Dark and visible matter in spiral galaxies.
Abstract
Exploiting relevant information from the profiles of rotation curves, we calculate the dark-to-luminous mass ratio within the disc size for a sample of 43 spiral galaxies. The values we find, while proving the ubiquitous presence of dark matter, vary with luminosity. Faint and bright galaxies are found to be respectively halo- and disc-dominated in the disc regions. The luminosity sequence turns out to be a dark-to-luminous sequence. The Tully-Fisher correlation is justified as connected with the equilibrium condition of a thin disc embedded in a spherical halo. The dynamical effect of dark matter does not disrupt such a centrifugal equilibrium, because the dark-matter mass fraction is a smooth function of luminosity. By removing the dark-matter contribution from the velocity at the disc edge, the dispersion affecting the luminosity-kinematics relation is dramatically decreased as compared with the conventional Tully-Fisher correlation ({DELTA}δ ~0.3 mag). Comparison with stellar evolution models shows that the dynamically computed (M/L_B_)_disc_ ratios are able to explain the colours of spiral galaxies in a scenario involving a 10-Gyr star-formation phase with H_0_=75 km s^-1^ Mpc^-1^.
- Publication:
-
Monthly Notices of the Royal Astronomical Society
- Pub Date:
- September 1988
- DOI:
- 10.1093/mnras/234.1.131
- Bibcode:
- 1988MNRAS.234..131P
- Keywords:
-
- Dark Matter;
- Mass To Light Ratios;
- Rotating Matter;
- Spiral Galaxies;
- Astronomical Photometry;
- Brightness Distribution;
- Star Formation;
- Stellar Evolution;
- Astrophysics