2011A&A...529A.112W


Query : 2011A&A...529A.112W

2011A&A...529A.112W - Astronomy and Astrophysics, volume 529A, 112-112 (2011/5-1)

Sulfur chemistry: 1D modeling in massive dense cores.

WAKELAM V., HERSANT F. and HERPIN F.

Abstract (from CDS):

The main sulfur-bearing molecules OCS, H2S, SO, SO2, and CS have been observed in four high mass dense cores (W43-MM1, IRAS 18264, IRAS 05358, and IRAS 18162). Our goal is to put some constraints on the relative evolutionary stage of these sources by comparing these observations with time-dependent chemical modeling. We used the chemical model Nahoon, which computes the gas-phase chemistry and gas-grain interactions of depletion and evaporation. Mixing of the different chemical compositions shells in a 1D structure through protostellar envelope has been included since observed lines suggest nonthermal supersonic broadening. Observed radial profiles of the temperature and density are used to compute the chemistry as a function of time. With our model, we underproduce CS by several orders of magnitude compared to the other S-bearing molecules, which seems to contradict observations, although some uncertainties in the CS abundance observed at high temperature remain. The OCS/SO2, SO/SO2, and H2S/SO2 abundance ratios could in theory be used to trace the age of these massive protostars since they show a strong dependence with time, but the sources are too close in age compared to the accuracy of chemical models and observations. Our comparison between observations and modeling may, however, indicate that W43-MM1 could be chemically younger than the three other sources. Turbulent diffusivity through the protostellar envelopes has to be less efficient than 2x1014 cm2/s. Otherwise, it would have smoothed out the abundance profiles, and this would have been observed. The sulfur chemistry depends strongly on the 1D physical conditions. Any observed set of abundances should be compared with a chemical model computed with the same temperature and density traced by the observations. In our case, no conclusion can be given on the relative age of IRAS 18264, IRAS 18162 and IRAS 05358 except that they are very close. W43-MM1 seems younger than the other sources. Turbulent mixing could occur in young high-mass protostars on a geometric scale that is too small to affect the chemical abundance profiles through the envelope.

Abstract Copyright:

Journal keyword(s): astrochemistry - turbulence - stars: formation - ISM: molecules

Simbad objects: 9

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Number of rows : 9
N Identifier Otype ICRS (J2000)
RA
ICRS (J2000)
DEC
Mag U Mag B Mag V Mag R Mag I Sp type #ref
1850 - 2021
#notes
1 NAME Orion-KL SFR 05 35 14.16 -05 22 21.5           ~ 2091 1
2 IRAS 05358+3543 mul 05 39 10.4 +35 45 19           ~ 139 1
3 LDN 183 MoC 15 54 12.2 -02 49 42           ~ 707 1
4 IRAS 16293-2422 cor 16 32 22.56 -24 28 31.8           ~ 1104 1
5 SNR G012.8-00.2 SFR 18 14 14.0 -17 55 50           ~ 228 0
6 NAME HH 80-81 IRS HII 18 19 11.8 -20 47 35           ~ 137 0
7 IRAS 18264-1152 cor 18 29 14.6846 -11 50 23.966           ~ 74 1
8 AGAL G030.818-00.056 cor 18 47 47.0 -01 54 28           ~ 123 0
9 RAFGL 2591 Y*O 20 29 25.03656 +40 11 20.3316           ~ 578 0

    Equat.    Gal    SGal    Ecl

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2021.07.29-18:14:24

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