J/ApJ/780/85 Molecular line study of infrared dark clouds (Vasyunina+, 2014)
Organic species in infrared dark clouds.
Vasyunina T., Vasyunin A.I., Herbst E., Linz H., Voronkov M., Britton T.,
Zinchenko I., Schuller F.
<Astrophys. J., 780, 85 (2014)>
=2014ApJ...780...85V 2014ApJ...780...85V
ADC_Keywords: Infrared sources ; Molecular clouds ; Interstellar medium ;
Millimetric/submm sources ; Radio lines ; Abundances
Keywords: ISM: clouds - ISM: molecules - radio lines: ISM - stars: formation
Abstract:
It is currently assumed that infrared dark clouds (IRDCs) represent
the earliest evolutionary stages of high-mass stars (>8M☉).
Submillimeter and millimeter-wave studies performed over the past 15yr
show that IRDCs possess a broad variety of properties, and hence a
wide range of problems and questions that can be tackled. In this
paper, we report an investigation of the molecular composition and
chemical processes in two groups of IRDCs. Using the Mopra, APEX, and
IRAM radio telescopes over the last four years, we have collected
molecular line data for CO, H2CO, HNCO, CH3CCH, CH3OH, CH3CHO,
CH3OCHO, and CH3OCH3. For all of these species we estimated
molecular abundances. We then undertook chemical modeling studies,
concentrating on the source IRDC028.34+0.06, and compared observed and
modeled abundances. This comparison showed that to reproduce observed
abundances of complex organic molecules, a zero-dimensional gas-grain
model with constant physical conditions is not sufficient. We achieved
greater success with the use of a warm-up model, in which warm-up from
10K to 30K occurs following a cold phase.
Description:
For the present study, two sets of InfraRed Dark Clouds (IRDCs) were
used, as listed in Tables 1 and 2. A set of southern sources, shown in
Table 1, was selected from Vasyunina et al. 2011 (cat. J/A+A/527/A88).
A set of northern sources, shown in Table 2, was taken from previous
studies and includes classical clouds from the first studies about
molecular line observations in IRDCs (e.g., Carey et al.,
1998ApJ...508..721C 1998ApJ...508..721C; Pillai et al., 2006A&A...450..569P 2006A&A...450..569P; Simon et al.
2006, cat. J/ApJ/639/227) as well as the recent work by Ragan et al.
2012 (cat. J/A+A/547/A49).
With 22m Mopra telescope, several observational setups were employed.
In all cases, we used the MOPS spectrometer, which allowed us to place
16 "zoom" windows along the 8.3GHz bandpass and reach a resolution of
0.1km/s, or 30kHz. Since for the present study we are interested
mainly in organic species, we will focus only on the CO, HNCO,
CH3CCH, and CH3OH molecules observed with Mopra. Four CO
isotopologues, 12CO, 13CO, C18O, C17O, and CH3OH lines, were
observed on 2011 April 27-May 2 with the central frequencies of
111.6GHz and 81GHz, respectively. The HNCO and CH3CCH data were
obtained by adopting a central frequency of 89.27GHz, and have been
already presented in Vasyunina et al. 2011 (cat. J/A+A/527/A88).
Observations with the Atacama Pathfinder Experiment (APEX) telescope
were conducted on 2011 September 25-26, 2011 November 15-18 and 2012
September 12-14. We used the APEX-1 receiver of the Swedish Heterodyne
Facility Instrument (SHeFI) with frequency settings at 218.75, 243.25,
and 214.77GHz. The backend for all observations was the eXtended
bandwidth Fast Fourier Transform Spectrometer (XFFTS) with
instantaneous bandwidth of 2.5GHz and 32768 spectral channels. This
allowed us to cover the intervals 213-220.5GHz, and 241.5-243GHz for
the southern objects and 213-220GHz for the northern objects with
88.5kHz spectral resolution. See Section 2.3 for all the details about
the APEX observations.
