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Signatures of Tidal Disruption in Ultra-Faint Dwarf Galaxies: A Combined HST, Gaia, and MMT/Hectochelle Study of Leo V

Mutlu-Pakdil, Burçin, Sand, David J., Walker, Matthew G., Caldwell, Nelson, Carlin, Jeffrey L., Collins, Michelle L., Crnojević, Denija, Mateo, Mario, Olszewski, Edward W., Seth, Anil C. , Strader, Jay, Willman, Beth and Zaritsky, Dennis (2019) Signatures of Tidal Disruption in Ultra-Faint Dwarf Galaxies: A Combined HST, Gaia, and MMT/Hectochelle Study of Leo V The Astrophysical Journal.

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The ultra-faint dwarf galaxy Leo V has shown both photometric overdensities and kinematic members at large radii, along with a tentative kinematic gradient, suggesting that it may have undergone a close encounter with the Milky Way. We investigate these signs of disruption through a combination of i) high-precision photometry obtained with the Hubble Space Telescope (HST), ii) two epochs of stellar spectra obtained with the Hectochelle Spectrograph on the MMT, and iii) measurements from the Gaia mission. Using the HST data, we examine one of the reported stream-like overdensities at large radii, and conclude that it is not a true stellar stream, but instead a clump of foreground stars and background galaxies. Our spectroscopic analysis shows that one known member star is likely a binary, and challenges the membership status of three others, including two distant candidates that had formerly provided evidence for overall stellar mass loss. We also find evidence that the proposed kinematic gradient across Leo V might be due to small number statistics. We update the systemic proper motion of Leo V, finding (μαcosδ,μδ)=(0.009±0.560, −0.777±0.314) mas yr−1, which is consistent with its reported orbit that did not put Leo V at risk of being disturbed by the Milky Way. These findings remove most of the observational clues that suggested Leo V was disrupting, however, we also find new plausible member stars, two of which are located ˃5 half-light radii from the main body. These stars require further investigation. Therefore, the nature of Leo V still remains an open question.

Item Type: Article
Divisions : Faculty of Engineering and Physical Sciences > Physics
Authors :
Mutlu-Pakdil, Burçin
Sand, David J.
Walker, Matthew G.
Caldwell, Nelson
Carlin, Jeffrey L.
Collins, Michelle
Crnojević, Denija
Mateo, Mario
Olszewski, Edward W.
Seth, Anil C.
Strader, Jay
Willman, Beth
Zaritsky, Dennis
Date : 2019
Copyright Disclaimer : © 2019. The American Astronomical Society. All rights reserved.
Related URLs :
Depositing User : Clive Harris
Date Deposited : 01 Oct 2019 10:54
Last Modified : 01 Oct 2019 10:54

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