2010A&A...513A..41H


C.D.S. - SIMBAD4 rel 1.7 - 2020.07.14CEST22:50:12

2010A&A...513A..41H - Astronomy and Astrophysics, volume 513, A41-41 (2010/4-1)

Nitrogen chemistry and depletion in starless cores.

HILY-BLANT P., WALMSLEY M., PINEAU DES FORETS G. and FLOWER D.

Abstract (from CDS):

We investigated the chemistry of nitrogen-containing species, principally isotopologues of CN, HCN, and HNC, in a sample of pre-protostellar cores. We used the IRAM 30m telescope to measure the emission in rotational and hyperfine transitions of CN, HCN, 13CN, H13CN, HN13C, and HC13N in L 1544, L 183, Oph D, L 1517B, L 310. The observations were made along axial cuts through the dust emission peak, at a number of regularly-spaced offset positions. The observations were reduced and analyzed to obtain the column densities, using the measurements of the less abundant isotopic variants in order to minimize the consequences of finite optical depths in the lines. The observations were compared with the predictions of a free-fall gravitational collapse model, which incorporates a non-equilibrium treatment of the relevant chemistry. We found that CN, HCN, and HNC remain present in the gas phase at densities well above that at which CO depletes on to grains. The CN:HCN and the HNC:HCN abundance ratios are larger than unity in all the objects of our sample. Furthermore, there is no observational evidence for large variations of these ratios with increasing offset from the dust emission peak and hence with density. Whilst the differential freeze-out of CN and CO can be understood in terms of the current chemistry, the behaviour of the CN:HCN ratio is more difficult to explain. Models suggest that most nitrogen is not in the gas phase but may be locked in ices. Unambiguous conclusions require measurements of the rate coefficients of the key neutral-neutral reactions at low temperatures.

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Journal keyword(s): ISM: abundances - ISM: molecules - ISM: clouds

Simbad objects: 8

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Number of rows : 8

N Identifier Otype ICRS (J2000)
RA
ICRS (J2000)
DEC
Mag U Mag B Mag V Mag R Mag I Sp type #ref
1850 - 2020
#notes
1 TMC-1 MoC 04 41 45.9 +25 41 27           ~ 1359 0
2 NAME [BM89] L1517B cor 04 55 18.8 +30 38 04           ~ 130 0
3 LDN 1544 DNe 05 04 16.6 +25 10 48           ~ 681 0
4 NAME [BM89] L1544 cor 05 04 22.5 +25 11 36           ~ 434 1
5 LDN 183 MoC 15 54 12.2 -02 49 42           ~ 682 1
6 NAME Ophiuchus D MoC 16 28 29.2 -24 18 25           ~ 103 0
7 LDN 57 DNe 17 22 38.2 -23 49 34           ~ 283 1
8 LDN 310 DNe 18 07 12 -18 21.6           ~ 10 0

    Equat.    Gal    SGal    Ecl

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2020.07.14-22:50:12

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