Observations with the IRAM 30m were performed on 2011 June 8-12. For
these observations, the EMIR receiver with the Fast Fourier Transform
Spectrometer (FTS) as a backend was used. During the observing run,
the frequency intervals 76-79GHz and 152.5-156.5GHz were covered with
a spectral resolution of 195kHz. According to the IRAM official
website, at 86GHz the beam size is 29'', and the beam efficiency is
0.81, while at 153GHz, the telescope beam size is 16'', and the beam
efficiency is 0.74.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 59 25 List of observed southern InfraRed Dark Clouds (IRDCs)
table2.dat 74 18 List of observed northern InfraRed Dark Clouds (IRDCs)
table6.dat 113 25 Abundances estimated for southern InfraRed Dark Clouds
table7.dat 164 18 Abundances estimated for northern InfraRed Dark Clouds
table8.dat 91 300 Line parameters for southern InfraRed Dark Clouds
table9.dat 91 252 Line parameters for northern InfraRed Dark Clouds
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See also:
J/ApJS/202/1 : 1mm spectral line survey toward GLIMPSE EGOs (He+, 2012)
J/ApJ/756/60 : A 3mm line survey in 37 IR dark clouds (Sanhueza+, 2012)
J/A+A/547/A49 : Herschel EPoS: high-mass overview (Ragan+, 2012)
J/A+A/527/A88 : Chemistry in infrared dark clouds (Vasyunina+, 2011)
J/ApJ/715/310 : Early stages of star formation in IRDCs (Rathborne+, 2010)
J/A+A/499/149 : 1.2mm maps of southern Infrared Dark Clouds (Vasyunina+, 2009)
J/A+A/505/405 : A catalogue of Spitzer dark clouds (Peretto+, 2009)
J/A+A/474/883 : ISOSS J23053+5953 maps (Birkmann+, 2007)
J/A+A/455/971 : Organic molecules in Galactic center (Requena-Torres+, 2006)
J/ApJ/641/389 : Millimetric observations of IRDC cores (Rathborne+, 2006)
J/ApJ/639/227 : MSX IRDC candidate catalog (Simon+, 2006)
J/ApJS/166/567 : Radio Molecular lines in infrared dark clouds (Ragan+, 2006)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 12 A12 --- Name Identifier of the InfraRed Dark Cloud (IRDC)
14- 15 I2 h RAh Hour of Right Ascension (J2000)
17- 18 I2 min RAm Minute of Right Ascension (J2000)
20- 25 F6.3 s RAs Second of Right Ascension (J2000)
27 A1 --- DE- Sign of the Declination (J2000)
28- 29 I2 deg DEd Degree of Declination (J2000)
31- 32 I2 arcmin DEm Arcminute of Declination (J2000)
34- 38 F5.2 arcsec DEs Arcsecond of Declination (J2000)
40- 42 F3.1 kpc Dist [2.1/5.3] Distance (1)
44 A1 --- n_Dist [c] "c" denotes a distance from Saito et al.
(2001PASJ...53.1037S 2001PASJ...53.1037S)
46- 49 F4.1 K Tkin [11/49] Kinetic temperature (1)
51- 53 F3.1 10+22cm-2 NH2 [0.3/5.2] H2 column density (1)
55- 59 A5 --- Class Mid-infrared category (A, M, Q, SiO) (G1)
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Note (1): Taken from Vasyunina et al. 2011 (cat. J/A+A/527/A88).
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Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
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1- 12 A12 --- Name Identifier of the infrared dark cloud (IRDC)
14- 15 I2 h RAh Hour of Right Ascenion (J2000)
17- 18 I2 min RAm Minute of Right Ascension (J2000)
20- 24 F5.2 s RAs Second of Right Ascension (J2000)
26 A1 --- DE- Sign of the Declination (J2000)
27- 28 I2 deg DEd Degree of Declination (J2000)
30- 31 I2 arcmin DEm Arcminute of Declination (J2000)
33- 36 F4.1 arcsec DEs Arcsecond of Declination (J2000)
38- 41 F4.2 kpc Dist [1/4.8] Distance
43- 46 F4.2 kpc Dist2 ? Second value for distance
48- 49 I2 K Tkin [13/16]? Kinetic distance (1)
51- 52 I2 K Tdust [17/33]? Dust temperature
54- 57 F4.1 10+22cm-2 NH2 [1.1/14.2] H2 column density (2)
59 A1 --- r_NH2 [ab] Source of NH2 (3)
61- 66 A6 --- Class Mid-infrared category (A, M, Q, SiO) (G1)
68- 74 A7 --- Ref Reference (4)
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Note (1): Kinetic temperature estimated based on ammonia measurement and dust
temperature.
