C.D.S. - SIMBAD4 rel 1.7 - 2020.12.03CET18:14:50

2007A&A...464.1023P - Astronomy and Astrophysics, volume 464, 1023-1027 (2007/3-4)

The interpretation of water emission from dense interstellar clouds.


Abstract (from CDS):

Existing SWAS observations and future HIFI/Herschel data require a clear sense of the information content of water emission and absorption lines. We investigate whether the ground-state transition of ortho-H2O (110->101) at 557GHz can be used to measure the column density throughout an interstellar cloud. We make use of a multi-zone escape probability code suitable for treating molecular line emission. For low abundances, i.e., X(H2O)≲10–9, the intensity of the 110->101 transition scales with the total column density of H2. However, this relationship breaks down with increasing abundance, i.e., optical depth, due to line trapping and - for Tdust>25K, X(H2O)≲10–8 and n∼104cm–3 - absorption of the dust continuum. An observed decline in intensity per column density, expected if H2O is a surface tracer, does not necessarily mean that the water is absent in the gas phase at large column densities, but can be caused by line trapping and subsequent collisional de-excitation. To determine the amount of water vapor in the interstellar medium, multiple line measurements of optically thin transitions are needed to disentangle radiative transfer and local excitation effects.

Abstract Copyright:

Journal keyword(s): ISM: molecules - radiative transfer - ISM: dust, extinction

Simbad objects: 4

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Number of rows : 4

N Identifier Otype ICRS (J2000)
ICRS (J2000)
Mag U Mag B Mag V Mag R Mag I Sp type #ref
1850 - 2021
1 NAME OMC1 Ridge reg 05 35 13.4 -05 23 07           ~ 123 0
2 M 42 HII 05 35 17.3 -05 23 28           ~ 3757 0
3 NAME Ori A MoC 05 38 -07.1           ~ 2707 0
4 NAME ORI MOL CLOUD MoC 05 56 -01.8           ~ 870 1

    Equat.    Gal    SGal    Ecl

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