Researchers reveal a wobbly and flared Milky Way disk primarily based on LAMOST-gaia information

Astronomers from National Astronomical Observatories of Chinese Academy of Sciences (NAOC), Shanghai Astronomical Observatory of CAS and Nanjing University have revealed the wobbly and flared nature of the Milky Way disk primarily based on LAMOST-Gaia information, which updates our understanding concerning the galaxy.

The outcomes have been revealed within the Astronomical Journal.

The Milky Way is a typical disk galaxy. In the classical view of the Milky Way, the disk is symmetric and flat on the entire, like a pancake. Stars within the disk rotate across the galactic center, with imply radial and vertical velocities to be zero.

With the assistance of giant observational information supplied by giant survey initiatives in recent times, increasingly particulars hidden within the Milky Way disk have turn out to be obvious, casting doubts on the normal creativeness about our host galaxy.

“The huge number of spectra obtained by LAMOST and the high-precision astrometric data released by Gaia provide a golden opportunity for re-exploring the disk structure,” stated Prof. Zhao Gang, the corresponding creator of the work.

Led by Dr. Ding Pingjie, the primary creator of the work, the researchers chosen ~490,000 Okay-type giants from LAMOST DR8 and Gaia EDR3 as tracers. They discovered that within the spatial vary of Galactocentric radius of 5–15 kpc and three kpc above and beneath the galactic aircraft, vertical wobbles existed within the three-dimensional imply velocities.

Contrary to the classical image that stellar motions preserve symmetric concerning the galactic plane, the Okay-type giants beneath the aircraft are discovered to rotate sooner than these above. Meanwhile, inside disk stars migrate radially towards the outer disk, whereas outer disk stars exhibit alternate inward and outward radial motions, with velocities extremely depending on the vertical distance.

Moreover, a contraction-like respiration mode and an upward bending mode dominate the vertical movement of the outer disk. By comparability, there’s solely a weak rarefaction-like respiration mode and a trivial downward bending mode within the inside disk.

The researchers additional revisited the character of the disk flaring by estimating the scaleheight of the disk with the measured velocity ellipsoid. They discovered that the scaleheight elevated clearly with the growing galactocentric radius, resulting in a flaring function. The outcomes additionally indicated that north and south disks had constant flaring energy. Similar flaring buildings have been additionally detected in some exterior galaxies, which signifies that a flared disk might be a standard phenomenon in disk galaxies.

The wobbly disk probed by the LAMOST-Gaia Okay-type giants might be attributed to the perturbations produced by each inplane substructures (together with the spiral arms and the central bar) and long-lived exterior perturbers (corresponding to a satellite galaxy). The mechanism behind the flaring construction nonetheless stays mysterious.

“This study provides high-quality clues to the galactic structure and evolution. Continuous observations will help to tell a more insightful story of the Milky Way,” stated Xue Xiangxiang, the second creator of the paper.