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Up: New detections of OH


1 Introduction

Validity of OH maser emission as a powerful tool to identify protostellar objects has been demonstrated in several surveys (Turner 1979; Caswell & Haynes 1983a, 1983b; Cohen et al. 1988). Those observations are mainly confined to the galactic plane or strong FIR objects. Nevertheless, some galactic plane surveys were not carried out at a uniform grid of positions (Turner 1979), while objects at high galactic latitudes were rarely observed (Cohen et al. 1988; Slysh et al. 1994). With the release of IRAS catalogue the possibility to get a better statistics on sites of star-forming molecular clouds signposted by OH masers greatly increased (Cohen et al. 1988; Slysh et al. 1994; Slysh et al. 1997).

The discovery of the 6.7 GHz methanol maser emission (Menten 1991) has offered another promising way to investigate the very early stages in the formation of massive stars and to obtain more accurate distribution and kinematics of those objects in the Galaxy. The first large surveys of the methanol masers guided by OH maser catalogues quickly established a tight association between maser lines of both molecules (Menten 1991; Caswell et al. 1995). However, a search for the OH 1.6 GHz masers towards the CH3OH 6.7 GHz masers revealed that the substantial number of methanol sources did not associate OH maser emission (Gaylard et al. 1994). Several new detections of the methanol masers in the northern hemisphere (Slysh et al. 1999; Szymczak et al. 2000) offer a possibility to extend the population of OH masers and to learn more about relationships between the 6.7 GHz methanol emission and the OH maser emission at 1665 and 1667 MHz. In this paper we report the results of OH mainline observations in the direction of recently discovered methanol sources. The differences in infrared properties of the detections and non-detections are shortly discussed.


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Up: New detections of OH

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