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Astron. Astrophys. 346, 947-954 (1999)

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Expansion and turbulence in the Hourglass region of the Lagoon Nebula (M 8)

New [OIII]5007Å line observations

A. Chakraborty * and B.G. Anandarao

Physical Research Laboratory, Ahmedabad 380009, India

Received 30 December 1997 / Accepted 1 April 1999


We present new, seeing-limited Imaging Fabry-Perot spectroscopic observations in the [OIII]5007Å line in the Hourglass region of the Lagoon nebula. As many as 900 line profiles were obtained in a region of 1´[FORMULA]1´ surrounding the Hourglass, each one representing a spatial element of 2"[FORMULA]2". We find expansion of the HII region and high velocities upto -35 km s-1, which indicate Champagne flow. Our observations constrain the orientation of cavities in the Hourglass relative to the line of sight. We identify three kinematically distinct regions in and around the Hourglass. Further, we studied turbulence in the Hourglass region by computing the structure function using a larger set of data points at a resolution of 1". We find a power index of 0.46 for the structure function which is in variance with Kolmogoroff 's theory.

Key words: ISM: individual objects: M 8 – line: profiles – turbulence – ISM: kinematics and dynamics

* Present Address: Inter-University Centre for Astronomy and Astrophysics, Ganeshkhind, Pune - 411007, India (abhijit@iucaa.ernet.in)

Send offprint requests to: Anandarao (anand@prl.ernet.in)

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© European Southern Observatory (ESO) 1999

Online publication: June 17, 1999