Note (2): H2 column density calculated adopting 29'' beam size and ammonia
kinetic temperature.
Note (3): Reference codes are defined as follows:
a = H2 column density adopted from Pillai et al. (2006A&A...450..569P 2006A&A...450..569P);
b = H2 column density calculated based on SCUBA 850µm flux estimate from
Birkmann et al. 2007 (cat. J/A+A/474/883).
Note (4): Reference codes are defined as follows:
1 = Wienen et al. 2012 (cat. J/A+A/544/A146);
2 = Pillai et al. (2006A&A...450..569P 2006A&A...450..569P);
3 = Carey et al. (1998ApJ...508..721C 1998ApJ...508..721C);
4 = Vasyunina et al. 2011 (cat. J/A+A/527/A88);
5 = Rathborne et al. 2006 (cat. J/ApJ/641/389);
6 = Sanhueza et al. 2012 (cat. J/ApJ/756/60);
7 = Sakai et al. (2008ApJ...678.1049S 2008ApJ...678.1049S);
8 = Sridharan et al. (2002ApJ...566..931S 2002ApJ...566..931S);
9 = Ragan et al. 2012 (cat. J/A+A/547/A49);
10 = Pitann et al. (2013ApJ...766...68P 2013ApJ...766...68P);
11 = Birkmann et al. 2007 (cat. J/A+A/474/883);
12 = Wouterloot et al. (1988A&A...203..367W 1988A&A...203..367W).
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Byte-by-byte Description of file: table6.dat
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Bytes Format Units Label Explanations
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1- 12 A12 --- Name Identifier of the InfraRed Dark Cloud (IRDC)
14- 25 A12 --- COa CO abundance (a(b)=a*10b) (G2)
27- 29 A3 --- f_COb [n/a] 'n/a' indicates absence of CO abundance
31- 42 A12 --- COb CO abundance (a(b)=a*10b) (2)
44- 55 A12 --- HNCO HNCO abundance (a(b)=a*10b) (3)
57- 69 A13 --- H2CO H2CO abundance (a(b)=a*10b) (4)
71- 83 A13 --- CH3OH CH3OH abundance (a(b)=a*10b) (5)
85 A1 --- f_CH3OH [g] 'g' indicates abundance calculated based
on CH3OH 51,541,4 E transition
87- 90 F4.1 K Tex1 [12/53]? CH3OH excitation temperature
92-104 A13 --- CH3CCH CH3CCH abundance (a(b)=a*10b) (6)
106-107 I2 K Tex2 [17/38]? CH3CCH excitation temperature
109-113 A5 --- Class Mid-infrared category (A, M, Q, SiO) (G1)
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Note (2): CO abundance estimated based on C18O(1-0) Mopra data. Blank space
indicates non-detection. CO shows a detection rate of 100%.
Note (3): HNCO data taken from Vasyunina et al. 2011 (cat. J/A+A/527/A88). Blank
space indicates non-detection. HNCO shows a detection rate of 40%.
Note (4): H2CO abundance estimated based on H2CO(30,3-20,2) APEX data.
Blank space indicates non-detection. H2CO shows a detection rate of 60%.
Note (5): CH3OH abundance estimated based on APEX data. Blank space indicates
non-detection. CH3OH shows a detection rate of 48%.
Note (6): Blank space indicates non-detection. CH3CCH shows a detection rate
of 20%.
