The Baryonic Tully-Fisher Relation of Galaxies with Extended Rotation Curves and the Stellar Mass of Rotating Galaxies

Abstract

I investigate the Baryonic Tully-Fisher relation for a sample of galaxies with extended 21 cm rotation curves spanning the range 20 < Vf < 300 km/s. A variety of scalings of the stellar mass-to-light ratio are considered. For each prescription for M/L, I give fits of the form Md = A Vf^x. Presumably, the prescription that comes closest to the correct value will minimize the scatter in the relation. The fit with minimum scatter has A = 50 solar masses/(km/s)^4 and x = 4. This relation holds over five decades in mass. Galaxy color, stellar fraction, and M/L are correlated with each other and with Md, in the sense that more massive galaxies tend to be more evolved. There is a systematic dependence of the degree of maximality of disks on surface brightness. High surface brightness galaxies typically have M/L ~ 3/4 of the maximum disk value, while low surface brightness galaxies typically attain ~ 1/4 of this amount.