Paper detail

Detection of periodic variations in vertical velocities of Galactic masers

We have collected literature data on Galactic masers with trigonometric parallaxes measured by means of 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 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_0 in the spiral density wave is -79^\circ+/-14^\circ and -199^\circ+/-16^\circ from the residual tangential and radial velocities, respectively. The most interesting result of this work is detecting a wave in vertical spatial velocities W versus distance R from the Galactic rotation axis. From the spectral analysis, we have found the following characteristics of this wave: the perturbation wavelength is λ_W=3.4+/-0.7 kpc and the amplitude f_W=4.3+/-1.2 km/s.