http://arxiv.org/abs/1910.00632
We have studied the kinematic properties of the candidates for hot subdwarfs (HSDs) selected by Geier et al. from the Gaia DR2 catalogue. We have used a total of 12 515 stars with relative trigonometric parallax errors less than 30\%. The HSDs are shown to have different kinematics, depending on their positions on the celestial sphere. For example, the sample of low-latitude $(|b|<20^\circ)$ HSDs rotates around the Galactic center with a linear velocity $V_0=221\pm5$ km s$^{-1}$. This suggests that they belong to the Galactic thin disk. At the same time, they lag behind the local standard of rest by $\Delta V_\odot\sim16$ km s$^{-1}$ due to the asymmetric drift. The high-latitude ($|b|\geq20^\circ$) HSDs rotate with a considerably lower velocity, $V_0=168\pm6$ km s$^{-1}$. Their lagging behind the local standard of rest is already $\Delta V_\odot\sim40$ km s$^{-1}$. Based on the entire sample of 12 515 HSDs, we have found a positive rotation around the $x$ axis significantly differing from zero with an angular velocity $\omega_1=1.36\pm0.24$ km s$^{-1}$ kpc$^{-1}$. We have studied the samples of HSDs that are complete within $r<1.5$ kpc. Based on them, we have traced the evolution of the parameters of the residual velocity ellipsoid as a function of both latitude $|b|$ and coordinate $|z|.$ The following vertical disk scale heights have been found: $h=180\pm6$ and $290\pm10$ pc from the low- and high-latitude HSDs, respectively. A new estimate of the local stellar density $\Sigma_{out}=53\pm4~M_{\odot}$/kpc$^2$ kpc$^{-2}$ has been obtained for $z_{out}=0.56$ kpc from the high-latitude HSDs.
V. Bobylev and A. Bajkova
Thu, 3 Oct 19
6/59
Comments: 18 pages, 4 figures, 4 tables