Feedback and the scaling relations of dwarf/LSB galaxies

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  • 20 October 2002
Abstract
We study the role of feedback in establishing the scaling relations of low surface brightness (LSB) or dwarf galaxies, as measured from the SDSS and in the Local Group. The galaxies with stellar masses in the broad range 6x10^5 <M*< 3x10^10 Msun show tight correlations of internal velocity, metallicity and surface brightness (or radius) with stellar mass. These define a ``fundamental line" which distinguishes the LSBs from the brighter galaxies of high surface brightness (HSB). The relations for HSBs can be explained by spherical collapse to virial equilibrium of CDM haloes and angular-momentum conservation. The observed upper bound to LSBs coincides with the virial velocity of haloes in which supernova feedback could heat or remove much of the original gas, V10km/s, possibly due to the cooling barrier at T~10^4 K. We propose that the distinction between dwarf spheroidals (dE) and irregulars (dI) is due to radiative feedback associated with the cosmological reionization at z_ion~6. The dEs, typically of $V30km/s, the incomplete gas removal leads to gas-rich discs in which star formation is regulated by feedback.

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