The Proper Motion Field of the Small Magellanic Cloud: Kinematic Evidence for Its Tidal Disruption

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 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.NASA 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]This item from the UA Faculty Publications collection is made available by the University of Arizona with support from the University of Arizona Libraries. If you have questions, please contact us at repository@u.library.arizona.edu