2012A&A...540A.104M


C.D.S. - SIMBAD4 rel 1.7 - 2021.04.16CEST13:33:06

2012A&A...540A.104M - Astronomy and Astrophysics, volume 540A, 104-104 (2012/4-1)

A molecular line study of the filamentary infrared dark cloud G304.74+01.32.

MIETTINEN O.

Abstract (from CDS):

Infrared dark clouds (IRDCs) are promising sites to study the earliest formation stages of stellar clusters and high-mass stars, and the physics of molecular-cloud formation and fragmentation. We attempt to improve our understanding of the physical and chemical properties of the filamentary IRDC G304.74+01.32 (hereafter, G304.74). In particular, we investigate the kinematical and dynamical state of the cloud and clumps within it, and the amount of CO depletion. All of the submillimetre peak positions in the cloud identified from our previous LABOCA 870-µm map were observed in C17O(2-1) with APEX. These are the first line observations along the whole filament that have been made so far. Selected positions were also observed in the 13CO(2-1), SiO(5-4), and CH3OH(5k-4k) transitions at ∼1mm. The C17O lines were detected towards all target positions at similar radial velocities. CO does not appear to be significantly depleted in the clumps, the largest depletion factors being only about 2. Two to three methanol 5k-4k lines near ∼241.8 GHz were detected towards all selected positions, whereas SiO(5-4) was seen in only one of these positions, namely SMM 3. In the band covering SiO(5-4), we also detected the DCN(3-2) line towards SMM 3. The 13CO(2-1) lines display blue asymmetric profiles, which are indicative of large-scale infall motions. The clumps show transonic to supersonic non-thermal motions, and a virial-parameter analysis suggests that most of them are gravitationally bound. The external pressure may also play a non-negligible role in the dynamics. Our analysis suggests that the fragmentation of the filament into clumps is caused by a ``sausage''-type instability, in agreement with results from other IRDCs. The uniform C17O radial velocities along the G304.74 cloud shows that it is a coherent filamentary structure. Although the clumps appear to be gravitationally bound, the ambient turbulent ram pressure may be an important factor in the cloud dynamics. This is qualitatively consistent with our earlier suggestion that the filament was formed by converging supersonic turbulent flows. The poloidal magnetic field could resist the radial cloud collapse, which conforms to the low infall velocites that we derived. The cloud may be unable to form high-mass stars based on the mass-size threshold. The star-formation activity in the cloud, such as outflows, is likely responsible for the release of CO from the icy grain mantles back into the gas phase. Shocks related to outflows may also have injected CH3OH, SiO, and DCN into the gas-phase in SMM 3.

Abstract Copyright:

Journal keyword(s): ISM: abundances - ISM: molecules - ISM: clouds - stars: formation - ISM: individual objects: G304.74+01.32 - lines: ISM radio

Simbad objects: 27

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Number of rows : 27

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 [BM89] L1498 PoC 04 10 51.4 +25 09 58           ~ 187 0
2 LDN 1498 DNe 04 11.0 +24 58           ~ 255 0
3 NAME [BM89] L1517B cor 04 55 18.8 +30 38 04           ~ 133 0
4 NAME Orion-KL SFR 05 35 14.16 -05 22 21.5           ~ 2064 1
5 M 42 HII 05 35 17.3 -05 23 28           ~ 3787 0
6 NAME Polaris Flare MoC 11 00 14.8 +86 10 52           ~ 168 1
7 NAME Coalsack Nebula DNe 12 31 19 -63 44.6           ~ 246 0
8 [MH2010] SMM1 MoC 13 06 20.5 -61 30 15           ~ 5 0
9 [MH2010] SMM2 MoC 13 06 26.9 -61 29 39           ~ 5 0
10 [BBC2006] IRAS 13039-6108 Clump 1 cor 13 06 35.8 -61 28 53           ~ 5 0
11 MSXDC G304.74+1.32 DNe 13 06.6 -61 30           ~ 9 0
12 [BBC2006] IRAS 13039-6108 Clump 3 cor 13 06 44.7 -61 28 35           ~ 5 0
13 [MH2010] SMM5 MoC 13 06 49.9 -61 26 55           ~ 5 0
14 IRAS 13037-6112 HII 13 06 51.0 -61 28 22           ~ 7 0
15 [BBC2006] IRAS 13039-6108 Clump 4 cor 13 06 51.1 -61 27 49           ~ 5 0
16 [BBC2006] IRAS 13039-6108 Clump 8 cor 13 07 02.6 -61 26 18           ~ 5 0
17 IRAS 13039-6108 MIR 13 07 06.4 -61 24 29           ~ 10 0
18 [MH2010] SMM8 MoC 13 07 08.9 -61 22 49           ~ 5 0
19 [BBC2006] IRAS 13039-6108 Clump 6 cor 13 07 12.7 -61 22 49           ~ 7 0
20 IRAS 13042-6105 MIR 13 07 20.3 -61 21 45           ~ 5 0
21 NAME the Pipe Nebula DNe 17 30 -25.0           ~ 351 1
22 MMB G011.109-00.114 Y*O 18 10 28.4449 -19 22 38.782           ~ 47 0
23 [CCE98b] 011.11-0.12 Cld 18 10.5 -19 23           ~ 87 1
24 NAME Aql Rift DNe 18 32 -01.0           ~ 263 1
25 ISOSS J18364-0221 IR 18 36.4 -02 21           ~ 8 0
26 MSXDC G035.39-0.33 MoC 18 57 09.0 +02 07 46           ~ 95 0
27 MSXDC G049.40-0.01 Cld 19 22 13 +14 36.8           ~ 4 0

    Equat.    Gal    SGal    Ecl

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2021.04.16-13:33:06

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