Maser maps and magnetic field of OH 300.969+1.147 |
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| Authors: | J L Caswell B Hutawarakorn Kramer J E Reynolds |
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| Institution: | Australia Telescope National Facility, CSIRO, PO Box 76, Epping, NSW 2121, Australia;Max-Planck-Institut für Radioastronomie, Auf dem Hügel 69, 53121 Bonn, Germany;National Astronomical Research Institute of Thailand, Physics Building, Chiang Mai University, Chiang Mai 50200, Thailand |
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| Abstract: | 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. |
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| Keywords: | masers stars: formation H ii regions ISM: molecules radio lines: ISM |
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