J/ApJS/252/1 OH and HI data in molecular clouds (Tang+, 2021)
OH evolution in molecular clouds.
Tang N., Li Di, Yue N., Zuo P., Liu T., Luo G., Chen L., Qin S.-L., Wu Y.,
Heiles C.
<Astrophys. J. Suppl. Ser., 252, 1 (2021)>
=2021ApJS..252....1T 2021ApJS..252....1T
ADC_Keywords: Molecular clouds; H I data; Molecular data
Keywords: Hydroxyl sources ; Molecular gas ; Diffuse molecular clouds
Abstract:
We have conducted a OH 18cm survey toward 141 molecular clouds in
various environments, including 33 optical dark clouds, 98 Planck
Galactic cold clumps (PGCCs), and 10 Spitzer dark clouds with the
Arecibo telescope. The deviations from local thermal equilibrium are
common for intensity ratios of both OH main lines and satellite lines.
Line intensity of OH 1667MHz is found to correlate linearly with
visual extinction AV when AV is less than 3mag. It was converted
into OH column density by adopting the excitation temperature derived
from Monte Carlo simulations with 1σ uncertainty. The
relationship between OH abundance X(OH) relative to H2 and
AV is found to follow an empirical formula,
X(OH)/10-7=1.3-0.4+0.4+6.3-0.5+0.5*exp(-AV/2.9-0.6+0.6).
Linear correlation is found between OH and 13CO intensity. Besides,
nonthermal velocity dispersions of OH and 13CO are closely
correlated. These results imply tight chemical evolution and spatial
occupation between OH and 13CO. No obvious correlation is found
between column density and nonthermal velocity dispersion of OH and HI
narrow self-absorption (HINSA), indicating different chemical
evolution and spatial volume occupation between OH and HINSA. Using
the age information of HINSA analysis, OH abundance X(OH) is found to
increase linearly with cloud age, which is consistent with previous
simulations. Fourteen OH components without corresponding CO emission
were detected, implying the effectiveness of OH in tracing the
"CO-dark" molecular gas.
Description:
Observations of the OH 18cm transitions were carried out with the
Arecibo 300m telescope, whose beam size is 3.5' at 1.6GHz.
ODC (optical dark clouds from Dutra & Bica, 2002, J/A+A/383/631):
Three transitions of OH, 1612.2310, 1665.4018, and 1667.3590MHz, were
obtained during 2018 September and October.
PGCC (Planck Galactic cold clump from Planck+, 2016, J/A+A/594/A28).
Four transitions of OH, 1612.2310, 1665.4018, 1667.3590, and
1720.5300MHz, were obtained between 2013 November and 2015 November.
SDC (Spitzer dark cloud from Peretto & Fuller, 2009, J/A+A/505/405).
The observations were taken in 2013 November with same settings as for
PGCCs. See Section 2.2.
12CO(1-0) and its isotopes (13CO(1-0) and C18O(1-0))
observations toward 33 ODCs, 11 PGCCs, and 10 SDCs were made with
Delingha 13.7m during 2020 May and June. CO data of the rest of the 87
PGCCs were obtained from a CO survey with Delingha 13.7m in 2011
(Wu+ 2012, J/ApJ/756/76). See Section 2.3.
HI spectra toward ODCs were obtained simultaneously with the OH data.
HI data for the rest of the sources were extracted from the Galactic
Arecibo L-band Feed Array HI (GALFA-HI; Peek+ 2018, J/ApJS/234/2).
