Kinematical and ellipsoidal properties of the inner-halo hot subdwarfs observed in Gaia DR3 and LAMOST DR7

Abstract

Here, we report the kinematical parameters of inner-halo hot subdwarfs located within $\left(d\le 15\text{kpc}\right)$ at high Galactic latitudes $\left(b^o\ge 20\right)$. The study included three program stars for one of the extreme He-rich groups (eHe-1) with eccentricity (e= 0.65) and the z-component of the angular momentum (J_z = 4288.66 kpc km s⁻¹), the inner halo program I with 121 points $\left(T_{\text{eff}}\ge 24,000\right)$ and their subsections, i.e. inner halo program II (sdB; 79 points) with $\left(40,000\ge T_{\text{eff}}\ge 24,000\right)$ and inner halo program III (sdO; 42 points) with $\left(80,000\ge T_{\text{eff}}\ge 40,000\right)$. First, we calculated the spatial velocities ($\overline{U},\overline{V},\overline{W};\text{km}{s}^{-1})$ along the Galactic coordinates (i.e., 25.73 ± ± 5.07, 28.79 ± 5.37, −14.51 ± 3.81) and their dispersion velocities $\left({\sigma }_1,{\sigma }_2,{\sigma }_3;\text{km}{s}^{-1}\right)$ = (161.94 ± 12.73, 140.31 ± 11.85, 101.57 ± 10.08) and subsequently their subsections sdB and sdO. Second, we calculated the vertex longitudes $\left(l_2\right)$ and the Solar motion $\left(S_{\odot }=41.246.42\text{km}{s}^{-1}\right)$ as well as their subsections. Finally, based on the kinematic relation of the ratio $\left({\sigma }_2/{\sigma }_1\right)$ and our previously computed numerical value of the angular rotation rate $\left(\left|A-B\right|=26.07\pm 5.10;\text{km}{s}^{-1}\text{kp}{c}^{-1}\right)$, we obtained the average Oort's constants as $\left(A\&B;\text{km}{s}^{-1}\text{kp}{c}^{-1}\right)$ = (9.38 ± 0.33, −16.69 ± 0.25).