2018A&A...615A..88B


Query : 2018A&A...615A..88B

2018A&A...615A..88B - Astronomy and Astrophysics, volume 615A, 88-88 (2018/7-1)

Low levels of methanol deuteration in the high-mass star-forming region NGC 6334I.

BOGELUND E.G., McGUIRE B.A., LIGTERINK N.F.W., TAQUET V., BROGAN C.L., HUNTER T.R., PEARSON J.C., HOGERHEIJDE M.R. and VAN DISHOECK E.F.

Abstract (from CDS):


Context. The abundance of deuterated molecules in a star-forming region is sensitive to the environment in which they are formed. Deuteration fractions, in other words the ratio of a species containing D to its hydrogenated counterpart, therefore provide a powerful tool for studying the physical and chemical evolution of a star-forming system. While local low-mass star-forming regions show very high deuteration ratios, much lower fractions are observed towards Orion and the Galactic centre. Astration of deuterium has been suggested as a possible cause for low deuteration in the Galactic centre.
Aims. We derive methanol deuteration fractions at a number of locations towards the high-mass star-forming region NGC 6334I, located at a mean distance of 1.3kpc, and discuss how these can shed light on the conditions prevailing during its formation.
Methods. We use high sensitivity, high spatial and spectral resolution observations obtained with the Atacama Large Millimeter/submillimeter Array to study transitions of the less abundant, optically thin, methanol-isotopologues: 13CH3OH, CH318OH, CH2DOH and CH3OD, detected towards NGC 6334I. Assuming local thermodynamic equilibrium (LTE) and excitation temperatures of ∼120-330K, we derive column densities for each of the species and use these to infer CH2DOH/CH3OH and CH3OD/CH3OH fractions.
Results. We derive column densities in a range of (0.8-8.3)x1017cm–2 for 13CH3OH, (0.13-3.4)x1017cm–2 for CH318OH, (0.03-1.63)x1017cm–2 for CH2DOH and (0.15-5.5)x1017cm–2 for CH3OD in a ∼1'' beam. Interestingly, the column densities of CH3OD are consistently higher than those of CH2DOH throughout the region by factors of 2-15. We calculate the CH2DOH to CH3OH and CH3OD to CH3OH ratios for each of the sampled locations in NGC 6334I. These values range from 0.03% to 0.34% for CH2DOH and from 0.27% to 1.07% for CH3OD if we use the 13C isotope of methanol as a standard; using the 18 O-methanol as a standard, decreases the ratios by factors of between two and three.
Conclusions. All regions studied in this work show CH2DOH/CH3OH as well as CH2DOH/CH3OD values that are considerably lower than those derived towards low-mass star-forming regions and slightly lower than those derived for the high-mass star-forming regions in Orion and the Galactic centre. The low ratios indicate a grain surface temperature during formation ∼30K, for which the efficiency of the formation of deuterated species is significantly reduced. Therefore, astration of deuterium in the Galactic centre cannot be the explanation for its low deuteration ratio but rather the high temperatures characterising the region.

Abstract Copyright: © ESO 2018

Journal keyword(s): astrochemistry - methods: observational - stars: protostars - ISM: individual objects: NGC 6334I - submillimeter: ISM

Simbad objects: 25

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Number of rows : 25
N Identifier Otype ICRS (J2000)
RA
ICRS (J2000)
DEC
Mag U Mag B Mag V Mag R Mag I Sp type #ref
1850 - 2023
#notes
1 NAME Perseus Cloud SFR 03 35.0 +31 13           ~ 1250 0
2 NAME Orion-KL SFR 05 35 14.16 -05 22 21.5           ~ 2192 1
3 NAME Ori Region reg 05 35 17.30 -05 23 28.0           ~ 545 0
4 NAME Ori Complex Cld 05 35.3 -05 23           ~ 404 0
5 NAME Ori B MoC 05 41 43.0 -01 54 44           ~ 1291 0
6 HH 212 HH 05 43 51.41 -01 02 53.1           ~ 350 1
7 IRAS 16293-2422 cor 16 32 22.56 -24 28 31.8           ~ 1183 1
8 NGC 6334E HII 17 20 50.9 -35 46 06           ~ 51 0
9 [BHC2016] CM1 Rad 17 20 51.856 -35 47 04.48           ~ 4 0
10 NGC 6334 HII 17 20 53 -36 07.9           ~ 647 0
11 [BHC2016] MM5 mm 17 20 53.040 -35 47 09.93           ~ 3 0
12 [BHC2016] MM6 mm 17 20 53.122 -35 47 02.80           ~ 2 0
13 [BHC2016] MM2 mm 17 20 53.188 -35 46 59.32           ~ 32 0
14 NAME NGC 6334-I Cl* 17 20 53.35 -35 47 01.5           ~ 316 0
15 [BHC2016] CM2 Rad 17 20 53.384 -35 46 55.68           ~ 8 0
16 [BHC2016] MM1 mm 17 20 53.415 -35 46 57.88           ~ 71 0
17 NAME NGC 6334F (C) HII 17 20 53.45 -35 47 02.6           ~ 220 1
18 [BHC2016] MM7 mm 17 20 53.641 -35 46 54.83           ~ 4 0
19 [BHC2016] MM8 mm 17 20 53.703 -35 47 06.07           ~ 2 0
20 [BHC2016] MM9 mm 17 20 53.896 -35 46 59.10           ~ 3 0
21 NAME NGC 6334 I(N) smm 17 20 54 -35 45.0           ~ 141 1
22 NAME Galactic Center reg 17 45 39.60213 -29 00 22.0000           ~ 13323 0
23 [QSR2011] Sgr B2(N)-SMA2 cor 17 47 19.885 -28 22 13.29           ~ 70 0
24 [DMN2000] Sgr B2 N2 PoC 17 47 19.90 -28 23 17.3           ~ 14 0
25 NAME Sgr B2 MoC 17 47 20.4 -28 23 07           ~ 2134 1

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2022.12.02-15:18:28

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