A survey of 557 GHz water vapor emission in the NGC 1333 molecular cloud

Authors

EA Bergin
MJ Kaufman
GJ Melnick
Ronald L. Snell, University of Massachusetts - AmherstFollow
JE Howe

Publication Date

2003

Journal or Book Title

ASTROPHYSICAL JOURNAL

Abstract

Using NASA's Submillimeter Wave Astronomy Satellite (SWAS), we have examined the production of water in quiescent and shocked molecular gas through a survey of the 556.936 GHz 1₁₀-1₀₁ transition of ortho-H₂O in the NGC 1333 molecular core. These observations reveal broad emission lines associated with the IRAS 2, IRAS 4, IRAS 7, and HH 7-11 outflows. Toward three positions we detect narrow (Δv ~ 2-3 km s^-1) emission lines clearly associated with the ambient gas. The SWAS observations, with a resolution of ~4', are supplemented with observations from the Infrared Space Observatory (ISO) and by an unbiased survey of a ~17' × 15' area, with ~50'' resolution, in the low-J transitions of CO, ¹³CO, C¹⁸O, N₂H⁺, CH₃OH, and SiO. Using these combined data sets, with consistent assumptions, we find beam-averaged ortho-H₂O abundances of greater than 10^-6 relative to H₂ for all four outflows. A comparison of SWAS and ISO water data is consistent with nondissociative shock models, provided the majority of the ortho-H₂O (1₁₀-1₀₁) emission arises from cool postshock material with enhanced abundances. In the ambient gas the ortho-H₂O abundance is found to lie between 0.1 × 10^-7 and 1 × 10^-7 relative to H₂ and is enhanced when compared to cold prestellar molecular cores. A comparison of the water emission with tracers of dense condensations and shock chemistry finds no clear correlation. However, the water emission appears to be associated with the presence of luminous external heating sources that power the reflection nebula and the photodissociation region (PDR). Simple PDR models are capable of reproducing the water and high-J ¹³CO emission, suggesting that a PDR may account for the excitation of water in low-density undepleted gas, as suggested by Spaans & van Dishoeck.

Comments

This is the pre-published version harvested from ArXiv. The published version is located at http://iopscience.iop.org/0004-637X/582/2/830/

DOI

https://doi.org/10.1086/344674

Pages

830-845

Volume

582

Issue

2

Recommended Citation

Bergin, EA; Kaufman, MJ; Melnick, GJ; Snell, Ronald L.; and Howe, JE, "A survey of 557 GHz water vapor emission in the NGC 1333 molecular cloud" (2003). ASTROPHYSICAL JOURNAL. 621.
https://doi.org/10.1086/344674