The Lagoon Nebula and its Vicinity - AstrophysicsReport as inadecuate

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Abstract: The Lagoon Nebula is an HII region in the Sagittarius Arm, about 1.3 kpcaway, associated with the young 1-3 Myr open cluster NGC 6530, which containsseveral O stars and several dozen B stars. Lower-mass cluster members, detectedby X-ray and H-alpha emission, and by near-IR excess, number more than athousand. Myr-old star formation is traced by the optically-visible HII regionand cluster; observations of infrared and submillimetre-wave emission, and ofoptical emission features, indicate ongoing star formation in several locationsacross the Lagoon. The most prominent of these are the Hourglass Nebula andM8E. Submillimetre-wave observations also reveal many clumps of dense moleculargas, which may form the next generation of stars. The complex structure of theregion has been shaped by the interaction of the underlying molecular gas withmultiple massive stars and episodes of star formation. NGC 6530 is the oldestcomponent, with the newest stars found embedded in the molecular gas behind thecluster and at its southern rim. A degree to the east of the Lagoon, Simeis 188is a complex of emission and reflection nebulae, including the bright-rimmedcloud NGC 6559; the presence of H-alpha emission stars suggests ongoing starformation.

Author: N. F. H. Tothill U. Exeter, UK, Marc Gagné West Chester U., USA, B. Stecklum Tautenburg, Germany, M. A. Kenworthy U. Arizona, US


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