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The filamentary structure of the interface between the atomic and the molecular phases in NGC7023

A.Fuente, J.Martín-Pintado, R.Neri, C.Rogers, G.Moriarty-Schieven
Centro Astronómico de Yebes (IGN), Apdo. 148, E-19080 Guadalajara, Spain
Institut de Radioastronomie Millimétrique, 300 rue de la Piscine, 38406 St-Martin-d'Heères, France
Dominion Radio Astrophysical Observatory, Herzberg Institue of Astrophysics, National Research Council of Canada, P.O. box 248, Penticton, BC, V2A 6K3, Canada
Abstract:

 

 


Figure: An HCO J=10 mosaic of the line emission towards the reflection nebula NGC 7023. The filamentary structures are regions of enhanced hydrogen density located in a narrow ridge () North-West from HD 200775 at the interface between the molecular and the atomic regions. Contours are from 100 mJy to 700 mJy in steps of 100 mJy. The velocity is marked on the top-left corner of the panels.

The combination of interferometric and single-dish data allow us, for the first time, to determine the intimate structure of the photodissociation region associated with the prototypical reflection nebula NGC 7023. We have mapped the J=10 HCO line using the IRAM millimeter interferometer and the 30-m single dish telescope, and the 21cm HI line using the Very Large Array of NRAO. The interferometric HCO data show the existence of four high density molecular filaments with different velocities (1.9 kms, 2.4 kms, 2.9 kms, 4.0 kms) located at the interface between the atomic and the molecular gas. An additional filament has been tentatively detected at 5.8 kms. From the comparison between the single-dish and the interferometric HCO data with HI emission, we derive that the filament at 4.0 kms and, very likely, that at 5.8 kms are located on the inner walls of the HI clump, immersed in an atomic medium, while those at 1.9 and 2.4 kms are immersed in the molecular cloud. The filament at 2.9 kms would be located in an intermediate zone. The thickness of the filaments are and the derived densities vary between and a few cm. The molecular filaments match perfectly the infrared filaments found at 2.1 m, suggesting that infrared and millimeter data are probing regions of enhanced hydrogen density.


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Next: New Preprints Up: Scientific results Previous: Interferometric molecular line



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