The proper motion field of the small magellanic cloud: Kinematic evidence for its tidal disruption

Paul Zivick, Nitya Kallivayalil, Roeland P. van der Marel, Gurtina Besla, Sean T. Linden, Szymon Kozlowski, Tobias K. Fritz, C. S. Kochanek, J. Anderson, Sangmo Tony Sohn, Marla C. Geha, Charles R. Alcock

Research output: Contribution to journalArticlepeer-review

Abstract

We present a new measurement of the systemic proper motion of the Small Magellanic Cloud (SMC), based on an expanded set of 30 fields containing background quasars and spanning a ∼3 year baseline, using the Hubble Space Telescope (HST) Wide Field Camera 3. Combining this data with our previous 5 HST fields, and an additional 8 measurements from the Gaia-Tycho Astrometric Solution Catalog, brings us to a total of 43 SMC fields. We measure a systemic motion of μW =-0.82 ± 0.02 (random) ± 0.10 (systematic) mas yr-1and μN =-1.21 ± 0.01 (random) ± 0.03 (systematic) mas yr-1. After subtraction of the systemic motion, we find little evidence for rotation, but find an ordered mean motion radially away from the SMC in the outer regions of the galaxy, indicating that the SMC is in the process of tidal disruption. We model the past interactions of the Clouds with each other based on the measured present-day relative velocity between them of 103 ± 26 km s-1. We find that in 97% of our considered cases, the Clouds experienced a direct collision 147 ± 33 Myr ago, with a mean impact parameter of 7.5 ± 2.5 kpc.

Original languageEnglish (US)
JournalUnknown Journal
StatePublished - Apr 11 2018

Keywords

  • Galaxies: Kinematics and Dynamics
  • Galaxies: Magellanic Clouds

ASJC Scopus subject areas

  • General

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