skip to main content
OSTI.GOV title logo U.S. Department of Energy
Office of Scientific and Technical Information

Title: GALAXY DISKS ARE SUBMAXIMAL

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 ({sigma}{sup disk} {sub z,R=0}) is related to the maximum rotation speed (V {sub max}) as {sigma}{sup disk} {sub z,R=0} {approx} 0.26V {sub max}, consistent with previous measurements for edge-on disk galaxies and a mean stellar velocity ellipsoid axial ratio {alpha} {identical_to} {sigma} {sub z}/{sigma} {sub 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{sub 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{sub R} even for the most extreme, fast-rotating disks (V {sub max} {>=} 300 km s{sup -1}) of the reddest rest frame, face-on color (B - K {approx} 4 mag), and highest luminosity (M{sub 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 accountingmore » of baryons in stars should be lowered by at least a factor of three.« less

Authors:
 [1]; ; ;  [2];  [3];  [4]
  1. Department of Astronomy, University of Wisconsin, 475 N. Charter St., Madison, WI 53706 (United States)
  2. Kapteyn Astronomical Institute, University of Groningen, Landleven 12, 9747 AD Groningen (Netherlands)
  3. NRC Herzberg Institute of Astrophysics, 5071 W Saanich Road, Victoria, BC V9E 2E7 (Canada)
  4. National Optical Astronomical Observatories, Tucson, AZ (United States)
Publication Date:
OSTI Identifier:
21565432
Resource Type:
Journal Article
Journal Name:
Astrophysical Journal Letters
Additional Journal Information:
Journal Volume: 739; Journal Issue: 2; Other Information: DOI: 10.1088/2041-8205/739/2/L47; Journal ID: ISSN 2041-8205
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; GALAXIES; MASS; ROTATION; STARS; VELOCITY; VISIBLE RADIATION; ELECTROMAGNETIC RADIATION; MOTION; RADIATIONS

Citation Formats

Bershady, Matthew A., Martinsson, Thomas P. K., Verheijen, Marc A. W., Westfall, Kyle B., Andersen, David R., and Swaters, Rob A., E-mail: mab@astro.wisc.edu. GALAXY DISKS ARE SUBMAXIMAL. United States: N. p., 2011. Web. doi:10.1088/2041-8205/739/2/L47.
Bershady, Matthew A., Martinsson, Thomas P. K., Verheijen, Marc A. W., Westfall, Kyle B., Andersen, David R., & Swaters, Rob A., E-mail: mab@astro.wisc.edu. GALAXY DISKS ARE SUBMAXIMAL. United States. doi:10.1088/2041-8205/739/2/L47.
Bershady, Matthew A., Martinsson, Thomas P. K., Verheijen, Marc A. W., Westfall, Kyle B., Andersen, David R., and Swaters, Rob A., E-mail: mab@astro.wisc.edu. Sat . "GALAXY DISKS ARE SUBMAXIMAL". United States. doi:10.1088/2041-8205/739/2/L47.
@article{osti_21565432,
title = {GALAXY DISKS ARE SUBMAXIMAL},
author = {Bershady, Matthew A. and Martinsson, Thomas P. K. and Verheijen, Marc A. W. and Westfall, Kyle B. and Andersen, David R. and Swaters, Rob A., E-mail: mab@astro.wisc.edu},
abstractNote = {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}{sup disk} {sub z,R=0}) is related to the maximum rotation speed (V {sub max}) as {sigma}{sup disk} {sub z,R=0} {approx} 0.26V {sub max}, consistent with previous measurements for edge-on disk galaxies and a mean stellar velocity ellipsoid axial ratio {alpha} {identical_to} {sigma} {sub z}/{sigma} {sub 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{sub 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{sub R} even for the most extreme, fast-rotating disks (V {sub max} {>=} 300 km s{sup -1}) of the reddest rest frame, face-on color (B - K {approx} 4 mag), and highest luminosity (M{sub 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.},
doi = {10.1088/2041-8205/739/2/L47},
journal = {Astrophysical Journal Letters},
issn = {2041-8205},
number = 2,
volume = 739,
place = {United States},
year = {2011},
month = {10}
}