Hot stars and cool clouds: the photodissociation region M16

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dc.contributor.author Levenson, Nancy en_US
dc.contributor.author Graham, James en_US
dc.contributor.author McLean, Ian en_US
dc.contributor.author Becklin, Eric en_US
dc.contributor.author Figer, Donald en_US
dc.contributor.author Gilbert, Andrea en_US
dc.contributor.author Larkin, James en_US
dc.contributor.author Teplitz, Harry en_US
dc.contributor.author Wilcox, Mavourneen en_US
dc.date.accessioned 2006-06-12T15:31:05Z en_US
dc.date.available 2006-06-12T15:31:05Z en_US
dc.date.issued 2000-04-10 en_US
dc.identifier.citation Astrophysical Journal Letters 533N1 (2000) L53-L56 en_US
dc.identifier.issn 1538-4357 en_US
dc.identifier.uri http://hdl.handle.net/1850/1990 en_US
dc.description Also archived in: arXiv:astro-ph/0002491 v1 26 Feb 2000 en_US
dc.description.abstract We present high-resolution spectroscopy and images of a photodissociation region (PDR) in M16 obtained during commissioning of NIRSPEC on the Keck II telescope. PDRs play a significant role in regulating star formation, and M16 offers the opportunity to examine the physical processes of a PDR in detail. We simultaneously observe both the molecular and ionized phases of the PDR and resolve the spatial and kinematic differences between them. The most prominent regions of the PDR are viewed edge-on. Fluorescent emission from nearby stars is the primary excitation source, although collisions also preferentially populate the lowest vibrational levels of H2. Variations in density-sensitive emission line ratios demonstrate that the molecular cloud is clumpy, with an average density n = 3 × 105 cm−3. We measure the kinetic temperature of the molecular region directly and find TH2 = 930 K. The observed density, temperature, and UV flux imply a photoelectric heating efficiency of 4%. In the ionized region, ni = 5×103 cm−3 and THii = 9500 K. In the brightest regions of the PDR, the recombination line widths include a non-thermal component, which we attribute to viewing geometry. (Refer to PDF file for exact formulas). en_US
dc.description.sponsorship Data presented herein were obtained at the W.M. Keck Observatory, which is operated as a scientific partnership among the California Institute of Technology, the University of California and the National Aeronautics and Space Administration. The Observatory was made possible by the generous financial support of the W.M. Keck Foundation. en_US
dc.format.extent 190659 bytes en_US
dc.format.mimetype application/pdf en_US
dc.language.iso en_US en_US
dc.publisher University of Chicago Press: Astrophysical Journal Letters en_US
dc.relation.ispartofseries vol. 533 en_US
dc.relation.ispartofseries no. 1 en_US
dc.relation.ispartofseries part 2 en_US
dc.relation.ispartofseries pps. L53-L56 en_US
dc.subject Stars-infrared en_US
dc.subject ISM-lines and bands en_US
dc.subject ISM-individual (M16) en_US
dc.subject Molecular processes en_US
dc.title Hot stars and cool clouds: the photodissociation region M16 en_US
dc.type Article en_US

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