On dwarf galaxy scales, the different shapes of the galaxy stellar mass function and the dark halo mass function require a star-formation efficiency (SFE) in these systems that is currently more than 1 dex lower than that of Milky Way-size halos. Here, we argue that this trend may actually be reversed at high redshift. Specifically, by combining the resolved star-formation histories of nearby isolated dwarfs with the simulated mass-growth rates of dark matter halos, we show that the assembly of these systems occurs in two phases: (1) an early, fast halo accretion phase with a rapidly deepening potential well, characterized by a high SFE; and (2) a late, slow halo accretion phase where, perhaps as a consequence of reionization, the SFE is low. Nearby dwarfs have more old stars than predicted by assuming a constant or decreasing SFE with redshift, a behavior that appears to deviate qualitatively from the trends seen among more massive systems. Taken at face value, the data suggest that at sufficiently early epochs, dwarf galaxy halos above the atomic cooling mass limit can be among the most efficient sites of star formation in the universe.

Madau, P., Weisz, D., Conroy, C. (2014). Reversal of fortune: Increased star formation efficiencies in the early histories of dwarf galaxies?. THE ASTROPHYSICAL JOURNAL LETTERS, 790(2) [10.1088/2041-8205/790/2/L17].

Reversal of fortune: Increased star formation efficiencies in the early histories of dwarf galaxies?

Madau, P;
2014

Abstract

On dwarf galaxy scales, the different shapes of the galaxy stellar mass function and the dark halo mass function require a star-formation efficiency (SFE) in these systems that is currently more than 1 dex lower than that of Milky Way-size halos. Here, we argue that this trend may actually be reversed at high redshift. Specifically, by combining the resolved star-formation histories of nearby isolated dwarfs with the simulated mass-growth rates of dark matter halos, we show that the assembly of these systems occurs in two phases: (1) an early, fast halo accretion phase with a rapidly deepening potential well, characterized by a high SFE; and (2) a late, slow halo accretion phase where, perhaps as a consequence of reionization, the SFE is low. Nearby dwarfs have more old stars than predicted by assuming a constant or decreasing SFE with redshift, a behavior that appears to deviate qualitatively from the trends seen among more massive systems. Taken at face value, the data suggest that at sufficiently early epochs, dwarf galaxy halos above the atomic cooling mass limit can be among the most efficient sites of star formation in the universe.
Articolo in rivista - Articolo scientifico
dark matter; galaxies: dwarf; galaxies: halos; galaxies: star formation; galaxies: stellar content;
English
2014
790
2
L17
none
Madau, P., Weisz, D., Conroy, C. (2014). Reversal of fortune: Increased star formation efficiencies in the early histories of dwarf galaxies?. THE ASTROPHYSICAL JOURNAL LETTERS, 790(2) [10.1088/2041-8205/790/2/L17].
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/10281/452986
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