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

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.

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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.

Item Type:Article
Related URLs:
URLURL TypeDescription Paper
Sacchi, Elena0000-0001-5618-0109
Kallivayalil, Nitya0000-0002-3204-1742
van der Marel, Roeland0000-0001-7827-7825
Libralato, Mattia0000-0001-9673-7397
Zivick, Paul0000-0001-9409-3911
Besla, Gurtina0000-0003-0715-2173
Brown, Thomas M.0000-0002-1793-9968
Choi, Yumi0000-0003-1680-1884
Deason, Alis0000-0001-6146-2645
Fritz, Tobias0000-0002-3122-300X
Geha, Marla0000-0002-7007-9725
Guhathakurta, Puragra0000-0001-8867-4234
Jeon, Myoungwon0000-0001-6529-9777
Kirby, Evan0000-0001-6196-5162
Majewski, Steven R.0000-0003-2025-3147
Patel, Ekta0000-0002-9820-1219
Simon, Joshua D.0000-0002-4733-4994
Sohn, Sangmo Tony0000-0001-8368-0221
Tollerud, Erik0000-0002-9599-310X
Wetzel, Andrew0000-0003-0603-8942
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
Funding AgencyGrant Number
Heising-Simons FoundationScialog Award
Hellman FellowshipUNSPECIFIED
Cottrell Scholar of Research CorporationUNSPECIFIED
NASANAS 5-26555
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)
Record Number:CaltechAUTHORS:20211014-170553664
Persistent URL:
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
Deposited By: George Porter
Deposited On:18 Oct 2021 22:53
Last Modified:18 Oct 2021 22:53

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