Positions of hydroxyl masers at 1665 and 1667 MHz

Abstract

The Australia Telescope Compact Array has been used to observe more than 200 1665‐MHz hydroxyl masers south of declination −16° and derive their positions with typical rms uncertainties of 0.4 arcsec. Many of the 1665‐MHz maser sites are found to have 1667‐MHz OH maser counterparts which are coincident, within the errors. The resulting position list presented here includes all well‐documented, previously reported 1665‐MHz masers close to the Galactic plane in the galactic longitude range 230° (through 360°) to 13°. Nearly 50 newly discovered masers are also listed, chiefly in the longitude range 312° to 356°, where the observations were conducted as an intensive survey of a continuous zone close to the Galactic plane. Many of the maser sites are discussed briefly so as to draw attention to those possessing properties that are unusual among this large sample. Most of the masers are of the variety found in star‐forming regions – at the sites of newly formed massive stars and their associated ultracompact H ii regions. The new, accurate, positions reveal coincidences of the OH masers with the continuum radio emission, with the infrared emission from dust that accompanies such regions, and with emission from other maser species such as methanol at 6668 MHz and water at 22 GHz. By‐products of the survey, also presented here, include measurements of at least 11 objects that are not associated with massive star‐forming regions. They comprise several OH/IR stars (detected at the 1667‐ or 1665‐MHz transition of OH, though commonly found to be most prominent at the 1612‐MHz transition) and several unusual masers that may pinpoint other varieties of late‐type stars or protoplanetary nebulae.

12.2-GHz methanol maser MMB follow-up catalogue – IV. Longitude range 20°–60°

“…Like these rarer types of methanol masers, excited-state OH masers are more likely to be found towards sources showing 12.2-GHz masers, meaning that they are detected towards a subset of the more evolved 6.7-GHz methanol masers, but their occurrence is not as closely linked to the 6.7-and 12.2-GHz methanol maser luminosities. This result is also reflected in a comparison between the occurrence of 1665-and 1667-MH OH masers (Caswell 1998) with 6.7-and 12.2-GHz methanol maser sources .…”

A search for water masers associated with class II methanol masers – II. Longitude range 341° to 6°

“…Column 15 of Table 1 lists the associations with 12.2-GHz methanol and OH masers from Breen et al (2012); Caswell (1998) and Caswell et al (2013). Note that the 12.2-GHz associations are complete, coming from targeted observations towards the MMB sources.…”

Infall, outflow, and turbulence in massive star-forming cores in the G333 giant molecular cloud

“…From observations with the VLT MIR VISIR camera, Grave et al (2014) found indications that this region consists of two main luminous sources (O4V and O5V) which account for at least half of the luminosity from this region. As well as being proximate to the Hii region G333.6-0.22, this molecular outflow source is also associated with MSX and 1.2-mm dust sources (Mookerjea et al 2004) and masers of H 2 O and OH (Batchelor et al 1980;Caswell 1998).…”

“…The Mopra beam is 36 arcseconds at 3-mm wavelengths. The references are: (a) Mookerjea et al (2004); (b) Becklin et al (1973); (c) Murphy et al (2010); (d) Figuerêdo et al (2005); (e) Breen et al (2007); (f) Caswell (1998); (g) Caswell et al (1995). Ladd et al (2005) and the beam efficiencies used are as listed there.…”