A CH3CN and HCO+ survey towards southern methanols masers associated with star formation

Purcell, C. R., Balasubramanyam, R., Burton, M. G., Walsh, A. J., Minier, V., Hunt-Cunningham, M. R., Kedziora-Chudczer, L. L., Longmore, S. N., Bains, I., Hill, T., Barnes, P. J., Busfield, A. L., Calisse, P., Crighton, N. H. M., Curran, S. J., Davis, T. M., Dempsey, J. T., Derragopian, G., Fulton, B., Hidas, M. G., Hoare, M. G., Lee, J.-K., Ladd, E. F., Lumsden, S. L., Moore, T. J. T., Murphy, M. T., Oudmaijer, R. D., Pracy, M. B., Rathborne, J., Robertson, S., Schultz, A. S. B., Shobbrook, J., Sparks, P. A., Storey, J. and Travouillion, T. (2006) A CH3CN and HCO+ survey towards southern methanols masers associated with star formation. Monthly Notices of the Royal Astronomical Society, 367 2: 553-576.

Author Purcell, C. R.
Balasubramanyam, R.
Burton, M. G.
Walsh, A. J.
Minier, V.
Hunt-Cunningham, M. R.
Kedziora-Chudczer, L. L.
Longmore, S. N.
Bains, I.
Hill, T.
Barnes, P. J.
Busfield, A. L.
Calisse, P.
Crighton, N. H. M.
Curran, S. J.
Davis, T. M.
Dempsey, J. T.
Derragopian, G.
Fulton, B.
Hidas, M. G.
Hoare, M. G.
Lee, J.-K.
Ladd, E. F.
Lumsden, S. L.
Moore, T. J. T.
Murphy, M. T.
Oudmaijer, R. D.
Pracy, M. B.
Rathborne, J.
Robertson, S.
Schultz, A. S. B.
Shobbrook, J.
Sparks, P. A.
Storey, J.
Travouillion, T.
Title A CH3CN and HCO+ survey towards southern methanols masers associated with star formation
Journal name Monthly Notices of the Royal Astronomical Society   Check publisher's open access policy
ISSN 0035-8711; 1365-8711; 1365-2966
Publication date 2006-04
Sub-type Article (original research)
DOI 10.1111/j.1365-2966.2005.09921.x
Volume 367
Issue 2
Start page 553
End page 576
Total pages 24
Place of publication London
Publisher Blackwell Scientific
Language eng
Subject 020110 Stellar Astronomy and Planetary Systems
Formatted abstract We present the initial results of a 3-mm spectral-line survey towards 83 methanol maser-selected massive star-forming regions. Here, we report observations of the J = 5–4 and 6–5 rotational transitions of methyl cyanide (CH3CN) and the J = 1–0 transition of HCO+ and H13CO+.

CH3CN emission is detected in 58 sources (70 per cent of our sample). We estimate the temperature and column density for 37 of these using the rotational diagram (RD) method. The temperatures we derive range from 28–166 K, and are lower than previously reported temperatures, derived from higher J transitions. We find that CH3CN is brighter and more commonly detected towards ultracompact H ii (UCH ii) regions than towards isolated maser sources. Detection of CH3CN towards isolated maser sources strongly suggests that these objects are internally heated and that CH3CN is excited prior to the UCH ii phase of massive star formation.

HCO+ is detected towards 82 sources (99 per cent of our sample), many of which exhibit asymmetric line profiles compared to H13CO+. Skewed profiles are indicative of inward or outward motions, however, we find approximately equal numbers of red- and blue-skewed profiles among all classes. Column densities are derived from an analysis of the HCO+ and H13CO+ line profiles.

80 sources have mid-infrared (mid-IR) counterparts: 68 seen in emission and 12 seen in absorption as 'dark clouds'. Seven of the 12 dark clouds exhibit asymmetric HCO+ profiles, six of which are skewed to the blue, indicating infalling motions. CH3CN is also common in dark clouds, where it has a 90 per cent detection rate.

Keyword surveys
stars: formation
stars: pre-main-sequence
ISM: abundances
H ii regions
ISM: molecules
Q-Index Code C1

Document type: Journal Article
Sub-type: Article (original research)
Collections: Excellence in Research Australia (ERA) - Collection
School of Mathematics and Physics
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