Journal Article

Spectral imaging of the Sagittarius B2 region in multiple 7-mm molecular lines

P. A. Jones, M. G. Burton, N. F. H. Tothill and M. R. Cunningham

in Monthly Notices of the Royal Astronomical Society

Published on behalf of The Royal Astronomical Society

Volume 411, issue 4, pages 2293-2310
Published in print March 2011 | ISSN: 0035-8711
Published online March 2011 | e-ISSN: 1365-2966 | DOI:
Spectral imaging of the Sagittarius B2 region in multiple 7-mm molecular lines

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We have undertaken a spectral-line imaging survey of a 6 × 6 arcmin2 area around Sagittarius (Sgr) B2 near the centre of the Galaxy, in the range from 30 to 50 GHz, using the Mopra telescope. The spatial resolution varies from 1.0 to 1.4 arcmin and the spectral resolution varies from 1.6 to 2.7 km s−1 over the frequency range. We present velocity-integrated emission images for 47 lines: 38 molecular lines and nine radio recombination lines.

There are significant differences between the distributions of different molecules, in part due to spatial differences in chemical abundance across the complex. For example, HNCO and HOCO+ are found preferentially in the north cloud, and CH2NH near Sgr B2 (N). Some of the differences between lines are due to excitation differences, as shown by the 36.17- and 44.07-GHz lines of CH3OH, which have maser emission, compared to the 48.37-GHz line of CH3OH. Other major differences in integrated molecular line distribution are due to absorption of the 7-mm free–free continuum emission (spatially traced by the radio recombination line emission) by cool intervening molecular material, causing a central dip in the molecular line distributions.

These line distribution similarities and differences have been statistically described by Principal Component Analysis and interpreted in terms of simple Sgr B2 physical components of the cooler, lower density envelope, and dense, hot cores Sgr B2 (N), (M) and (S).

Keywords: ISM: individual objects: Sagittarius B2; ISM: kinematics and dynamics; ISM: molecules; radio lines: ISM

Journal Article.  11780 words.  Illustrated.

Subjects: Astronomy and Astrophysics

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