2015MNRAS.447L..50B

We have collected literature data on Galactic masers with trigonometric parallaxes measured by means of very-long-baseline interferometry (VLBI). We have obtained series of residual tangential (ΔV_circ) and radial (ΔV_R) velocities for 107 masers. Based on these series, we have re-determined the parameters of the Galactic spiral density wave using the method of spectral (periodogram) analysis. The tangential and radial perturbation amplitudes are f_θ = 6.0 ± 2.6 km/s and f_R = 7.2 ± 2.2 km/s, respectively; the perturbation wavelengths are λ_θ = 3.2 ± 0.5 kpc and λ_R = 3.0 ± 0.6 kpc for a four-armed spiral model, m = 4. The phase of the Sun, χ_☉, in the spiral density wave is -79° ± 14° and -199° ± 16° from the residual tangential and radial velocities, respectively. The most interesting result of this work is detecting a wave in vertical spatial velocity (W) versus distance R from the Galactic rotation axis. From spectral analysis, we have found the following characteristics for this wave: perturbation wavelength λ_W = 3.4 ± 0.7 kpc and amplitude f_W = 4.3 ± 1.2 km/s.