SiO Maser Survey of the Galactic Disk IRAS Sources. II. | l | ≤ 3o and | b | ≤ 3o, the Galactic Center Area

A survey has been made in the SiO J = 1-0, v = 1 and 2 transitions (~43 GHz) for color-selected IRAS sources in the Galactic-center region of |l| ≤ 3° and |b| ≤ 3° using the Nobeyama 45 m telescope. We have detected 86 of 176 observed sources in the SiO masers. Distances to the sources are deduced from IRAS 12 and 25 μm flux densities and range approximately from 5 to 12 kpc. Radial velocities of the detected sources spread between -300 and 310 km s-1. The longitude-velocity (l-v) diagram exhibits an empty region of sources at l = -04-10 and Vlsr = 20-150 km s-1, which is interpreted as an undersampling effect of sources in the IRAS catalog at the Galactic central disk. The rotation rate, velocity dispersion, tilt angle of the rotation axis, and velocity shift at l = 0° are derived by fitting the velocities of the sources with a straight line as a function of Galactic longitude. These quantities are compatible with those obtained from previous observations of bulge stars with |b| > 3°. The average radial velocity of subsamples of stars tends to increase with distance, suggesting the presence streaming motion of stars in a barlike bulge. We conclude that most of the IRAS sources in the sample belong to the bulge.