Astron. Astrophys. 336, 1007-1023 (1998)

Studies of dense cores in regions of massive star formation

VI. Multitransitional CS and CO observations of G 261.64-2.09, G 268.42-0.85, G 270.26+0.83 and G 301.12-0.20

A.V. Lapinov ¹, P. Schilke ², M. Juvela ³ and I.I. Zinchenko <sup>1, 3

1</sup> Institute of Applied Physics of the Russian Academy of Sciences, Uljanov str. 46, 603600 Nizhny Novgorod, Russia
² Max-Planck-Institut für Radioastronomie, Auf dem Hügel 69, D-53121 Bonn, Germany
³ Helsinki University Observatory, Tähtitorninmäki, P.O. Box 14, FIN-00014 University of Helsinki, Finland

Received 31 July 1997 / Accepted 24 April 1998

Abstract

We report the results of a multitransitional study of four southern molecular clouds in the CS , , , ; CO , ; C³⁴S and C¹⁸O lines observed with SEST and CSO telescopes. To analyze the obtained maps we applied a MEM deconvolution technique which improves the resolution significantly, if the signal-to-noise ratio is sufficiently high. We compare the molecular line maps with available infrared and molecular maser data and for G 268.42-0.85 also with optical DSS image. Two of four cores (G 268.42-0.85 and G 301.12-0.20) show bipolar structure in CS with blue- and red-shifted peaks symmetrically displaced relative the central IR objects. We found that in all observed regions the deconvolved source size decreases sharply with the quantum number of the rotational transition, and the measured FWHP of the CS lines decreases with radius. From optically thin C¹⁸O lines we estimate the H₂ column densities to be of the order of 10²³cm^-2 and from C³⁴S the fractional abundance of CS as .

Key words: stars: formation ISM: clouds ISM: molecules radio lines: ISM

Send offprint requests to: A.V. Lapinov, (lapinov@appl.sci-nnov.ru)

SIMBAD Objects

Contents

• 1. Introduction
• 2. Observations
• 3. Data reduction
• 4. Results and comparison with previous observations
  • 4.1. General morphology of observed regions
  • 4.2. G 261.64-2.09
  • 4.3. G 268.42-0.85 (BBW 222)
  • 4.4. G 270.26+0.83 (RCW 41, BBW 246)
  • 4.5. G 301.12-0.20
• 5. Parameters estimation
  • 5.1. Peak temperatures, sizes and line widths
  • 5.2. CS opacities and column densities
  • 5.3. N_L(H₂) and X(CS) estimates
• 6. Conclusions
• Acknowledgements
• References

© European Southern Observatory (ESO) 1998

Online publication: July 27, 1998
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