Proper Motions and Orbits of Distant Local Group Dwarf Galaxies from a Combination of Gaia and Hubble Data

Paul Bennet; Ekta Patel; Sangmo Tony Sohn; Andrés del Pino Molina; Roeland P. van der Marel; Mattia Libralato; Laura L. Watkins; Antonio Aparicio; Gurtina Besla; Carme Gallart; Mark A. Fardal; Matteo Monelli; Elena Sacchi; Erik Tollerud; Daniel R. Weisz

doi:10.3847/1538-4357/ad5349

The Astrophysical Journal (Jan 2024)

Proper Motions and Orbits of Distant Local Group Dwarf Galaxies from a Combination of Gaia and Hubble Data

Paul Bennet,
Ekta Patel,
Sangmo Tony Sohn,
Andrés del Pino Molina,
Roeland P. van der Marel,
Mattia Libralato,
Laura L. Watkins,
Antonio Aparicio,
Gurtina Besla,
Carme Gallart,
Mark A. Fardal,
Matteo Monelli,
Elena Sacchi,
Erik Tollerud,
Daniel R. Weisz

Affiliations

Paul Bennet: ORCiD; Space Telescope Science Institute , 3700 San Martin Drive, Baltimore, MD 21218, USA ; [email protected]
Ekta Patel: ORCiD; Department of Astronomy, University of California , Berkeley, 501 Campbell Hall, Berkeley, CA, 94720, USA; Department of Physics and Astronomy, University of Utah , 115 South 1400 East, Salt Lake City, Utah 84112, USA
Sangmo Tony Sohn: ORCiD; Space Telescope Science Institute , 3700 San Martin Drive, Baltimore, MD 21218, USA ; [email protected]
Andrés del Pino Molina: ORCiD; Centro de Estudios de Física del Cosmos de Aragón (CEFCA) , Unidad Asociada al CSIC, Plaza San Juan 1, 44001, Teruel, Spain
Roeland P. van der Marel: ORCiD; Space Telescope Science Institute , 3700 San Martin Drive, Baltimore, MD 21218, USA ; [email protected]; Center for Astrophysical Sciences, The William H. Miller III Department of Physics & Astronomy, Johns Hopkins University , Baltimore, MD 21218, USA
Mattia Libralato: ORCiD; AURA for the European Space Agency (ESA) , ESA Office, Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218, USA
Laura L. Watkins: ORCiD; AURA for the European Space Agency (ESA) , ESA Office, Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218, USA
Antonio Aparicio: ORCiD; Intituto de Astrofísica de Canarias , 3200, La Laguna, Tenerife, Canary Islands, Spain; Departamento de Astrofísica, Universidad de La Laguna , 3200, La Laguna, Tenerife, Canary Islands, Spain
Gurtina Besla: ORCiD; Steward Observatory, University of Arizona , 933 North Cherry Avenue, Tucson, AZ 85721, USA
Carme Gallart: ORCiD; Intituto de Astrofísica de Canarias , 3200, La Laguna, Tenerife, Canary Islands, Spain; Departamento de Astrofísica, Universidad de La Laguna , 3200, La Laguna, Tenerife, Canary Islands, Spain
Mark A. Fardal: ORCiD; Eureka Scientific , 2452 Delmer Street, Suite 100, Oakland, CA 94602, USA
Matteo Monelli: ORCiD; Intituto de Astrofísica de Canarias , 3200, La Laguna, Tenerife, Canary Islands, Spain; Departamento de Astrofísica, Universidad de La Laguna , 3200, La Laguna, Tenerife, Canary Islands, Spain; INAF-Osservatorio Astronomico di Roma , via Frascati 33, 00040 Monte Porzio Catone, Italy
Elena Sacchi: ORCiD; Leibniz-Institut für Astrophysik Potsdam , An der Sternwarte 16, 14482 Potsdam, Germany
Erik Tollerud: ORCiD; Space Telescope Science Institute , 3700 San Martin Drive, Baltimore, MD 21218, USA ; [email protected]
Daniel R. Weisz: ORCiD; Department of Astronomy, University of California , Berkeley, 501 Campbell Hall, Berkeley, CA, 94720, USA

DOI: https://doi.org/10.3847/1538-4357/ad5349
Journal volume & issue: Vol. 971, no. 1
p. 98

Abstract

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We have determined the proper motions (PMs) of 12 dwarf galaxies in the Local Group (LG), ranging from the outer Milky Way (MW) halo to the edge of the LG. We used the Hubble Space Telescope (HST) as the first and Gaia as the second epoch using the GaiaHub software. For Leo A and Sag DIG, we also used multi-epoch HST measurements relative to background galaxies. Orbital histories derived using these PMs show that two-thirds of the galaxies in our sample are on first infall with >90% certainty. The observed star formation histories of these first-infall dwarfs are generally consistent with infalling dwarfs in simulations. The remaining four galaxies have crossed the virial radius of either the MW or M31. When we compare their star formation (SF) and orbital histories we find tentative agreement between the inferred pattern of SF with the timing of dynamical events in the orbital histories. For Leo I, SF activity rises as the dwarf crosses the MW’s virial radius, culminating in a burst of SF shortly before pericenter (≈1.7 Gyr ago). The SF then declines after pericenter, but with some smaller bursts before its recent quenching (≈0.3 Gyr ago). This shows that even small dwarfs like Leo I can hold onto gas reservoirs and avoid quenching for several gigayears after falling into their host, which is longer than generally found in simulations. Leo II, NGC 6822, and IC 10 are also qualitatively consistent with this SF pattern in relation to their orbit, but more tentatively due to larger uncertainties.

Published in The Astrophysical Journal

ISSN: 1538-4357 (Online)
Publisher: IOP Publishing
Country of publisher: United Kingdom
LCC subjects: Science: Astronomy: Astrophysics
Website: https://iopscience.iop.org/journal/0004-637X

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