SiO Maser Survey of the Inner Bar of the Galactic Bulge

We surveyed 291 MSX/2MASS infrared objects in the 7 x 2 deg area of thegalactic center in the 43 GHz SiO J=1--0 v=1 and 2 maser lines, obtainingaccurate radial velocities of 163 detected objects. The surveyed area is theregion where the IRAS catalog is incomplete due to contamination by high sourcedensity. The objects in the present MSX/2MASS sample were chosen to havesimilar infrared characteristics to those of the previous SiO-maser-surveysamples based on the color selected IRAS sources. The sampling based on the2MASS catalog causes a bias to the foreside objects of the bulge due to heavyobscuration by interstellar dust; the detections are considerably leaned on theV_{lsr}<0 side. The l--v diagram reveals two conspicuous features, which werenot present or tenuous in the previous studies: one feature indicating a linearvelocity increase with longitude with |l|<1.5 deg, which is likely associatedwith the inner bar, and the other feature having considerably eccentricvelocities more than those of the normal x_1-orbit family feature. Theextinction-corrected K magnitudes (if used as a distance modulus) tend to showa sequential deposition of these objects along the line of sight toward theGalactic center depending on their radial velocities. The tendency thatappeared in the distance measures is consistent with the bulge-bar dynamicalmodel utilizing the periodic orbit families in the bar potential.