Sacchi, Elena and Richstein, Hannah and Kallivayalil, Nitya and van der Marel, Roeland and Libralato, Mattia and Zivick, Paul and Besla, Gurtina and Brown, Thomas M. and Choi, Yumi and Deason, Alis and Fritz, Tobias and Geha, Marla and Guhathakurta, Puragra and Jeon, Myoungwon and Kirby, Evan and Majewski, Steven R. and Patel, Ekta and Simon, Joshua D. and Sohn, Sangmo Tony and Tollerud, Erik and Wetzel, Andrew (2021) Star Formation Histories of Ultra-faint Dwarf Galaxies: Environmental Differences between Magellanic and Non-Magellanic Satellites? Astrophysical Journal Letters, 920 (1). Art. No. 19. ISSN 2041-8205. doi:10.3847/2041-8213/ac2aa3. https://resolver.caltech.edu/CaltechAUTHORS:20211014-170553664
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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 ∼ 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.
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Additional Information: | © 2021. The American Astronomical Society. Received 2021 August 9; revised 2021 September 27; accepted 2021 September 27; published 2021 October 8. These data are associated with the HST Treasury Program 14734 (PI Kallivayalil). Support for this program was provided by NASA through grants from the Space Telescope Science Institute. A.W. received support from NASA ATP grant Nos. 80NSSC18K1097 and 80NSSC20K0513; a Scialog Award from the Heising-Simons Foundation; and a Hellman Fellowship. This material is based upon work supported by the National Science Foundation under grant No. AST-1847909. E.N.K. gratefully acknowledges support from a Cottrell Scholar award administered by the Research Corporation for Science Advancement. Based on observations obtained with the NASA/ESA Hubble Space Telescope at the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy under NASA Contract NAS 5-26555. | ||||||||||||||||||||||||||||||||||||||||||
Group: | Astronomy Department | ||||||||||||||||||||||||||||||||||||||||||
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Subject Keywords: | Dwarf galaxies; Galaxy evolution; Galaxy dynamics; Galaxy stellar content; Galaxy kinematics; Star formation; Local Group; Magellanic Clouds | ||||||||||||||||||||||||||||||||||||||||||
Issue or Number: | 1 | ||||||||||||||||||||||||||||||||||||||||||
Classification Code: | Unified Astronomy Thesaurus concepts: Dwarf galaxies (416); Galaxy evolution (594); Galaxy dynamics (591); Galaxy stellar content (621); Galaxy kinematics (602); Star formation (1569); Local Group (929); Magellanic Clouds (990) | ||||||||||||||||||||||||||||||||||||||||||
DOI: | 10.3847/2041-8213/ac2aa3 | ||||||||||||||||||||||||||||||||||||||||||
Record Number: | CaltechAUTHORS:20211014-170553664 | ||||||||||||||||||||||||||||||||||||||||||
Persistent URL: | https://resolver.caltech.edu/CaltechAUTHORS:20211014-170553664 | ||||||||||||||||||||||||||||||||||||||||||
Official Citation: | Elena Sacchi et al 2021 ApJL 920 L19 | ||||||||||||||||||||||||||||||||||||||||||
Usage Policy: | No commercial reproduction, distribution, display or performance rights in this work are provided. | ||||||||||||||||||||||||||||||||||||||||||
ID Code: | 111434 | ||||||||||||||||||||||||||||||||||||||||||
Collection: | CaltechAUTHORS | ||||||||||||||||||||||||||||||||||||||||||
Deposited By: | George Porter | ||||||||||||||||||||||||||||||||||||||||||
Deposited On: | 18 Oct 2021 22:53 | ||||||||||||||||||||||||||||||||||||||||||
Last Modified: | 18 Oct 2021 22:53 |
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