Galactic masers: kinematics, spiral structure and the disk dynamic state

A. S. Rastorguev; N. D. Utkin; M. V. Zabolotskikh; A. K. Dambis; A. T. Bajkova; V. V. Bobylev

doi:10.1134/S1990341317020043

paper

Galactic masers: kinematics, spiral structure and the disk dynamic state

arXiv:1603.09124 · doi:10.1134/S1990341317020043

Abstract

We applied the currently most comprehensive version of the statistical-parallax technique to derive kinematical parameters of the maser sample with 136 sources. Our kinematic model comprises the overall rotation of the Galactic disk and the spiral density-wave effects. We take into account the variation of radial velocity dispersion with Galactocentric distance. The best description of the velocity field is provided by the model with constant radial and vertical velocity dispersions, $(σ U 0, σ W 0) \approx (9.4 \pm 0.9, 5.9 \pm 0.8) k m / s$ . We compute flat Galactic rotation curve over the Galactocentric distance interval from 3 to 15 kpc and find the local circular rotation velocity to be $V_{0} \approx (235 - 238)$ ~ km/s $\pm 7$ ~ km/s. We also determine the parameters of the four-armed spiral pattern (pitch angle $i \approx (- 10.4 \pm 0.3)^{\circ}$ and the phase of the Sun $χ_{0} \approx (125 \pm 10)^{\circ}$ ). The radial and tangential spiral perturbations are about $f_{R} \approx (- 6.9 \pm 1.4)$ ~km/s, $f_{Θ} \approx (+ 2.8 \pm 1.0$ ) ~km/s. The kinematic data yield a solar Galactocentric distance of $R_{0} \approx (8.24 \pm 0.12) k p c$ . Based on rotation curve parameters and the asymmetric drift we Infer the exponential disk scale $H_{D} \approx (2.7 \pm 0.2)$ ~kpc under assumption of marginal stability of the intermediate-age disk, and finally we estimate the minimum local surface disk density, $Σ (R_{0}) > (26 \pm 3) M_{⊙} p c^{- 2}$ .

arXiv comment16 pages, 8 figures, 5 tables

Galactic masers: kinematics, spiral structure and the disk dynamic state

Abstract

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