A search for H₂ emission in bipolar nebulae and regions of interstellar shock

Phillips, J. P.; White, G. J. and Harten, R. (1985). A search for H₂ emission in bipolar nebulae and regions of interstellar shock. Astronomy & Astrophysics, 145(1) pp. 118–126.

URL: http://adsabs.harvard.edu/full/1985A&A...145..118P

Abstract

We report a H₂ emission survey of five bipolar outflow sources (NGC 1333, M2-9, As 353, S106, V645 Cyg), and one region of shock interaction between an H II region and molecular cloud (NGC 281). Two of the sources (M2-9, NGC 1333) were detected in the v = 1-0S(1), and Q-branch transitions of H₂, and we provide a detailed analysis and modelling for these cases. The probable mass of shocked H₂ is shown to range between 1.4 10^-6 and 4.2 10^-8 M_⊙ for M2-9, and ≈ 2.5^-4 and 1.9^-10 M_⊙ in the case of NGC 1333, although the latter values may require increasing by a factor of a few when due allowance is made for extinction. A detailed analysis for the core of M2-9 indicates that the ionized zone is extremely compact, and our Brackett line measures support other evidence in suggesting a high core extinction, large emission measure E~4 10¹⁰ cm^-6 pc, and a projected angular radius θ_c~0.04. Similarly, it is apparent from the H₂S(1) line strength that the core expansion velocity must be low and less than ~ 1 km s^-1 (a constraint which is also required on dynamical grounds). Finally, CO J = 3-2 observations of the source failed to detect emission above a 2σ limit of T^*_R ~ 0.4 K, and this is shown to imply a probable expansion timescale of ≲2 10³ yr.

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