Kinematics of B-F Stars as a Function of Their Dereddened Color from Gaia and PCRV Data

Abstract

Parallaxes with an accuracy better than 10% and proper motions from the Gaia DR1 TGAS catalogue, radial velocities from the PCRV, Tycho-2 photometry, PARSEC, MIST, YaPSI, BaSTI isochrones, and the most accurate reddening and extinction estimates have been used to analyze the kinematics of 9543 thin-disk B-F stars as a function of their dereddened color. These stars are located on the Hertzsprung-Russell diagram relative to the isochrones with a high accuracy. This has allowed me to conclude that the reddening and extinction were significantly underestimated in some kinematic studies of other authors. The median accuracy of the velocity components U, V, W in this study is 1.7 km/s, although outside the range $-0.1<(B_T-V_T)_0<0.5$ the kinematic characteristics are noticeably biased due to the incompleteness of the sample. We have confirmed the variations in the mean velocity of stars relative to the Sun and the stellar velocity dispersion as a function of their dereddened color known from the Hipparcos data. Given the age estimates for the stars under consideration from the TRILEGAL model and the Geneva-Copenhagen survey, these variations may be considered as variations as a function of the age. A comparison of our results with the results of other studies of the stellar kinematics near the Sun has shown that selection and reddening underestimation explain almost completely the discrepancies between the results. The dispersions and mean velocities from the results of reliable studies fit into a $\pm2$ km/s corridor, while the ratios $\sigma_V/\sigma_U$ and $\sigma_W/\sigma_U$ fit into $\pm0.05$. Based on all reliable studies in the range $-0.1<(B_T-V_T)_0<0.5$, i.e., for an age from 0.23 to 2.4 Gyr, we have found that the stellar velocity dispersions in km/s are proportional to the age in Gyr raised to the power $\beta_U=0.33$, $\beta_V=0.285$, and $\beta_W=0.37$.