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Molecular line survey of Sagittarius B2(M) from 330 to 355 GHz and comparison with Sagittarius B2(N)

Sutton, E. C. and Jaminet, P. A. and Danchi, W. C. and Blake, Geoffrey A. (1991) Molecular line survey of Sagittarius B2(M) from 330 to 355 GHz and comparison with Sagittarius B2(N). Astrophysical Journal Supplement Series, 77 (2). pp. 255-285. ISSN 0067-0049.

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We have surveyed molecular line emission from Sgr B2 over the range from 330 to 355 GHz at the position designated Sgr B2(M). This position is prominent in millimeter continuum maps of the region and is associated with a compact H II region, a hot NH_3 core, and sources of H_2O and OH maser emission. We have also obtained observations contrasting the submillimeter molecular emission from Sgr B2(M) and Sgr B2(N), an additional center of activity thought to be a dense protostellar core. The picture of the interstellar chemistry of these regions which we derive is substantially different from that determined from previous observations at lower frequencies and with lower spatial resolution. In particular, molecules such as SO_2 and CH_3OH dominate the submillimeter spectrum to a much greater extent than they do the low-frequency observations. Much of this difference is due to the higher spatial resolution of the submillimeter observations, which makes them much more sensitive to emission from compact, dense cores. The millimeter data were most effective at sampling material in the surrounding lower density regions. The chemistry of the core sources in Sgr B2 appears similar to that of other dense cores, such as the core of the Orion molecular cloud. The spectral differences between Sgr B2(M) and Sgr B2(N) primarily relate to differences in excitation and column density. For most molecular species the northern source (N) has a column density significantly higher than that found in the middle source (M), often by a factor of about 5. The principal exceptions are the species SO and SO_2 which seem to be substantially more abundant in the middle source. Generally excitation seems to be higher in the northern source, suggesting a somewhat higher density core, although there are some departures indicating that the excitation situation is more complicated. High optical depths in many of the submillimeter transitions systematically bias the interpretation of both column densities and excitation. Many of the millimeter lines may also have high optical depths, particularly those lines arising from the compact core sources.

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Blake, Geoffrey A.0000-0003-0787-1610
Additional Information:© 1991 American Astronomical Society. Provided by the NASA Astrophysics Data System. Received 1990 December 4, accepted 1991 March 26. This work has been supported in part by the National Science Foundation under grants AST-8715295, AST- 8818327, and AST-9196077. One of the authors (W. C. D.) has received funding through the L. W. Frohlich Research Fellowship of the New York Academy of Sciences, and another (P. A. J.) has been supported by NASA's Graduate Student Researchers Program. G. A. B. would like to thank the David and Lucille Packard and Alfred P. Sloan Foundations for their support. Research at the Caltech Submillimeter Observatory has been funded by NSF grants AST-8311849 and AST-8815132. The James Clerk Maxwell Telescope is operated by the Royal Observatory Edinburgh on behalf of the Science and Engineering Research Council of the United Kingdom, the Netherlands Organization for Scientific Research, and the National Research Council of Canada. We are most grateful to Colin Masson and Antony Schinkel for their help with the CSO observations and to Adrian Russell and Goran Sandell for their assistance at the JCMT. This manuscript has benefited from helpful comments by L. E. Snyder and the referee, B. E. Turner.
Group:UNSPECIFIED, Division of Geological and Planetary Sciences
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New York Academy of SciencesUNSPECIFIED
NASA Graduate Student Research FellowshipUNSPECIFIED
David and Lucile Packard FoundationUNSPECIFIED
Alfred P. Sloan FoundationUNSPECIFIED
Subject Keywords:interstellar: abundances; interstellar: molecules; line identifications; masers; nebulae: individual (Sgr B2)
Issue or Number:2
Record Number:CaltechAUTHORS:20120918-082053852
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Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:34162
Deposited By: Ruth Sustaita
Deposited On:18 Sep 2012 16:09
Last Modified:03 Oct 2019 04:16

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