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

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

The Astrophysical Journal, Volume 864, Issue 1, article id. 55, 13 pp. (2018).

Fecha de publicación:
9
2018
Número de autores
12
Número de autores del IAC
1
Número de citas
89
Número de citas referidas
78
Descripción
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 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 μ W = ‑0.82 ± 0.02 (random) ± 0.10 (systematic) mas yr‑1 and μ 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.
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