Maser maps and magnetic field of OH 300.969+1.147

• Published in: Monthly notices of the Royal Astronomical Society Vol. 398; no. 2; pp. 528 - 534
• Main Authors: Caswell, J. L., Kramer, B. Hutawarakorn, Reynolds, J. E.
• Format: Journal Article
• Language: English
• Published: Oxford, UK Blackwell Publishing Ltd 11-09-2009; Wiley-Blackwell; Oxford University Press
• Subjects: Astronomy; Earth, ocean, space; Exact sciences and technology; H ii regions; ISM: molecules; Magnetic fields; masers; Radio astronomy; radio lines: ISM; Star & galaxy formation; Stars & galaxies; stars: formation; Australia; H; stars: formation; regions; masers; radio lines: ISM; ISM: molecules; Ground states; Circular polarization; Excited states; HII regions; H II regions; Star formation; Masers; Transition state; Magnetic fields; Compact H II region; Diameter; Methanol
• ISSN: 0035-8711; 1365-2966
• DOI: 10.1111/j.1365-2966.2009.14952.x

The southern maser site OH 300.969+1.147 has been studied using the Long Baseline Array of the Australia Telescope National Facility. The 1665- and 1667-MHz hydroxyl ground-state transitions were observed simultaneously. A series of maps with 0.1-arcsec spatial resolution, at velocity spacing 0.09 km s−1, and in both senses of circular polarization reveals 59 small diameter maser spots. The spots are scattered over 2 arcsec, coincident with a strong ultracompact H ii region, at a distance of 4.3 kpc. 17 Zeeman pairs of oppositely polarized spots were found, all yielding magnetic field estimates towards us (negative), ranging from −1.1 to −4.7 mG, with a median value of −3.5 mG. Excited state masers of OH at 6035 and 6030 MHz at this site also display Zeeman pairs revealing a magnetic field of −5.0 mG. Weak methanol maser emission is intermingled with the OH masers, but there is no detectable closely related water maser. The consistent magnetic field direction found within this site is a striking feature of several other maser sites associated with strong H ii regions studied in comparable detail. We interpret the site as a mature region nearing the end of the brief evolutionary stage that can support maser emission.