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arXiv · 1304.6084

Asymmetric streaming motion in the Galactic bulge X-shaped structure revealed by the OGLE-III proper motions

R. Poleski·A. Udalski·A. Gould·M. K. Szymanski·I. Soszynski·M. Kubiak·G. Pietrzynski·K. Ulaczyk·L. Wyrzykowski
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Abstract

The Galactic bulge shows a double red clump in sight lines with |b| > 5 deg and -3 deg < l < 4 deg. It is interpreted as a signature of an X-shaped structure seen almost edge-on. We measure the proper motions of the stars belonging to the closer and the further arm of the X-shaped structure. The intrinsic kinematic properties of the two arms are found by incorporating information taken from the luminosity function. At b = -5 deg we find that the proper motion difference between the two arms is a linear function of the Galactic longitude for -0.1 deg < l < 0.5 deg, which we interpret as a streaming motion of the stars within the X-shaped structure. Such a streaming motion has not previously been reported. The proper motion difference is constant for -0.8 deg < l < -0.1 deg, which gives us an estimate of bulge rotation speed of 87.9 +/- 8.2 km/s/kpc.

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R. Poleski, A. Udalski, A. Gould, M. K. Szymanski, I. Soszynski, M. Kubiak, G. Pietrzynski, K. Ulaczyk, L. Wyrzykowski. 2013-04-22. Asymmetric streaming motion in the Galactic bulge X-shaped structure revealed by the OGLE-III proper motions. https://doi.org/10.1088/0004-637x/776/2/76

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