The kinematics and zero-point of the log P–〈MK〉 relation for Galactic RR Lyrae variables via statistical parallax |
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| Authors: | A K Dambis |
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| Institution: | Sternberg Astronomical Institute, Universitetskii pr. 13, Moscow, 119992, Russia |
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| Abstract: | We use accurate absolute proper motions and Two-Micron All-Sky Survey Ks -band apparent magnitudes for 364 Galactic RR Lyrae variables to determine the kinematical parameters of the Galactic RR Lyrae population and constrain the zero-point of the Ks -band period–luminosity relation for these stars via statistical parallax. We find the mean velocities of the halo- and thick-disc RR Lyrae populations in the solar neighbourhood to be U 0(Halo), V 0(Halo), W 0(Halo)]= (?12 ± 10, ?217 ± 9, ?6 ± 6) km s?1 and U 0(Disc), V 0(Disc), W 0(Disc)]= (?15 ± 7, ?44 ± 7, ?25 ± 5) km s?1 , respectively, and the corresponding components of the velocity-dispersion ellipsoids, σ VR (Halo), σ V θ(Halo), σ W (Halo)]= (167 ± 9, 86 ± 6, 78 ± 5) km s?1 and σ VR (Disc), σ V θ(Disc), σ W (Disc)]= (55 ± 7, 44 ± 6, 30 ± 4) km s?1 , respectively. The fraction of thick-disc stars is estimated at 0.25 ± 0.03 . The corrected infrared period–luminosity relation is  , implying a Large Magellanic Cloud (LMC) distance modulus of 18.27 ± 0.08 and a solar Galactocentric distance of 7.58 ± 0.40 kpc . Our results suggest no or slightly prograde rotation for the population of halo RR Lyraes in the Milky Way. |
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| Keywords: | stars: distances stars: horizontal branch stars: kinematics stars: variables: other Galaxy: kinematics and dynamics distance scale |
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