2010A&A...518A..52A


C.D.S. - SIMBAD4 rel 1.7 - 2021.03.03CET01:44:24

2010A&A...518A..52A - Astronomy and Astrophysics, volume 518, A52-52 (2010/7-2)

Chemical study of intermediate-mass (IM) class 0 protostars. CO depletion and N2H+ deuteration.

ALONSO-ALBI T., FUENTE A., CRIMIER N., CASELLI P., CECCARELLI C., JOHNSTONE D., PLANESAS P., RIZZO J.R., WYROWSKI F., TAFALLA M., LEFLOCH B., MARET S. and DOMINIK C.

Abstract (from CDS):

We are carrying out a physical and chemical study of the protostellar envelopes in a representative sample of IM Class 0 protostars. In our first paper we determined the physical structure (density-temperature radial profiles) of the protostellar envelopes. Here, we study the CO depletion and N2H+ deuteration. We observed the millimeter lines of C18O, C17O, N2H+ and N2D+ towards the protostars using the IRAM 30m telescope. Based on these observations, we derived the C18O, N2H+ and N2D+ radial abundance profiles across their envelopes using a radiative transfer code. In addition, we modeled the chemistry of the protostellar envelopes. All the C18O 1->0 maps are well fit when assuming that the C18O abundance decreases inwards within the protostellar envelope until the gas and dust reach the CO evaporation temperature, ≃20-25K, where the CO is released back to the gas phase. The N2H+ deuterium fractionation in Class 0 IMs is [N2D+]/[N2H+]=0.005-0.014, two orders of magnitude higher than the elemental [D/H] value in the interstellar medium, but a factor of 10 lower than in prestellar clumps. Chemical models account for the C18O and N2H+ observations if we assume the CO abundance is a factor of ∼2 lower than the canonical value in the inner envelope. This could be the consequence of the CO being converted into CH3OH on the grain surfaces prior to the evaporation and/or the photodissociation of CO by the stellar UV radiation. The deuterium fractionation is not fitted by chemical models. This discrepancy is very likely caused by the simplicity of our model that assumes spherical geometry and neglects important phenomena like the effect of bipolar outflows and UV radiation from the star. More important, the deuterium fractionation is dependent on the ortho-to-para H2 ratio, which is not likely to reach the steady-state value in the dynamical time scales of these protostars.

Abstract Copyright:

Journal keyword(s): ISM: abundances - ISM: clouds - stars: formation - circumstellar matter

Simbad objects: 21

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Number of rows : 21

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 LBN 119.83-06.05 MoC 00 28 43.5075 +56 41 56.868           ~ 65 0
2 LDN 1544 DNe 05 04 16.6 +25 10 48           ~ 716 0
3 NAME [BM89] L1544 cor 05 04 22.5 +25 11 36           ~ 435 1
4 V* V2457 Ori Or* 05 35 26.97000 -05 09 54.4644         18.858 ~ 120 0
5 [SMZ2000] L1643-S3 MMS 1 smm 05 39 55.9 -07 30 28           ~ 13 0
6 NAME Serpens Cloud SFR 18 29 49 +01 14.8           ~ 958 2
7 NAME SH 2-68 FIR 1 cor 18 29 49.63 +01 15 21.9           ~ 241 2
8 IC 1396 OpC 21 39 00 +57 29.4           ~ 449 1
9 [BGE2002] BIMA 1 Y*O 21 40 39.67 +58 16 06.2           ~ 15 0
10 [BGE2002] BIMA 2 Y*O 21 40 42.36 +58 16 09.7           ~ 116 0
11 NAME IC 1396 North CGb 21 40 42.6537 +58 16 01.882           ~ 182 1
12 [BGE2002] BIMA 3 Y*O 21 40 42.77 +58 16 01.1           ~ 16 0
13 NGC 7129 OpC 21 42 56 +66 06.2     11.5     ~ 236 0
14 EM* LkHA 234 Ae* 21 43 06.8214472757 +66 06 54.199354231 13.65 13.61 12.73 11.98 11.20 B5Ve 278 0
15 NAME NGC 7129 FIR 2 IR 21 44 01.5 +66 03 40           ~ 86 0
16 SH 2-140 OpC 22 19 07.8 +63 17 07           ~ 636 2
17 IRAS 22176+6303 Y*O 22 19 17.978 +63 18 52.92           ~ 590 0
18 NAME SH 2-140 IRS 1 Y*O 22 19 18.277 +63 18 45.82           ~ 192 0
19 NAME SH 2-140 IRS 2 IR 22 19 18.514 +63 18 55.16           ~ 35 0
20 NAME SH 2-140 IRS 3 IR 22 19 19.853 +63 18 48.07           ~ 47 0
21 NAME Cep E HII 23 03 12.779 +61 42 25.75           ~ 157 0

    Equat.    Gal    SGal    Ecl

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2021.03.03-01:44:24

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