J/A+A/644/A160 ATLASGAL-selected massive clumps. Chemistry of PDR (Kim+, 2020)
ATLASGAL-selected massive clumps in the inner Galaxy.
VIII. Chemistry of photodissociation regions.
Kim W.-J., Wyrowski F., Urquhart J.S., Perez-Beaupuits J.P., Pillai T.,
Tiwari M., Menten K.M.
<Astron. Astrophys. 644, A160 (2020)>
=2020A&A...644A.160K 2020A&A...644A.160K (SIMBAD/NED BibCode)
ADC_Keywords: Surveys ; Interstellar medium ; H II regions
Keywords: astrochemistry - surveys - ISM: molecules - HII regions -
photo-dominated regions
Abstract:
We study ten molecular transitions obtained from an unbiased 3mm
molecular line survey using the IRAM 30m telescope toward 409 compact
dust clumps identified by the APEX Telescope Large Area Survey of the
Galaxy (ATLASGAL) to better understand the photodissociation regions
(PDRs) associated with these clumps. The main goal of this study is to
investigate whether the abundances of the selected molecules show any
variations resulting from the PDR chemistry in different clump
environments.
We selected HCO, HOC+, C2H, c-C3H2, CN, H13CN, HC15N, and
HN13C as PDR tracers, and H13CO+ and C18O as dense gas
tracers. By using estimated optical depths of C2H and H13CN and
assuming optically thin emission for other molecular transitions, we
derived the column densities of those molecules and their abundances.
To assess the influence of the presence and strength of ultra- violet
radiation, we compare abundances of three groups of the clumps: HII
regions, infrared bright non-HII regions, and infrared dark non-HII
regions.
We detected C18O, H13CO+, C2H, c-C3H2, CN, and HN13C
toward most of the observed dust clumps (detection rate >94%), and
H13CN is also detected with a detection rate of 75%. On the other
hand, HCO and HC15N show detection rates of 32% and 39%,
respectively, toward the clumps, which are mostly associated with HII
region sources: Detection rates of HCO and HC15N toward the HII
regions are 66% and 79%. We find that the abundances of HCO, CN,
C2H, and c-C3H2 decrease as the H2 column density increases,
indicating high visual extinction, while those of high-density tracers
(i.e., H13CO+ and HC15N) are constant. In addition,
N(HCO)/N(H13CO+) ratios significantly decrease as H2 column
density increases, and, in particular, 82 clumps have X(HCO)≥10-10
and N(HCO)/N(H13CO+)≳1, which are indications of far-ultraviolet
(FUV) chemistry. This suggests the observed HCO abundances are likely
associated with FUV radiation illuminating the PDRs. We also find that
high N(c-C3H2)/N(C2H) ratios found for HII regions that have
high HCO abundances (≳10-10) are associated with more evolved
clumps with high Lbol/Mclump. This trend might be associated with
gain-surface processes, which determine the initial abundances of
these molecules, and time-dependent effects in the clumps
corresponding to the envelopes around dense PDRs and HII regions. In
addition, some fraction of the measured abundances of the small
hydrocarbons of the HII sources may be the result of the
photodissociation of PAH molecules.
Description:
List of the observed source list, gaussian and hyperfine structure fit
parameters of the selected molecular transitions, and molecular column
densities are provided.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table2.dat 105 409 List of observed sources
t3cch.dat 71 328 Line parameters of hyperfine lines of CCH
t3h13cn.dat 71 329 Line parameters of hyperfine lines of H13CN
t4c-c3h2.dat 73 402 Gaussian line parameters of c-C3H2
t4c18o.dat 73 384 Gaussian line parameters of C18O
t4cn.dat 73 330 Gaussian line parameters of CN
t4h13cop.dat 73 399 Gaussian line parameters of H13CO+
t4hc15n.dat 73 161 Gaussian line parameters of HC15N
t4hco.dat 73 128 Gaussian line parameters of HCO
t4hn13c.dat 73 383 Gaussian line parameters of HN13C
table6.dat 100 393 Column density of molecules
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See also:
J/A+A/570/A65 : ATLASGAL massive clumps CO depletion (Giannetti+, 2014)
J/A+A/586/A149 : SiO in ATLASGAL-selected massive clumps (Csengeri+, 2016)
J/A+A/599/A139 : ATLASGAL massive clumps dust characterization (Koenig+, 2017)
