Astronomy and Astrophysics – Astrophysics – Galaxy Astrophysics
Scientific paper
2010-08-25
Astronomy Letters, 2010 Vol. 36, No. 9, pp. 634-644
Astronomy and Astrophysics
Astrophysics
Galaxy Astrophysics
17 pages, 3 tables, 2 figures
Scientific paper
10.1134/S1063773710090021
We analyze the three-dimensional kinematics of about 82000 Tycho-2 stars belonging to the red giant clump (RGC). First, based on all of the currently available data, we have determined new, most probable components of the residual rotation vector of the optical realization of the ICRS/HIPPARCOS system relative to an inertial frame of reference, \omega_x,\omega_y,\omega_z)= (-0.11,0.24,-0.52)+/-(0.14,0.10,0.16) mas/yr. The stellar proper motions in RA have then be corrected by applying the correction \omega_z = -0.52 mas/yr. We show that, apart from their involvement in the general Galactic rotation described by the Oort constants A= 15.82+/-0.21 km/s/kpc and B=-10.87+/-0.15 km/s/kpc, the RGC stars have kinematic peculiarities in the Galactic yz plane related to the kinematics of the warped stellar-gaseous Galactic disk. We show that the parameters of the linear Ogorodnikov-Milne model that describe the kinematics of RGC stars in the zx plane do not differ significantly from zero. The situation in the yz plane is different. For example, the component of the solid-body rotation vector of the local solar neighborhood around the Galactic x axis is M_32- = -2.6+/-0.2 km/s/kpc. Two parameters of the deformation tensor in this plane, namely M_23^+ = 1.0+/-0.2 km/s/kpc and (M_33-M_22)= -1.3+/-0.4 km/s/kpc, also differ significantly from zero. On the whole, the kinematics of the warped stellar-gaseous Galactic disk in the local solar neighborhood can be described as a rotation around the Galactic X axis (close to the line of nodes of this structure) with an angular velocity (-3.1+/-0.5) < \Omega_W < (-4.4+/-0.5) km/s/kpc.
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