Galactic bulge formation as a maximum intensity starburst

Abstract

Properties of normal galactic star formation, including the density dependence, threshold density, turbulent scaling relations, and clustering properties, are applied to the formation of galactic bulges. One important difference is that the bulge potential well is too deep to have allowed self-regulation or blowout by the pressures from young stars, unlike galactic disks or dwarf galaxies. As a result, bulge formation should have been at the maximum rate, which is such that most of the gas would get converted into stars in only a few dynamical timescales, or ∼ 108 yr. The gas accretion phase can be longer than this, but once the critical density is reached, which depends primarily on the total virial density from dark matter, the formation of stars in the bulge should be extremely rapid. Such three-dimensional star formation should also have formed many clusters, like normal disk star formation today. Some of these clusters may have survived as old globulars, but most were dispersed, although they might still be observable as concentrated streams in phase space.