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table2.dat 152 193 Gaussian fitting parameters of OH data
table3.dat 87 70 Gaussian fitting parameters of HI narrow
self-absorption (HINSA) data
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See also:
J/A+A/383/631 : Catalogue of dust clouds in the Galaxy (Dutra+, 2002)
J/A+A/414/235 : OH maser emission from star forming regions (Szymczak+, 2004)
J/A+A/505/405 : A catalogue of Spitzer dark clouds (Peretto+, 2009)
J/ApJ/756/76 : Planck cold dust clumps CO survey (Wu+, 2012)
J/ApJS/209/37 : Planck cold clumps in 12CO, 13CO and C18O (Meng+, 2013)
J/A+A/580/A112 : THOR. The HI, OH, Recombination Line Survey (Bihr+, 2015)
J/A+A/590/A72 : Herschel counterparts of SDC (Peretto+, 2016)
J/A+A/594/A28 : Planck Catalogue of Galactic cold clumps (PGCC) (Planck+, 2016)
J/ApJS/224/43 : Planck cold clumps and cores in the 2nd quadrant (Zhang+, 2016)
J/ApJS/234/2 : The GALFA-HI survey data release 2 (Peek+, 2018)
J/ApJ/883/158 : Dark molecular gas in the Galaxy II. Perseus arm (Busch+, 2019)
Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
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1- 3 I3 --- Seq [1/141] Source index identifier
5 I1 --- m_Seq [0/4] Component number
7- 22 A16 --- Name Common identifier
24- 30 F7.3 deg GLON [33.10/201.85] Galactic longitude
32- 38 F7.3 deg GLAT [-24.9/11.4] Galactic latitude
40- 44 F5.2 K Tp1665 [-1.5/2.6]? OH 1665MHz line peak temperature
46- 49 F4.2 K e_Tp1665 [0.01/1.1]? Uncertainty in Tp1665
51- 56 F6.2 km/s Vc1665 [-20.5/110.2]? OH 1665MHz line center
velocity
58- 61 F4.2 km/s e_Vc1665 [0.01/1.1]? Uncertainty in Vc1665
63- 66 F4.2 km/s DV1665 [0.2/9.1]? OH 1665MHz line width
68- 71 F4.2 km/s e_DV1665 [0.01/2.5]? Uncertainty in DV1665
73- 77 F5.2 K Tp1667 [-1.6/4.4]? OH 1667MHz line peak temperature
79- 82 F4.2 K e_Tp1667 [0.01/0.3]? Uncertainty in Tp1667
84- 89 F6.2 km/s Vc1667 [-22.7/106.3]? OH 1667MHz line center
velocity
91- 94 F4.2 km/s e_Vc1667 [0/0.9]? Uncertainty in Vc1667
96-100 F5.2 km/s DV1667 [0.3/12.7]? OH 1667MHz line width
102-105 F4.2 km/s e_DV1667 [0.01/2.1]? Uncertainty in DV1667
107-111 F5.2 10+14/cm2 N(OH) [0.2/76.2]? OH column density
113-116 F4.2 10+14/cm2 e_N(OH) [0.1/5.4]? Uncertainty in N(OH)
118-122 F5.2 K Tk [3.7/20.3]? Kinetic temperature
124-127 F4.2 K e_Tk [0.06/1.2]? Uncertainty in Tk
129-134 F6.2 10+15/cm2 N(13CO) [0/102.3]? 13CO column density
136-140 F5.2 10+15/cm2 e_N(13CO) [0/14]? Uncertainty in N(13CO)
142-146 F5.2 10+21/cm N(H2) [0.18/54]? H2 column density
148-152 F5.2 10+21/cm e_N(H2) [0.02/17.2]? Uncertainty in N(H2)
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Byte-by-byte Description of file: table3.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 3 I3 --- Seq [2/141] Source index identifier
5- 20 A16 --- Name Common identifier
22- 28 F7.3 deg GLON [33.10/201.85] Galactic longitude
30- 36 F7.3 deg GLAT [-21.9/9.2] Galactic latitude
38- 42 F5.2 10+14/cm2 N(OH) [1.1/42.2] OH column density
44- 47 F4.2 10+14/cm2 e_N(OH) [0.14/5.4] Uncertainty in N(OH)
49- 53 F5.2 10+18/cm2 N(HINSA) [0.2/14.8] H I Narrow Self-Absorption
column density
55- 58 F4.2 10+18/cm2 e_N(HINSA) [0.07/9.2] Uncertainty in N(HINSA)
60- 63 F4.2 --- p [0.38/0.98] Fraction of background
65- 69 F5.2 10+3/cm3 Den [0.2/18.5]? Density
71- 75 F5.2 10+3/cm3 e_Den [0.1/17.1]? Uncertainty in Den
77- 81 F5.2 10+21/cm2 N(H2) [0.3/18.7] H2 column density
83- 87 F5.2 10+21/cm2 e_N(H2) [0.04/17.2] Uncertainty in N(H2)
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History:
From electronic version of the journal
(End) Prepared by [AAS], Emmanuelle Perret [CDS] 21-Apr-2021