Dormant dwarf spheroidal galaxies, deactivated by Type Ia supernovae

Abstract

Some dwarf spheroidal galaxies have experienced many Gyrs long periods without star formation. We show that Type Ia supernovae, formed from a first generation of stars, can delay a second epoch of star formation by several Gyrs, if the total gas mass in the dwarf spheroidals is smaller than $10^8 M_{\odot}$. The details depend on the assumed Type Ia supernova model and the mass fraction of stars formed in the first population. This scenario requires that dwarf spheroidals be confined by dark matter halos, as otherwise the heated gas would have been lost due to tidal effects and galactic winds. If Type Ia supernovae played an important role, heating the gas in dwarf spheroidals, they should also have increased their iron abundance during the epoch without star formation. The subsequent stellar generation should then start with a higher [Fe/H] than that of the most iron-rich stars found in the previous generation.