AN ASYMMETRIC STREAMING MOTION IN THE GALACTIC BULGE X-SHAPED STRUCTURE REVEALED BY OGLE-III PROPER MOTIONS

作者：Poleski Radoslaw^*; Udalski Andrzej; Gould Andrew; Szymanski M K; Soszynski I; Kubiak M; Pietrzynski G; Ulaczyk K; Wyrzykowski L

来源：Astrophysical Journal, 2013, 776(2): 76.

DOI：10.1088/0004-637X/776/2/76

• astrometry
• Galaxy: kinematics and dynamics
• Galaxy: structure
• stars: kinematics and dynamics

The Galactic bulge shows a double red clump in sightlines at vertical bar b vertical bar greater than or similar to 5 degrees. and -3 degrees less than or similar to l less than or similar to 4 degrees. This dump is interpreted as the 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 arms 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 degrees, we find that the proper motion difference between the two arms is a linear function of Galactic longitude for -0.degrees 1 %26lt; l %26lt; 0 degrees.5, which we interpret as a streaming motion of the stars within the X-shaped structure. A streaming motion was previously reported based on radial velocity data, not the proper motions. The proper motion difference in longitude is constant for -0 degrees.8 %26lt; l %26lt; -0 degrees.1, which provides an estimate of the bulge rotational speed of 87.9 +/- 8.2 km s(-1) kpc(-1).

• 出版日期2013-10-20