Near-infrared observations of the IRAS/SiO sources in the Galactic bulge: A large scale distribution

Abstract

Near-infrared photometric obserwttions in the J-, H-, and K-bands were made for 120 IRAS sources toward the Galactic bulge (-10° < l < 15° and |b| < 3°, excluding |l| < 3°). They are well-confirmed, mass-losing late-type stars having accurate radial velocities derived from SiO maser observations. For 118 sources, single, unambiguous near-infrared counterparts were found within the errors of the IRAS/MSX positions; and for the other 2 sources, faint candidates only detectable in the K-band were found. From the J-, H-, K-band and IRAS 12 and 25 μm intensities, we estimated the spectral energy distributions of the sources, and obtained distances assuming a constant intrinsic luminosity. Adding all of the distance data of the IRAS/SiO sources in -10° < l < 25° published in previous papers, we mapped the positions of 272 sampled stars onto the Galactic plane. The map clearly shows a bar structure, where the major axis of the bar is oriented 22°(±8°) from the Sun-Galactic center line. We also reanalyzed the radial-velocity shift with the distance in this sample. These analyses suggest that the data are consistent with the current bar theory of the Galactic bulge.