We find that Galactic disk stars near the anticenter exhibit velocity asymmetries in both the Galactocentric radial and vertical components across the mid-plane as well as azimuthally. These findings are based on LAMOST spectroscopic velocities for a sample of ~400,000 F-type stars, combined with proper motions from the PPMXL catalog for which we have derived corrections to the zero points based in part on spectroscopically discovered galaxies and QSOs from LAMOST. In the region within 2 kpc outside the Sun's radius and +/-2 kpc from the Galactic midplane, we show that stars above the plane exhibit net outward radial motions with downward vertical velocities, while stars below the plane have roughly the opposite behavior. We discuss this in the context of other recent findings, and conclude that we are likely seeing the signature of vertical disturbances to the disk due to an external perturbation.
@article{arxiv.1309.6314,
title = {Substructure in bulk velocities of Milky Way disk stars},
author = {Jeffrey L. Carlin and James DeLaunay and Heidi Jo Newberg and Licai Deng and Daniel Gole and Kathleen Grabowski and Ge Jin and Chao Liu and Xiaowei Liu and A-Li Luo and Haibo Yuan and Haotong Zhang and Gang Zhao and Yongheng Zhao},
journal= {arXiv preprint arXiv:1309.6314},
year = {2015}
}
Comments
12 pages, 3 figures, 2 tables; accepted to ApJ Letters