Avishai Dekel (Jerusalem University)
"The Role of Feedback in the Formation of LSB/Dwarf Galaxies"


I will address the role of feedback in establishing the scaling relations of LSB/dwarf galaxies, as confirmed by data from SDSS and in the Local Group dwarfs. These galaxies show tight correlations between the observables over 5 decades in stellar mass, which distinguish them from the brighter galaxies. The observed upper limit to the LSB range coincides with the limit of 100 km/s derived by Dekel \& Silk (1986, DS) for halos that can lose gas due to supernova feedback. Based on the DS estimate of the energy fed to the gas by supernovae ejecta subject to radiative loses, we obtain that it is proprtional to the stellar mass, and show that within the framework of galaxy formation in CDM halos this naturally leads to the observed scaling relations. We suggest that the lower bound of 10 km/s seen in dEs is due to the cooling barrier at $T \sim 104$K. We propose further that the dEs form their stars before the cosmological reionization at z=6 and that the associated radiative feedback is responsible for the absence of gas in dEs below 30 km/s, allowing the appearance of gas-rich, disky dIs in deeper potential wells.

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