The Astrophysical Journal (Jan 2023)
The Hubble Space Telescope Survey of M31 Satellite Galaxies. II. The Star Formation Histories of Ultrafaint Dwarf Galaxies
- Alessandro Savino,
- Daniel R. Weisz,
- Evan D. Skillman,
- Andrew Dolphin,
- Andrew A. Cole,
- Nitya Kallivayalil,
- Andrew Wetzel,
- Jay Anderson,
- Gurtina Besla,
- Michael Boylan-Kolchin,
- Thomas M. Brown,
- James S. Bullock,
- Michelle L. M. Collins,
- M. C. Cooper,
- Alis J. Deason,
- Aaron L. Dotter,
- Mark Fardal,
- Annette M. N. Ferguson,
- Tobias K. Fritz,
- Marla C. Geha,
- Karoline M. Gilbert,
- Puragra Guhathakurta,
- Rodrigo Ibata,
- Michael J. Irwin,
- Myoungwon Jeon,
- Evan N. Kirby,
- Geraint F. Lewis,
- Dougal Mackey,
- Steven R. Majewski,
- Nicolas Martin,
- Alan McConnachie,
- Ekta Patel,
- R. Michael Rich,
- Joshua D. Simon,
- Sangmo Tony Sohn,
- Erik J. Tollerud,
- Roeland P. van der Marel
Affiliations
- Alessandro Savino
- ORCiD
- Department of Astronomy, University of California , Berkeley, CA 94720, USA ; [email protected]
- Daniel R. Weisz
- ORCiD
- Department of Astronomy, University of California , Berkeley, CA 94720, USA ; [email protected]
- Evan D. Skillman
- ORCiD
- University of Minnesota , Minnesota Institute for Astrophysics, School of Physics and Astronomy, 116 Church Street, S.E., Minneapolis, MN 55455, USA
- Andrew Dolphin
- ORCiD
- Raytheon Technologies , 1151 E. Hermans Road, Tucson, AZ 85756, USA; Steward Observatory, University of Arizona , 933 N. Cherry Avenue, Tucson, AZ 85719, USA
- Andrew A. Cole
- ORCiD
- School of Natural Sciences, University of Tasmania , Private Bag 37, Hobart, Tasmania 7001, Australia
- Nitya Kallivayalil
- ORCiD
- Department of Astronomy, University of Virginia , 530 McCormick Road, Charlottesville, VA 22904, USA
- Andrew Wetzel
- ORCiD
- Department of Physics and Astronomy, University of California , Davis, CA 95616, USA
- Jay Anderson
- ORCiD
- Space Telescope Science Institute , 3700 San Martin Drive, Baltimore, MD 21218, USA
- Gurtina Besla
- ORCiD
- Department of Astronomy, University of Arizona , 933 N. Cherry Avenue, Tucson, AZ 85721, USA
- Michael Boylan-Kolchin
- ORCiD
- Department of Astronomy, The University of Texas at Austin , 2515 Speedway, Stop C1400, Austin, TX 78712, USA
- Thomas M. Brown
- ORCiD
- Space Telescope Science Institute , 3700 San Martin Drive, Baltimore, MD 21218, USA
- James S. Bullock
- ORCiD
- Department of Physics and Astronomy, University of California , Irvine, CA 92697 USA
- Michelle L. M. Collins
- ORCiD
- Physics Department, University of Surrey , Guildford GU2 7XH, UK
- M. C. Cooper
- ORCiD
- Department of Physics and Astronomy, University of California , Irvine, CA 92697 USA
- Alis J. Deason
- ORCiD
- Institute for Computational Cosmology, Department of Physics, Durham University , Durham DH1 3LE, UK
- Aaron L. Dotter
- Department of Physics and Astronomy, Dartmouth College , 6127 Wilder Laboratory, Hanover, NH 03755, USA
- Mark Fardal
- Eureka Scientific , 2452 Delmer Street, Suite 100, Oakland, CA 96402, USA
- Annette M. N. Ferguson
- ORCiD
- Institute for Astronomy, University of Edinburgh , Royal Observatory, Blackford Hill, Edinburgh EH9 3HJ, UK
- Tobias K. Fritz
- ORCiD
- Department of Astronomy, University of Virginia , Charlottesville, 530 McCormick Road, VA 22904-4325, USA
- Marla C. Geha
- ORCiD
- Department of Astronomy, Yale University , New Haven, CT 06520, USA
- Karoline M. Gilbert
- ORCiD
- Space Telescope Science Institute , 3700 San Martin Drive, Baltimore, MD 21218, USA; The William H. Miller III Department of Physics & Astronomy, Bloomberg Center for Physics and Astronomy, Johns Hopkins University , 3400 N. Charles Street, Baltimore, MD 21218, USA
- Puragra Guhathakurta
- ORCiD
