The Proper Motion Field of the Small Magellanic Cloud: Kinematic Evidence for Its Tidal Disruption
van der Marel, Roeland P.
Linden, Sean T.
Fritz, Tobias K.
Kochanek, C. S.
Sohn, Sangmo Tony
Geha, Marla C.
Alcock, Charles R.
AffiliationUniv Arizona, Steward Observ
Keywordsgalaxies: individual (Small Magellanic Cloud)
galaxies: kinematics and dynamics
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PublisherIOP PUBLISHING LTD
CitationPaul Zivick et al 2018 ApJ 864 55
Rights© 2018. The American Astronomical Society. All rights reserved.
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AbstractWe 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 similar to 3 year baseline, using the Hubble Space Telescope (HST) Wide Field Camera 3. Combining this data with our previous five HST fields, and an additional eight measurements from the Gaia-Tycho Astrometric Solution Catalog, brings us to a total of 43 SMC fields. We measure a systemic motion of mu(W) = -0.82 +/- 0.02 (random) +/- 0.10 (systematic) mas yr(-1) and mu(N) = -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.
VersionFinal published version
SponsorsNASA from the STScI [GO-13476, GO-14343]; NASA [NAS 5-26555]; Polish National Science Center [OPUS 2014/15/B/ST9/00093, MAESTRO 2014/14/A/ST9/00121]