Astron. Astrophys. 323, 529-533 (1997)

Research Note

Intense molecular emission from the Lagoon nebula, M8

Glenn J. White ¹, N.F.H. Tothill ¹, H.E. Matthews ², W.H. McCutcheon ³, M. Huldtgren ⁴ and Mark J. McCaughrean <sup>5, 6

1</sup> Department of Physics, Queen Mary & Westfield College, University of London, Mile End Road, London E1 4NS, UK
² Joint Astronomy Centre, 660 N A'hku Place, University Park, Hilo, Hawaii 96720, USA
³ Department of Physics and Astronomy, University of British Columbia, Vancouver, British Columbia V6T 1Z1, Canada
⁴ Stockholm Observatory, S-133 36 Saltsjöbaden, Sweden
⁵ Max-Planck-Institut für Astronomie, Königstuhl, D-69117 Heidelberg, Germany
⁶ Max-Planck-Institut für Radioastronomie, Auf dem Hügel 69, D-53121 Bonn, Germany

Received 21 January 1997 / Accepted 21 March 1997

Abstract

The discovery is reported of the second strongest source of mm and submm wavelength CO line emission, towards M8, the Lagoon Nebula in Sagittarius. The 31 molecular core has dimensions 0.2 0.3 pc and is centred on the O7V star Herschel 36 (H 36), near the Hourglass Nebula in the core of M8. Emission from the CO line wings extends to the north and south of the Hourglass, although a lack of near-IR H₂ emission indicates that outflow activity is much less prominent than in many active star-formation regions, and suggests that the CO line wings may trace the expanding edge of a cavity around H 36. The molecular line data are compared with new near-IR narrow-band, continuum-subtracted images in He I, H₂, and H (Br ) lines and archival HST emission-line images in H , [O III], and [S II]. The optical and near-IR data are found to be broadly consistent with previous photo-ionisation models of the Hourglass, which is excited by H 36. However, there are variations in the He I/Br line ratio which are difficult to explain.

Key words: ISM: individual objects: M8 ISM: molecules radio lines: ISM

Send offprint requests to: Prof Glenn White

SIMBAD Objects

Contents

• 1. Introduction
• 2. The Observations
• 3. Molecular and CI line data
• 4. Infrared and optical data
• 5. Conclusions
• Acknowledgements
• References

© European Southern Observatory (ESO) 1997

Online publication: June 5, 1998

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