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Star Formation Histories of Ultra-faint Dwarf Galaxies: Environmental Differences between Magellanic and Non-Magellanic Satellites?*

Sacchi, Elena; Richstein, Hannah; Kallivayalil, Nitya; van der Marel, Roeland; Libralato, Mattia; Zivick, Paul; Besla, Gurtina; Brown, Thomas M.; Choi, Yumi; Deason, Alis; Fritz, Tobias; Geha, Marla; Guhathakurta, Puragra; Jeon, Myoungwon; Kirby, Evan; Majewski, Steven R.; Patel, Ekta; Simon, Joshua D.; Tony Sohn, Sangmo; Tollerud, Erik; Wetzel, Andrew

Star Formation Histories of Ultra-faint Dwarf Galaxies: Environmental Differences between Magellanic and Non-Magellanic Satellites?* Thumbnail


Authors

Elena Sacchi

Hannah Richstein

Nitya Kallivayalil

Roeland van der Marel

Mattia Libralato

Paul Zivick

Gurtina Besla

Thomas M. Brown

Yumi Choi

Tobias Fritz

Marla Geha

Puragra Guhathakurta

Myoungwon Jeon

Evan Kirby

Steven R. Majewski

Ekta Patel

Joshua D. Simon

Sangmo Tony Sohn

Erik Tollerud

Andrew Wetzel



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 highprecision 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 ∼ 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.

Citation

Sacchi, E., Richstein, H., Kallivayalil, N., van der Marel, R., Libralato, M., Zivick, P., …Wetzel, A. (2021). Star Formation Histories of Ultra-faint Dwarf Galaxies: Environmental Differences between Magellanic and Non-Magellanic Satellites?*. Astrophysical Journal Letters, 920(1), Article L19. https://doi.org/10.3847/2041-8213/ac2aa3

Journal Article Type Article
Acceptance Date Sep 27, 2021
Online Publication Date Oct 8, 2021
Publication Date Oct 10, 2021
Deposit Date Nov 23, 2021
Publicly Available Date Nov 23, 2021
Journal The Astrophysical Journal Letters
Print ISSN 2041-8205
Electronic ISSN 2041-8213
Publisher American Astronomical Society
Peer Reviewed Peer Reviewed
Volume 920
Issue 1
Article Number L19
DOI https://doi.org/10.3847/2041-8213/ac2aa3

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Copyright Statement
© 2021. The American Astronomical Society. All rights reserved.





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