J/A+A/602/A37 : Millimeter RRL in ATLASGAL-selected massive clumps (Kim+ 2017)
J/A+A/603/A33 : Temperature evolution in massive clumps (Giannetti+, 2017)
J/A+A/611/A6 : ATLASGAL massive clumps H2CO data (Tang+, 2018)
J/A+A/622/A135 : Mid-J CO emission of Top100 clumps (Navarete+, 2019)
J/MNRAS/473/1059 : Complete sample of Galactic clump properties
(Urquhart+, 2018)
Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
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1- 18 A18 --- Name ATLASGAL clump name
(AGAL LLL.lll+BB.bbb or GLLL.lll+B.bbb)
20- 21 I2 h RAh Right ascension (J2000)
23- 24 I2 min RAm Right ascension (J2000)
26- 29 F4.1 s RAs Right ascension (J2000)
31 A1 --- DE- Declination sign (J2000)
32- 33 I2 deg DEd Declination (J2000)
35- 36 I2 arcmin DEm Declination (J2000)
38- 39 I2 arcsec DEs Declination (J2000)
41- 44 F4.1 kpc Dist ? Distance of source
46- 49 F4.1 K Tdust ? Temperature of dust
51- 57 A7 --- Type Clump type related with HII presence
59- 74 A16 --- Class Classification of clump type
75-105 A31 --- Com Comments
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Byte-by-byte Description of file: t3cch.dat t3h13cn.dat
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Bytes Format Units Label Explanations
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1- 18 A18 --- Name ATLASGAL clump name
20- 24 A5 --- Line Line (1)
26- 31 F6.2 km/s Vlsr LSR velocity of Line
33- 36 F4.2 km/s e_Vlsr Uncertainty on Line velocity
38- 42 F5.2 km/s dv Line linewidth
44- 47 F4.2 km/s e_dv Uncertainty on Line linewidth
49- 54 F6.2 --- Tautotal Total optical thickness
56- 60 F5.2 --- e_Tautotal Uncertainty on optical thickness
62- 66 F5.2 K Tmb Peak intensity of the Line (2)
68- 71 F4.2 K rms rms noise per channel
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Note (1): Lines are CCH (N = 1-0) or H13CN (N = 1-0)
Note (2): For CCH, NJF = 1(3/2)2-0(1/2)1, for H13CN, JF=12-01
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Byte-by-byte Description of file: t4*.dat
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Bytes Format Units Label Explanations
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1- 18 A18 --- Name ATLASGAL clump name
20- 25 A6 --- Line Line (1)
27- 31 F5.2 K.km/s Area Velocity integrated intensity
33- 36 F4.2 K.km/s e_Area Uncertainty of Area
38- 43 F6.2 km/s Vlsr Peak velocity of Line
46- 50 F5.2 km/s e_Vlsr Uncertainty of Line velocity
52- 56 F5.2 km/s dv Line linewidth
58- 62 F5.2 km/s e_dv Uncertainty of Line linewidth
64- 68 F5.2 K Tmb Peak intensity of Line
70- 73 F4.2 K rms rms noise per channel
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Note (1): Lines are C18O (1-0), HCO (1-0), H13CO+ (1-0), c-C3H2 (1-0),
CN (1-0), HC15N (1-0) and HN13C (1-0).
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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- 18 A18 --- Name ATLASGAL clump name
20- 27 E8.3 cm-2 N(C18O) ? Column density of C18O
29- 36 E8.3 cm-2 N(HCO) ? Column density of HCO
38- 45 E8.3 cm-2 N(H13CO+) ? Column density of H13CO+
47- 54 E8.3 cm-2 N(CCH) ? Column density of CCH
56- 63 E8.3 cm-2 N(c-C3H2) ? Column density of c-C3H2
65- 72 E8.3 cm-2 N(CN) ? Column density of CN
74- 81 E8.3 cm-2 N(HC15N) ? Column density of HC15N
83- 91 E9.4 cm-2 N(H13CN) ? Column density of H13CN
93-100 E8.3 cm-2 N(HN13C) ? Column density of HN13C
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Acknowledgements:
Won-Ju Kim, kim(at)iram.es
References:
Urquhart et al., 2018MNRAS.473..1059U, Cat. J/MNRAS/473/1059
Giannetti et al., Paper I 2014A&A...570A..65G 2014A&A...570A..65G, cat. J/A+A/570/A65
Csengeri et al., Paper II 2016A&A...586A.149C 2016A&A...586A.149C, Cat. J/A+A/586/A149
Konig et al., Paper III 2017A&A...599A.139K 2017A&A...599A.139K, Cat. J/A+A/599/A139
Kim et al., Paper IV 2017A&A...602A..37K 2017A&A...602A..37K, Cat. J/A+A/602/A37
Giannetti et al., Paper V 2017A&A...603A..33G 2017A&A...603A..33G, Cat. J/A+A/603/A33
Tang et al., Paper VI 2018A&A...611A...6T 2018A&A...611A...6T, Cat. J/A+A/611/A6
Navarete et al., Paper VII 2019A&A...622A.135N 2019A&A...622A.135N, Cat. J/A+A/622/A135
(End) Won-Ju Kim [IRAM, Spain], Patricia Vannier [CDS] 04-Dec-2020