Kinematics of Red Variables in the Solar Neighborhood I. Basic Data Obtained by an SiO Maser Survey

TL;DR

This study surveys 379 red variable stars in the Solar neighborhood using SiO maser lines to analyze their velocities and motions, revealing new stellar groups with noncircular Galactic motions related to spiral arms.

Contribution

First comprehensive SiO maser survey of red variables in the Solar neighborhood, identifying new stellar groups with anomalous motions linked to spiral arms.

Findings

Identified three groups of stars with noncircular motions.

Discovered two new deviant groups toward Perseus and Sagittarius arms.

Observed motions consistent with VLBI measurements of spiral arm dynamics.

Abstract

In order to study the streaming motions of miras in the Solar neighborhood, we newly surveyed 379 red variables in the SiO maser lines at 42.821 and 43.122 GHz with the Nobeyama 45m radio telescope. Accurate radial velocities were obtained for 229 (220 new) detected stars. The sample is selected from optical variables found by new automated surveys: the Northern Sky Variability Survey and the All Sky Automated Survey. The new sample consists of the "bluer" objects compared with those observed in the previous SiO surveys. The distances to the objects are estimated using the period-luminosity relation, and they are mostly less than 3 kpc from the Sun. The longitude-velocity diagram reveals three prominent groups of stars deviant from the circular Galactic rotation with a flat rotation curve. In addition to the Hercules group of stars which was studied before, we found two new deviant groups: one toward the Perseus arm and the other toward the Sagittarius arm. These two groups both exhibit anomalous motions toward the Galactic center, which seem to be consistent with the noncircular motions of these spiral arms found in the recent VLBI proper-motion measurements for maser gas clumps.