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Detection of the 62 micron crystalline H2O ice feature in emission toward HH 7 with the Infrared Space Observatory long-wavelength spectrometer

Molinari, Sergio; Ceccarelli, Cecilia; White, Glenn J.; Saraceno, Paolo; Nisini, Brunella; Giannini, Teresa and Caux, Emmanuel (1999). Detection of the 62 micron crystalline H2O ice feature in emission toward HH 7 with the Infrared Space Observatory long-wavelength spectrometer. The Astrophysical Journal, 521(1) L71-L74.

DOI (Digital Object Identifier) Link: http://dx.doi.org/10.1086/312178
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Abstract

We report the detection of the 62 μm feature of crystalline water ice in emission toward the bow-shaped Herbig-Haro object HH 7. Significant amounts of far-infrared continuum emission are also detected between 10 and 200 μm, so that Herbig-Haro objects cease to be pure emission-line objects at far-infrared wavelengths. The formation of crystalline water ice mantles requires grain temperatures Tgr≳100 K at the time of mantle formation, suggesting that we are seeing material processed by the HH 7 shock front. The deduced ice mass is ~2 × 10-5 Mʘ, corresponding to a water column density N(H2O) ~ 1018 cm-2; an estimate of the [H2O]/[H] abundance yields values close to the interstellar gas-phase oxygen abundance. The relatively high dust temperature and the copious amounts of gas-phase water needed to produce the observed quantity of crystalline water ice suggest a scenario in which both dissociative and nondissociative shocks coexist. The timescale for ice mantle formation is of the order of ~400 yr, so that the importance of gas-phase water cooling as a shock diagnostic may be greatly diminished.

Item Type: Journal Article
Copyright Holders: 1999 The American Astronomical Society
ISSN: 1538-4357
Keywords: dust; extinction; continuum; lines and bands; Herbig-Haro objects; HH 7
Academic Unit/Department: Science > Physical Sciences
Interdisciplinary Research Centre: Centre for Earth, Planetary, Space and Astronomical Research (CEPSAR)
Item ID: 31821
Depositing User: Glenn White
Date Deposited: 10 Feb 2012 16:41
Last Modified: 28 Jan 2014 10:43
URI: http://oro.open.ac.uk/id/eprint/31821
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