J/ApJ/883/129 ALMA obs. of star-forming regions toward NGC6334I (El-Abd+, 2019)
Interstellar glycolaldehyde, methyl formate, and acetic acid.
I. A bimodal abundance pattern in star-forming regions.
El-Abd S.J., Brogan C.L., Hunter T.R., Willis E.R., Garrod R.T.,
McGuire B.A.
<Astrophys. J., 883, 129 (2019)>
=2019ApJ...883..129E 2019ApJ...883..129E
ADC_Keywords: Atomic physics; Molecular data; Radio lines; Star Forming Region;
Interstellar medium
Keywords: astrochemistry ; ISM: molecules
Abstract:
The relative column densities of the structural isomers methyl
formate, glycolaldehyde, and acetic acid are derived for a dozen
positions toward the massive star-forming regions MM1 and MM2 in the
NGC 6334I complex, which are separated by ∼4000au. Relative column
densities of these molecules are also gathered from the literature for
13 other star-forming regions. In this combined data set, a clear
bimodal distribution is observed in the relative column densities of
glycolaldehyde and methyl formate. No such distribution is evident
with acetic acid. The two trends are comprised of star-forming regions
with a variety of masses, suggesting that there must be some other
common parameter that is heavily impacting the formation of
glycolaldehyde. This is indicative of some demonstrable
differentiation in these cores; studying the abundances of these
isomers may provide a clue as to the integral chemical processes
ongoing in a variety of protostellar environments.
Description:
The Atacama Large Millimeter/sub-millimeter Array (ALMA) data toward
NGC 6334I were observed during Cycle 3 in 2016, project code
2015.A.00022.T. The data were calibrated using the ALMA Cycle 4
pipeline (CASA 4.7.2). The observations were centered at
RAJ2000=17:20:53.36,DEJ2000=-35:47:00.0 and had a nominal resolution
of 0.24"x0.17" (-83°), a full width half-power of the primary beam
of 20", a spectral resolution of 1.1km/s, and an rms per channel of
2.0mJy/beam (0.62K).
The first set of spectral windows were centered at 280.1, 282.0,
292.1, and 294.0GHz. The second set of spectral windows were centered
at 337.1, 339.0, 349.1, and 351.0GHz.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 84 112 Transitions used to calculate isomer
column densities in NGC 6334I
table2.dat 61 12 Physical parameters for spectra extraction
locations in NGC 6334I
table3.dat 118 25 C2H4O2 isomer column densities in each source
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See also:
J/A+A/466/989 : Hot ammonia from NGC 6334I and NGC 6334I(N) (Beuther+, 2007)
J/ApJ/723/845 : The submillimeter spectrum of glycolaldehyde (Carroll+, 2010)
J/A+A/532/A32 : HCOOCH3 map of Orion-KL (Favre+, 2011)
J/A+A/559/A47 : Sgr B2(N) and Sgr B2(M) IRAM 30m line survey (Belloche+, 2013)
J/A+A/568/A65 : NGC 7129 FIRS 2 interferometric 1-D spectrum (Fuente+, 2014)
J/A+A/582/A64 : W51/e2 and G34.3+0.2 IRAM spectra (Lykke+, 2015)
J/ApJ/851/L46 : CH3OCH2OH ALMA detection in NGC 6334I (McGuire+, 2017)
J/A+A/598/A59 : G31.41+0.31 SMA spectra (Rivilla+, 2017)
J/ApJ/866/87 : VLA 22GHz water masers obs. in NGC6334I-MM1 (Brogan+, 2018)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 8 A8 --- Reg MM1 and MM2 region identifier
10- 23 A14 --- Mol Molecule identifier
25- 26 I2 --- J0 [13/34] The J' level
28- 29 A2 --- Ka0 The Ka' level
31- 32 A2 --- Kc0 The Kc' level
34- 35 I2 --- J1 [12/33] The J" level
37- 38 A2 --- Ka1 The Ka" level
40- 41 A2 --- Kc1 The Kc" level
43- 48 A6 --- A/E Symmetry
