Abstract
We have studied the kinematic properties of the candidates for hot subdwarfs (HSDs) selected by Geier et al. from theGaiaDR2 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°) HSDs rotates around the Galactic center with a linear velocity V0 = 221 ± 5 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 ΔV☉ ~ 16 km s−1 due to the asymmetric drift. The high-latitude (|b| ≥ 20°) HSDs rotate with a considerably lower velocity, V☉ = 168 ± 6 km s−1. Their lagging behind the local standard of rest is already ΔV☉ ∼ 40 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 ω1 = 1.36±0.24 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 ± 6 and 290 ± 10 pc from the low- and high-latitude HSDs, respectively. A new estimate of the local stellar density Σout = 53 ± 4 M☉ kpc−2 has been obtained for zout = 0.56 kpc from the high-latitude HSDs.
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Russian Text © The Author(s), 2019, published in Pis’ma v Astronomicheskii Zhurnal, 2019, Vol. 45, No. 9, pp. 622–635.
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Bobylev, V.V., Bajkova, A.T. Kinematics of Hot Subdwarfs from the Gaia DR2 Catalogue. Astron. Lett. 45, 580–592 (2019). https://doi.org/10.1134/S1063773719080012
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DOI: https://doi.org/10.1134/S1063773719080012