The Galaxy Kinematics from OB Stars with Proper Motions from the Gaia DR1 Catalog

TL;DR

This study uses Gaia DR1 proper motions and parallaxes of OB stars to refine Galactic rotation parameters, compare distance scales, and improve understanding of Galactic kinematics.

Contribution

It provides new Galactic rotation parameters using Gaia DR1 data and compares different distance scales for OB stars, refining the Galactic kinematic model.

Findings

Proper motions from Gaia DR1 reduce errors in Galactic rotation parameters.

The Gaia DR1 distance scale is close to the standard scale, approximately 0.96.

Derived Galactic kinematic parameters include Oort constants and solar motion components.

Abstract

We consider two previously studied samples of OB stars with different distance scales. The first one consists of 98 massive spectroscopic binary stars with photometric distances, and the second one consists on 140 OB stars with the distances determined along the lines of interstellar calcium. The OB stars are located at distances up to 7 kpc from the Sun. They are identified with the Gaia DR1 catalog. It is shown that the use of the proper motions, taken from the Gaia DR1 catalog, allows to reduce random errors of determination of the Galactic rotation parameters in comparison with the previously known ones. From the analysis of 208 OB stars from the Gaia DR1 catalog with proper motions and parallaxes with relative errors less than 200% we found the Galactic kinematic parameters. In addition the Galactic rotation parameters were obtained from only line-of-sight velocities of the same stars. From the comparison of the two values of \Omega^{'}_0 a distance scale of the Gaia DR1 catalog was determined as a value close to unit, namely 0.96. From 238 OB-stars of the united sample with photometric distances for stars of the first sample and distances in the calcium scale for stars of the second sample, line-of-sight velocities and proper motions from the Gaia DR1 catalog, were found the following kinematic parameters: (U,V,W)_\odot=(8.19,9.28,8.79)+/-(0.74,0.92,0.74) km/s, \Omega_0=31.53+/-0.54 km/s/kpc, \Omega^{'}_0=-4.44+/-0.12 km/s/kpc^2, \Omega^{"}_0=0.706+/-0.100 km/s/kpc^3, here Oort constants: A=-17.77+/-0.46 km/s/kpc, B=13.76+/-0.71 km/s/kpc and V_0=252+/-8 km/s.