50- 60 F11.4 MHz Freq [279230/351209.4] Frequency
62- 68 F7.3 K Eup [70.47/442.07] Upper state energy
70- 78 F9.5 D2 Sijmu2 [2/320.1] Intrinsic line strength time
the squared dipole moment
80- 84 F5.3 Jy/beam Iobs [0.02/0.43] Observed intensity
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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- 8 A8 --- Reg MM1 and MM2 region identifier
10- 11 I2 h RAh [17] Hour of right ascension (J2000)
13- 14 I2 min RAm [20] Minute of right ascension (J2000)
16- 21 F6.3 s RAs [53.15/53.48] Second of right ascension (J2000)
23 A1 --- DE- [-] Sign of declination (J2000)
24- 25 I2 deg DEd [35] Degree of declination (J2000)
27- 28 I2 arcmin DEm [46] Arcminute of declination (J2000)
30- 35 F6.3 arcsec DEs [57.1/59.5] Arcsecond of declination (J2000)
37- 39 I3 K Tex [135/285] Excitation temperature
41- 45 F5.1 K TbgLo [21.8/159.3] Background temperature for the lower
sideband of the ALMA data
47- 51 F5.1 K TbgUp [27.8/192.7] Background temperature for the upper
sideband of the ALMA data
53- 56 F4.1 km/s VLSR [-9/-4.4] Local Standard of Rest velocity
58- 61 F4.2 km/s DelV [2.5/4.5] Linewidth ΔV
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Byte-by-byte Description of file: table3.dat
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Bytes Format Units Label Explanations
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1- 16 A16 --- Source Source name
18- 25 A8 --- Reg MM1 and MM2 region identifier
27- 32 E6.2 --- NMF [5.4e+13/7e+18] Methyl formate column density
34- 39 E6.2 --- e_NMF [8e+12/3e+18] NMF uncertainty
41 A1 --- l_NGA Limit flag on NGA
42- 47 E6.2 --- NGA [3.4e+13/3e+17] Glycolaldehyde column density
49- 54 E6.2 --- e_NGA [7e+12/2e+17]? NGA uncertainty
56 A1 --- l_NAA Limit flag on NAA
57- 62 E6.2 --- NAA [2.1e+13/7e+17]? Acetic acid column density
64- 69 E6.2 --- e_NAA [7e+14/1e+17]? NAA uncertainty
71- 72 A2 --- l_MF/GA [≥ ] Limit flag on MF/GA
73- 77 F5.1 --- MF/GA [1.6/667]? Methyl formate to glycolaldehyde
(MF/GA) ratio
79- 82 F4.1 --- e_MF/GA [0.4/85]? MF/GA uncertainty
84- 88 A5 --- Class MF/GA classification (see Section 4)
90- 101 A12 --- Mass Region mass (1)
103- 106 A4 --- Obs Observation type (Int.=Interferometer;
S.D.=Single-dish)
108- 110 A3 --- Beam Beam corrected (2)
112 A1 --- f_Beam [a] Flag on Beam (3)
114- 118 A5 --- Ref Reference(s) (4)
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Note (1): The region masses given are taken directly from the respective
reference.
Note (2):
M = These beams appear well-matched to the source size as observed, and thus
no correction was made by the authors.
Note (3):
a = A beam correction was applied to glycolaldehyde for this work.
See Appendix A
Note (4): Reference as follows:
1 = Favre et al. (2011, J/A+A/532/A32)
2 = Belloche et al. (2013, J/A+A/559/A47)
3 = Lykke et al. (2015, J/A+A/582/A64)
4 = Remijan et al. (2002ApJ...576..264R 2002ApJ...576..264R)
5 = Remijan et al. (2003ApJ...590..314R 2003ApJ...590..314R)
6 = Rivilla et al. (2017, J/A+A/598/A59)
7 = Calcutt et al. (2014MNRAS.443.3157C 2014MNRAS.443.3157C)
8 = Fuente et al. (2014, J/A+A/568/A65)
9 = Jorgensen et al. (2016A&A...595A.117J 2016A&A...595A.117J)
10 = Lefloch et al. (2017MNRAS.469L..73L 2017MNRAS.469L..73L)
11 = Taquet et al. (2015ApJ...804...81T 2015ApJ...804...81T).
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History:
From electronic version of the journal
(End) Prepared by [AAS], Emmanuelle Perret [CDS] 05-Mar-2021