=0)) is related to the maximum rotation speed (V-max) as sigma(disk)(z,R=0) similar to 0.26V(max), consistent with previous measurements for edge-on disk galaxies and a mean stellar velocity ellipsoid axial ratio alpha sigma(z)/sigma(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 (h(R)), 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 h(R) even for the most extreme, fast-rotating disks (V-max >= 300 km s(-1)) of the reddest rest frame, face-on color (B - K similar to 4 mag), and highest luminosity (M-K < -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.
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