Star Formation Histories of Ultra-Faint Dwarf Galaxies: environmental differences between Magellanic and non-Magellanic satellites?

Abstract

We present the color-magnitude diagrams and star formation histories (SFHs) of seven ultra-faint dwarf galaxies: Horologium 1, Hydra 2, Phoenix 2, Reticulum 2, Sagittarius 2, Triangulum 2, and Tucana 2, derived from high-precision Hubble Space Telescope photometry. We find that the SFH of each galaxy is consistent with them having created at least 80% of the stellar mass by $z\sim 6$. For all galaxies, we find quenching times older than 11.5 Gyr ago, compatible with the scenario in which reionization suppresses the star formation of small dark matter halos. However, our analysis also reveals some differences in the SFHs of candidate Magellanic Cloud satellites, i.e., galaxies that are likely satellites of the Large Magellanic Cloud and that entered the Milky Way potential only recently. Indeed, Magellanic satellites show quenching times about 600 Myr more recent with respect to those of other Milky Way satellites, on average, even though the respective timings are still compatible within the errors. This finding is consistent with theoretical models that suggest that satellites' SFHs may depend on their host environment at early times, although we caution that within the error bars all galaxies in our sample are consistent with being quenched at a single epoch.

7 pages, 3 figures, 2 tables. Accepted for publication in ApJL

References in corpus (14)

• Beasts of the Southern Wild: Discovery of nine Ultra Faint satellites in the vicinity of the Magellanic Clouds
• The Quenching of the Ultra-Faint Dwarf Galaxies in the Reionization Era
• Small Dwarf Galaxies Within Larger Dwarfs: Why Some Are Luminous While Most Go Dark
• The Star Formation Histories of Local Group Dwarf Galaxies II. Searching For Signatures of Reionization
• The Orbital Histories of Magellanic Satellites Using Gaia DR2 Proper Motions
• Hydra II: a faint and compact Milky Way dwarf galaxy found in the Survey of the Magellanic Stellar History
• Ultra-faint dwarfs in a Milky Way context: Introducing the Mint Condition DC Justice League Simulations
• The Star Formation Histories of Local Group Dwarf Galaxies III. Characterizing Quenching in Low-Mass Galaxies
• Isochrones for Old (> 5 Gyr) Stars and Stellar Populations. I. Models for $-2.4\le$ [Fe/H] $\le +0.6$, $0.25\le Y\le 0.33$, and $-0.4\le$ [$\alpha$\Fe] $\le +0.4$
• The cumulative star-formation histories of dwarf galaxies with TNG50. I: Environment-driven diversity and connection to quenching
• The binary fraction of stars in dwarf galaxies: the case of Leo II
• Comparing the Quenching Times of Faint M31 and Milky Way Satellite Galaxies
• The role of faint population III supernovae in forming CEMP stars in ultra-faint dwarf galaxies
• The Pristine Dwarf-Galaxy survey -- III. Revealing the nature of the Milky Way globular cluster Sagittarius II

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