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arXiv · 1710.02462

Proper Motion of the Sextans Dwarf Galaxy from Subaru Suprime-Cam Data

Dana I. Casetti-Dinescu·Terrence M. Girard·Michael Schriefer
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Abstract

We have measured the absolute proper motion of the Sextans dwarf spheroidal galaxy using Subaru Suprime-Cam images taken at three epochs, with a time baseline of ~ 10 years. We astrometrically calibrate each epoch by constructing distortion-correction maps from the best available Subaru Suprime-Cam dithered data sets and from Gaia DR1 positions. The magnitude limit of the proper-motion study is V ~ 24. The area covered is 26.7 x 23.3 arcmin, which is still within the core radius of Sextans. The derived proper motion is (mu_a, mu_d) = (-0.409 +/- 0.050, -0.047 +/- 0.058) mas/yr. The direction of motion is perpendicular to the major axis of the galaxy. Our measurement, combined with radial velocity and distance from the literature, implies a low eccentricity orbit, with a moderate inclination to the Galactic plane, and a period of 3 Gyr. Sextans is now some 0.4 Gyr away from its pericenter ( r_peri ~ 75 kpc), moving toward its apocenter (r_apo ~ 132 kpc). Its orbit is inconsistent with membership to the vast polar structure of Galactic satellites.

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Dana I. Casetti-Dinescu, Terrence M. Girard, Michael Schriefer. 2017-10-06. Proper Motion of the Sextans Dwarf Galaxy from Subaru Suprime-Cam Data. https://doi.org/10.1093/mnras%2Fstx2645

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