- UCO/Lick Observatory, Department of Astronomy & Astrophysics, University of California Santa Cruz , 1156 High Street, Santa Cruz, CA 95064, USA
- Rodrigo Ibata
- ORCiD
- Observatoire de Strasbourg, 11, rue de l’Universite , F-67000 Strasbourg, France
- Michael J. Irwin
- ORCiD
- Institute of Astronomy, University of Cambridge , Cambridge CB3 0HA, UK
- Myoungwon Jeon
- School of Space Research, Kyung Hee University , 1732 Deogyeong-daero, Yongin-si, Gyeonggi-do 17104, Republic of Korea
- Evan N. Kirby
- ORCiD
- Department of Physics, University of Notre Dame , Notre Dame, IN 46556, USA
- Geraint F. Lewis
- ORCiD
- Sydney Institute for Astronomy, School of Physics, A28, The University of Sydney , NSW 2006, Australia
- Dougal Mackey
- ORCiD
- Research School of Astronomy and Astrophysics, Australian National University , Canberra 2611, ACT, Australia
- Steven R. Majewski
- ORCiD
- Department of Astronomy, University of Virginia , 530 McCormick Road, Charlottesville, VA 22904, USA
- Nicolas Martin
- ORCiD
- Observatoire de Strasbourg, 11, rue de l’Universite , F-67000 Strasbourg, France; Max-Planck-Institut fur Astronomie , Königstuhl 17, D-69117 Heidelberg, Germany
- Alan McConnachie
- ORCiD
- NRC Herzberg Astronomy and Astrophysics , 5071 West Saanich Road, Victoria, BC V9E 2E7, Canada
- Ekta Patel
- ORCiD
- Department of Astronomy, University of California , Berkeley, CA 94720, USA ; [email protected]
- R. Michael Rich
- ORCiD
- Department of Physics and Astronomy, UCLA , 430 Portola Plaza, Box 951547, Los Angeles, CA 90095-1547, USA
- Joshua D. Simon
- ORCiD
- Observatories of the Carnegie Institution for Science , 813 Santa Barbara Street, Pasadena, CA 91101, USA
- Sangmo Tony Sohn
- ORCiD
- Space Telescope Science Institute , 3700 San Martin Drive, Baltimore, MD 21218, USA
- Erik J. Tollerud
- ORCiD
- Space Telescope Science Institute , 3700 San Martin Drive, Baltimore, MD 21218, USA
- Roeland P. van der Marel
- ORCiD
- Space Telescope Science Institute , 3700 San Martin Drive, Baltimore, MD 21218, USA; Center for Astrophysical Sciences, The William H. Miller III Department of Physics & Astronomy, Johns Hopkins University , Baltimore, MD 21218, USA
- DOI
- https://doi.org/10.3847/1538-4357/acf46f
- Journal volume & issue
-
Vol. 956,
no. 2
p. 86
Abstract
We present the lifetime star formation histories (SFHs) for six ultrafaint dwarf (UFD; M _V > − 7.0, $4.9\lt {\mathrm{log}}_{10}({M}_{* }(z=0)/{M}_{\odot })\lt 5.5$ ) satellite galaxies of M31 based on deep color–magnitude diagrams constructed from Hubble Space Telescope imaging. These are the first SFHs obtained from the oldest main-sequence turnoff of UFDs outside the halo of the Milky Way (MW). We find that five UFDs formed at least 50% of their stellar mass by z = 5 (12.6 Gyr ago), similar to known UFDs around the MW, but that 10%–40% of their stellar mass formed at later times. We uncover one remarkable UFD, And xiii , which formed only 10% of its stellar mass by z = 5, and 75% in a rapid burst at z ∼ 2–3, a result that is robust to choices of underlying stellar model and is consistent with its predominantly red horizontal branch. This “young” UFD is the first of its kind and indicates that not all UFDs are necessarily quenched by reionization, which is consistent with predictions from several cosmological simulations of faint dwarf galaxies. SFHs of the combined MW and M31 samples suggest reionization did not homogeneously quench UFDs. We find that the least-massive MW UFDs ( M _* ( z = 5) ≲ 5 × 10 ^4 M _⊙ ) are likely quenched by reionization, whereas more-massive M31 UFDs ( M _* ( z = 5) ≳ 10 ^5 M _⊙ ) may only have their star formation suppressed by reionization and quench at a later time. We discuss these findings in the context of the evolution and quenching of UFDs.
Keywords
