The nearby spiral density-wave structure of the Galaxy

Abstract

Accurate measurements of distances and line-of-sight velocities of 19291 intermediate-old giant stars in the near-infrared with typical uncertainties in the distances and velocities of 5 per cent and 0.1 km s^-1 have recently been carried out to examine the Galactic disc with the APOGEE survey. In the framework of the Lin-Shu density-wave proposal for the galactic spiral structure, we use the APOGEE-RC DR13 data to investigate coherent non-axisymmetric flows within a few kiloparsecs from the Sun which are superimposed on a circular motion in the disc. Systematic wave-like departures of velocities from circular motion for stars are really detected. These systematic non-circular velocities are used to recover the parameters of the spiral arm segments of density waves of the Galaxy in the solar vicinity. The results of the work can be tested with the large amount of data from the Gaia satellite mission in the near future.