SiO maser survey of AGB stars in the North Galactic Cap^*

¹ Institute of Astronomy, School of Science, The University of Tokyo, 2-21-1 Osawa, Mitaka, Tokyo 181-0015, Japan
² Nobeyama Radio Observatory, National Astronomical Observatory, Minamimaki, Minamisaku, Nagano 384-1305, Japan
³ VERA project office, National Astronomical Observatory, Mitaka, Tokyo 181-8588, Japan
⁴ Mizusawa Astrogeodynamics Observatory, National Astronomical Observatory, Mizusawa, Iwate 023-0861, Japan
⁵ Kiso Observatory, School of Science, The University of Tokyo, Mitake, Kiso, Nagano 397-0101, Japan
⁶ Department of Astronomical Science, The Graduate University for Advanced Studies, Nobeyama Radio Observatory, National Astronomical Observatory, Minamimaki, Minamisaku, Nagano 384-1305, Japan
⁷ National Astronomical Observatory, 2-21-1 Osawa, Mitaka, Tokyo 181-8588, Japan
⁸ Indian Institute of Astrophysics, Bangalore 560034, India

Corresponding author: Y. Ita, yita@mtk.ioa.s.u-tokyo.ac.jp

Received: 4 December 2000
Accepted: 1 June 2001

Abstract

A SiO maser survey in the , and 2 transitions has been made for IRAS sources in the North Galactic Cap (b > 30°) with the Nobeyama 45 m radio telescope. The sources were selected on the basis of their IRAS 12/25-m and 25/60-m flux ratios as likely oxygen-rich AGB candidates. SiO masers were detected from 24 out of the 97 selected sources, where 17 were new detections. The distances and heights above the Galactic plane are calculated. The Galactic distribution of detected and undetected stars indicates that metallicity is likely to govern the detection rate. The Galactocentric angular velocities of the subsampled stars are derived and their variation with the Galactic height is discussed.