Feedback and the fundamental line of low-luminosity low-surface-brightness/dwarf galaxies

Abstract

We study in simple terms the role of feedback in establishing the scaling relations of low-surface-brightness (LSB) and dwarf galaxies with stellar masses in the range 6 × 10 5 ≤ M * ≤ 3 x 10 1 0 M O . . These galaxies - as measured, for example, from the Sloan Digital Sky Survey (SDSS) and in the Local Group - show tight correlations of internal velocity, metallicity and surface brightness (or radius) with M * . They define a fundamental line which distinguishes them from the brighter galaxies of high surface brightness and metallicity. The idealized model assumes spherical collapse of cold dark matter (CDM) haloes to virial equilibrium and angular momentum conservation. The relations for bright galaxies are reproduced by assuming that M * is a constant fraction of the halo mass M. The upper bound to the low-luminosity LSBs coincides with the virial velocity of haloes in which supernova feedback could significantly suppress star formation, V 30 km s - 1 , retain gas-rich discs with feedback-regulated star formation.