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Byte-by-byte Description of file: table7.dat
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Bytes Format Units Label Explanations
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1- 12 A12 --- Name Identifier of the InfraRed Dark Cloud (IRDC)
14- 16 A3 --- f_CO [n/a] 'n/a' indicates absence of CO abundance
18- 29 A12 --- CO CO abundance (a(b)=a*10b) (G2)
31- 43 A13 --- HNCO HNCO abundance (a(b)=a*10b) (1)
45- 47 A3 --- f_H2CO [n/a] 'n/a' indicates absence of H2CO abundance
49- 62 A14 --- H2CO H2CO abundance (a(b)=a*10b) (2)
64- 75 A12 --- CH3OH CH3OH abundance (a(b)=a*10b) (3)
77- 84 A8 --- e_CH3OH Uncertainty in CH3OH (a(b)=a*10b)
86 A1 --- f_CH3OH [cde] Estimate source of CH3OH (4)
88- 89 I2 K Tex1 [25/43]? CH3OH excitation temperature
91 I1 K e_Tex1 ? Uncertainty in Tex1
93-104 A12 --- CH3CCH CH3CCH abundance (a(b)=a*10b) (5)
106-113 A8 --- e_CH3CCH Uncertainty in CH3CCH (a(b)=a*10b)
115-116 I2 K Tex2 [27/42]? CH3CCH excitation temperature
118-119 I2 K e_Tex2 [1/13]? Uncertainty in Tex2
121-133 A13 --- CH3CHO CH3CHO abundance (a(b)=a*10b) (6)
135-142 A8 --- e_CH3CHO Uncertainty in CH3CHO
144-145 I2 K Tex3 [23]? CH3CHO excitation temperature
147 I1 K e_Tex3 ? Uncertainty in Tex3
149 A1 --- l_CH3OCH3 [<] Upper limit flag in CH3OCH3
150-157 A8 --- CH3OCH3 CH3OCH3 abundance (a(b)=a*10b) (7)
159-164 A6 --- Class Mid-infrared category (A, M, Q, SiO) (G1)
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Note (1): Blank space indicates non-detection. HNCO shows a detection rate of
89%.
Note (2): H2CO abundance estimated based on H2CO(30,3-20,2) APEX data.
Blank space indicates non-detection. H2CO shows a detection rate of 100%.
Note (3): Blank space indicates non-detection. CH3OH shows a detection rate of
33%.
Note (4): Source of CH3OH abundance estimate defined as follows:
c = CH3OH abundance estimated based on He et al. 2012 (cat. J/ApJS/202/1)
data and APEX data from the current survey;
d = CH3OH abundance estimated based on APEX and IRAM data;
e = Abundance calculated based on CH3OH 42,2-31,2E transition.
Note (5): Blank space indicates non-detection. CH3CCH shows a detection rate
of 89%.
Note (6): Blank space indicates non-detection. CH3CHO shows a detection rate
of 61%.
Note (7): Blank space indicates non-detection. CH3OCH3 shows a detection
rate of 28%.
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Byte-by-byte Description of file: table[89].dat
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Bytes Format Units Label Explanations
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1- 8 A8 --- Mol Molecule identifier
10- 26 A17 --- Trans Transition
28- 39 A12 --- Name Identifier of the InfraRed Dark Cloud (IRDC)
41- 46 F6.3 K.km/s TAint [0.02/25]? Integrated antenna temperature
(∫TAdv) (1)
48 A1 --- f_TAint [n] Indicates an absence of data
50- 53 F4.2 K.km/s e_TAint [0/0.4]? Uncertainty in TAint (1)
55- 61 F7.3 km/s Vlsr [-61/80]? Local standard of rest velocity
(Vlsr) (1)
63- 66 F4.2 km/s e_Vlsr [0/2]? Uncertainty in Vlsr (1)
68- 72 F5.3 km/s DelV [0.4/6.7]? Line width (ΔV) (1)
74- 78 F5.3 km/s e_DelV [0/2.83]? Uncertainty in DelV (1)
80- 85 F6.4 K TA [0.01/8.1]? Antenna temperature (TA) (1)
87- 91 F5.3 K rms [0.01/0.12]? The 1σ rms (1)
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Note (1): A blank value indicates a non-detection.
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Note (G1): Category is determined according to mid-infrared classification
defined as follows:
A = "Active" core (source that appears in emission at both 8 and 24µm);
M = "Middle" (where only 24µm emission appears);
Q = "Quiescent" (source that shows no emission at 8 and 24µm);
SiO = Detected SiO emission (as an indicator of star formation activity) as
described in Vasyunina et al. 2011 (cat. J/A+A/527/A88) and H. Linz et
al. (in preparation; see the text in Section 2.1).
Note (G2): CO abundance estimated based on C18O(2-1) APEX data. Blank space
indicates non-detection. CO shows a detection rate of 100%.
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History:
From electronic version of the journal
(End) Greg Schwarz [AAS], Sylvain Guehenneux [CDS] 29-Jan-2015