Introduction

The sample of CO outflows reported in Bally & Lada (1983) was searched for OH maser emission (Prestwich 1985). The stronger OH maser sources found in this search – augmented by two other sources – were then mapped using MERLIN. The maser distributions were compared with the molecular emission from the sources.

A clear-cut case of the association between OH maser emission and a molecular disc is found in G35.2-0.7N (Brebner et al. 1987). Its bipolar outflow is well collimated and an ammonia condensation is observed, clearly elongated in a direction perpendicular to the outflow direction. The OH masers are situated at, or near the exciting source of the region, and lie in an elongated distribution with an orientation which reflects that of the larger-scale ammonia disc.

Comparison of OH maser and CO outflow distributions

Comparisons could be made for eight sources – the masers in Orion-KL were mapped by Norris (1984). As observations of a molecular disc were unclear, or had not yet been attempted in many cases, a comparison was made between the orientations of the CO outflows and the OH maser distributions. The major axis of the OH maser distribution was deduced from a least squares fit and the angular differences between maser and outflow orientations are shown in (Figure 1). The largest source of error is in the estimates of the outflow direction, many of which had to be made by eye. (A selection effect is inherent: the sample could not have face-on discs, since the CO outflow direction could not be identified in such cases.)