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

Abstract

A survey has been made in the SiO J \ 1È0, v \ 1 and 2 transitions (D43 GHz) for color-selected IRAS sources in the Galactic-center region of o l o ¹ 3¡ and o b o ¹ 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 km Ñux 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 and km s~1, which is interpreted as an underl \ [0¡ .4È1¡ .0 V lsr \ 20È150 sampling e †ect 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 Ðtting 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 o b o [ 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.

Near-IR Observations of IRAS Sources with SiO Masers at the Inner Galactic Bulge

“…• and |b| < 3 • ); SiO maser lines were detected for all of these sources (Deguchi et al 2000a). This IRAS sample was chosen using well-defined intensity and color criteria: F 12 > 2 Jy and 0 < C 12 ≡ log(F 25 /F 12 ) < 0.1, where F 12 and F 25 are the IRAS 12 and 25 µm flux densities.…”

“…The results are given in table 3. The galactic coordinates, the distance from the Sun to the source, the distance from the Galactic center to the source, the extinction in the K-band, the bolometric corrections from the formulae of van der Veen and Breukers (1989) and the present paper, and the SiO radial velocity (taken from Deguchi et al 2000a) are also given. In table 3, we have included all of the sources, including those in table 2 involving dubious, multiple, and overlapped candidates.…”

“…We have excluded the exceptional bright source 17482−2824, with F 12 = 428 Jy from the analysis. This source was originally included in the sample for completeness of the survey (Deguchi et al 2000a). Figure 7 shows the l-V LSR diagram for this sample.…”

Relation of S[CLC]i[/CLC]O Maser Emission to Infrared Radiation in Evolved Stars Based on the [ITAL]Midcourse Space Experiment[/ITAL] Observation

“…The combination of a large antenna and a sensitive detector at 43 GHz in this system made it feasible to detect an SiO maser emission of the -0 rotational transition as weak as 0.2 K. Since J p 1 1992 (Nakada et al 1993), this system has been used to observe thousands of the IRAS Point Source Catalog (PSC) sources that are candidates for evolved stars defined by their IRAS colors and has detected about 500 new SiO maser objects during the surveys of the bulge (Izumiura et al 1994(Izumiura et al , 1995a(Izumiura et al , 1995b, the inner disk (Izumiura et al 1999;Deguchi et al 2000aDeguchi et al , 2000b, the outer disk (Jiang et al 1996, Jiang, Deguchi, & Ramesh 1999, and the northern pole (Ita et al 2001).…”

“…The SiO maser data in this study are compiled from Izumiura et al (1994Izumiura et al ( , 1995aIzumiura et al ( , 1995bIzumiura et al ( , 1999, Deguchi et al (2000b), and Jiang et al (1996Jiang et al ( , 1999, and consist mostly of sources in the Galactic plane. These studies achieved approximately the same detection limit, with sensitivity of about 0.15 K at a 5 j level that varies slightly depending on the system condition, weather, etc.…”