Dr. Ya-Qian Wu from National Astronomical Observatories of Chinese Academy of Sciences (NAOC) investigated the stellar kinematics of the Galactic disc in 7<R<13 kpc by using a sample of 118945 red giant branch (RGB) stars from the Large Sky Area Multi-Object Fiber Spectroscopic Telescope (LAMOST) and Gaia. This work reveals abundant but clear stellar kinematic patterns and structures in the age-metallicity and the R-Z planes.

This research result has been published online in the Monthly Notices of the Royal Astronomical Society.

An interesting issue of contemporary astrophysics is our understanding of the formation and evolution of the Galactic disc. Modern large-scale sky surveys, such as the Gaia astrometry survey and a number of Galactic spectroscopic surveys, such as the RAVE, the SDSS, the LAMOST, the GALAH and APOGEE, have revealed unprecedented details and phenomena of our Milky Way disc through the study of the stellar distributions, chemistry and kinematics of millions of stars.

“We all know that the Milky Way is composed of two major components, the thin disc and the thick disc,” said Dr. Ya-Qian Wu, who is the lead author of this study.

“In this work, we present kinematics properties using actions and skewness of the distributions which have not been much explored.”

“Especially, the skewness of Vφ and Jφ reveals a new substructure at R~ 12 kpc and Z ~ 0 kpc, possibly related to dynamical effects of spiral arms in the outer disc. It deserves further study,” said Dr. Maosheng Xiang, who is the key co-authors of this study.

“This work is based on her latest work which included 0.64 million LAMOST RGB stars with accurate age and mass estimates,” said Prof. Yuqin Chen.

“This work helps us understand the radial migration process in the Galactic disk based on the largest sample of stars, and it shows the advantage of the LAMOST survey.”

Dr. Maosheng Xiang from Max-Planck Institute for Astronomy and Prof. Yuqin Chen at NAOC have contributed to this work as key co-authors. This work was supported by Joint Research Fund in Astronomy, NSFC and Chinese Academy of Sciences.

Fig.1: Distributions of the LAMOST RGB stars in the Galactic R–Z plane. (Credit: Ya-Qian Wu)

This paper can be accessed at https://academic.oup.com/mnras/article/501/4/4917/6104314