The 6-GHz methanol multibeam maser catalogue - I. Galactic Centre region, longitudes 345? to 6?
Date
2010
Authors
Caswell, J.L.
Phillips, C
Fuller, G.A.
Green, J A
Avison, A
Breen, S.L.
Burton, Michael Graham
Chrysostomou, A
Cox, J
Diamond, Philip John
Journal Title
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Volume Title
Publisher
Oxford University Press
Abstract
We have conducted a Galactic plane survey of methanol masers at 6668 MHz using a sevenbeam receiver on the Parkes telescope. Here we present results from the first part, which
provides sensitive unbiased coverage of a large region around the Galactic Centre. Details are
given for 183 methanol maser sites in the longitude range 345◦ through the Galactic Centre to
6◦. Within 6◦ of the Galactic Centre, we found 88 maser sites, of which more than half (48)
are new discoveries. The masers are confined to a narrow Galactic latitude range, indicative
of many sources at the Galactic Centre distance and beyond, and confined to a thin disc
population; there is no high-latitude population that might be ascribed to the Galactic bulge.
Within 2◦ of the Galactic Centre the maser velocities all lie between −60 and +77 km s−1,
a range much smaller than the 540 km s−1 range observed in CO. Elsewhere, the maser with
highest positive velocity (+107 km s−1) occurs, surprisingly, near longitude 355◦ and is probably attributable to the Galactic bar. The maser with the most negative velocity (−127 km s−1)
is near longitude 346◦, within the longitude–velocity locus of the near side of the ‘3-kpc arm’.
It has the most extreme velocity of a clear population of masers associated with the near and
far sides of the 3-kpc arm. Closer to the Galactic Centre the maser space density is generally
low, except within 0.25 kpc of the Galactic Centre itself, the ‘Galactic Centre zone’, where
it is 50 times higher, which is hinted at by the longitude distribution, and confirmed by the
unusual velocities.
Description
Keywords
ISM: molecules, Masers, Stars: formation, Surveys
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Source
Monthly Notices of the Royal Astronomical Society
Type
Journal article
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Access Statement
Open Access
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Restricted until
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