NASA/IPAC EXTRAGALACTIC DATABASE
Date and Time of the Query: 2019-03-26 T05:06:41 PDT
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For refcode 2015MNRAS.450.4207B:
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Copyright by Royal Astronomical Society. 2015MNRAS.450.4207B The imprint of reionization on the star formation histories of dwarf galaxies Benitez-Llambay, A.; Navarro, J. F.; Abadi, M. G.; Gottlober, S.; Yepes, G.; Hoffman, Y.; Steinmetz, M. Abstract. We use a compilation of star formation histories (SFHs) and cosmological simulations to explore the impact of cosmic reionization on nearby isolated dwarf galaxies. Nearby dwarfs show a wide diversity of SFHs; from ancient systems that completed their star formation (SF) ~10 Gyr ago to young dwarfs that formed the majority of their stars in the past ~5 Gyr to 'two-component' systems characterized by the overlap of old and young stars. As an ensemble, SF in nearby dwarfs dips to lower-than-average rates at intermediate times (4 < t/Gyr < 8), a feature caused in the simulation by cosmic reionization. Reionization heats the gas and drives it out of low-mass haloes, affecting especially systems with virial temperatures of ~2 x 10^4^ K at z_reion_. SF begins before z_reion_ in systems above this threshold; its associated feedback compounds the effects of reionization, emptying the haloes of gas and leaving behind old stellar systems. In haloes below the threshold at z_reion_, reionization leads to a delay in the onset of SF that lasts until the halo grows massive enough to allow gas to cool and form stars, leading to a system with a prominent young stellar component. 'Two-component' systems may be traced to late accretion events that allow young stars to form in systems slightly above the threshold at z_reion_. The dearth of intermediate-age stars in nearby dwarfs might be the clearest signature of the imprint of cosmic reionization on the SFHs of dwarf galaxies. Key words: galaxies: dwarf, galaxies: evolution, galaxies: formation, Local Group, galaxies: stellar content, dark ages, reionization, first stars
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