Abstract

The Tully-Fisher relation (TFR) was studied for a sample of 2447 southern spiral galaxies observed by Mathewson et al. (1996). In addition, the central slopes of the rotation curves were determined for those galaxies in the sample that have Ha data available. The TFR for the sample was found to be M = -6.63 log Vmax -6.86 in Ha band and M = -8.41 logVmax -3.07 in HI band, different from M = -11.1 logVmax +2.04 obtained in previous studies (e.g., Rubin et al. 1985). The morphological class of galaxies has little to do with the slope of the TFR, and so do the maximum rotation velocities of the galaxies.

The central slope of the rotation curve, a good dynamical indicator of the mass concentration at the galactic center, was found to be in good agreement with the mass concentration suggested by the surface brightness measurements. Of the 178 galaxies that have a sharp brightness peak at the center, 80% have high central slopes in the rotation curves. The central slope of the rotation curve again has no correlation with the morphological class of the galaxies, nor does it depend on the absolute magnitude or maximum rotation velocity of a galaxy. These results were confirmed by independently examining 123 galaxies of the northern sky selected from various sources in the literature.
1999, for Intel ISEF

(Research processing)