Ammonia observations of bright-rimmed clouds: establishing a sample of triggered protostars - Astrophysics > Astrophysics of GalaxiesReport as inadecuate




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Abstract: We observed 42 molecular condensations within previously identifiedbright-rimmed clouds in the ammonia rotational inversion lines NH3 1,1,2,2, 3,3 and 4,4 using the Green Bank Telescope in Green Bank, WestVirginia. Using the relative peaks of the ammonia lines and their hyperfinesatellites we have determined important parameters of these clouds, includingrotational temperatures and column densities.These observations confirm the presence of dense gas towards IRAS pointsources detected at submillimetre wavelengths. Derived physical propertiesallow us to refine the sample of bright-rimmed clouds into those likely to besites of star formation, triggered via the process of radiatively-drivenimplosion. An investigation of the physical properties of our sources show thattriggered sources are host to greater turbulent velocity dispersions, likelyindicative of shock motions within the cloud material. These may be attributedto the passage of triggered shocks or simply the association of outflowactivity with the sources.In all, we have refined the Sugitani et al. 1991 catalogue to 15 cloudswhich are clearly star-forming and influenced by externalphotoionisation-induced shocks. These sources may be said, with highconfidence, to represent the best examples of triggering within bright-rimmedclouds.



Author: L.K. Morgan, C.C. Figura, J.S. Urquhart, M.A. Thompson

Source: https://arxiv.org/







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