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Astron. Astrophys. 351, 292-302 (1999)

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Ices and extinction through the Taurus and Ophiuchus clouds

T.C. Teixeira 1,2 and J.P. Emerson 1

1 Department of Physics, Queen Mary and Westfield College, Mile End Road, London E1 4NS, England, UK (j.p.emerson@qmw.ac.uk)
2 Institute of Physics and Astronomy, Å rhus University, Ny Munkegade, 8000 Å rhus C, Denmark (tct@obs.aau.dk)

Received 28 January 1999 / Accepted 19 August 1999

Abstract

A detailed intercomparison is made between published observations of H2O and CO ices towards the Taurus and Ophiuchus dark clouds. The column densities of the ices are intercompared, and each compared to the visual extinction through the clouds, [FORMULA]. It is neither clear that the two clouds have different or well defined threshold extinctions for the survival of ice mantles, nor that, for each of the clouds, the thresholds for the survival of CO and H2O mantles are different. The inclusion of new objects in Taurus (Teixeira et al. 1998) introduces a large scatter in the relations between those quantities relative to results obtained by previous authors. Lines-of-sight towards deeply embedded Young Stellar Objects in Taurus appear to show an enhancement in the amount of water-ice relative to lines-of-sight towards field stars behind that cloud. While for [FORMULA]mag there is a tight correlation between the water-ice column density, Ns(H2O), and [FORMULA], the inclusion of those new objects reveals a discontinuity in the relation between Ns(H2O) and [FORMULA]. The interpretation of this discontinuity is discussed.

Key words: stars: formation – ISM: clouds – ISM: dust, extinction – ISM: molecules – infrared: ISM: lines and bands

Send offprint requests to: T.C. Teixeira

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© European Southern Observatory (ESO) 1999

Online publication: November 2, 1999
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