DORMANT DWARF SPHEROIDAL GALAXIES, DEACTIVATED BY TYPE IA SUPERNOVAE

Some dwarf spheroidal galaxies have experienced periods many Gyr long 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 Gyr, if the total gas mass in the dwarf spheroidals is sma ller than 10(8) M.. The details depend on the assumed Type Ia supernov a model and the mass fraction of stars formed in the first population. This scenario requires that dwarf spheroidals be confined by dark mat ter halos, since otherwise the heated gas would be lost due to tidal e ffects and galactic winds. If Type Ia supernovae play an important rol e, heating the gas in dwarf spheroidals, they should also increase the ir iron abundance during the epoch without star formation. The subsequ ent stellar generation should then start with a higher [Fe/H] than tha t of the most iron-rich stars found in the previous generation.