J/ApJ/932/5 Spectral-line survey of SFR W51e1/e2 in 4mm range (Kalenskii+, 2022)
Spectral-line survey of the region of massive star formation W51e1/e2 in the 4mm
wavelength range.
Kalenskii S.V., Kaiser R.I., Bergman P., Olofsson A.O.H., Degtyarev K.D.,
Golysheva P.
<Astrophys. J., 932, 5 (2022)>
=2022ApJ...932....5K 2022ApJ...932....5K
ADC_Keywords: Molecular data; Star Forming Region; Spectra, radio
Keywords: Interstellar medium ; Pre-biotic astrochemistry ; Star forming regions
Abstract:
We present the results of a spectral-line survey of the W51e1/e2
star-forming region at 68-88GHz. 79 molecules and their isotopologues
were detected, from simple diatomic or triatomic molecules, such as
SO, SiO, and CCH, to complex organic compounds, such as CH3OCH3 or
CH3COCH3. A number of lines that are absent from the Lovas list of
molecular lines observed in space were detected, and most of these
were identified. A significant number of the detected molecules are
typical for hot cores. These include the neutral molecules HCOOCH3,
CH3CH2OH, and CH3COCH3, which are currently believed to exist in the
gas phase only in hot cores and shock-heated gas. In addition,
vibrationally excited C4H and HC3N lines with upper-level energies of
several hundred Kelvins were found. Such lines can arise only in hot
gas with temperatures on the order of 100K or higher. Apart from
neutral molecules, various molecular ions were also detected. Some of
these (HC18O+, H13CO+, and HCS+) usually exist in molecular clouds
with high visual extinctions. Potential formation pathways of complex
organic molecules and hydrocarbons, along with nitriles, are
considered. These formation routes are first discussed in the context
of laboratory experiments elucidating the synthesis of organic
molecules in interstellar ices in cold molecular clouds, followed by
sublimation into the gas phase in the hot core stage. Thereafter, we
discuss the predominant formation of hydrocarbons and their nitriles
in the gas phase through bimolecular neutral-neutral reactions.
Description:
The observations were carried out with the 20m radome-enclosed
millimeter-wave radio telescope of the Onsala Space Observatory
(Sweden) at 68-88GHz. 20 observation cycles were performed in
2018 April-May. The antenna was pointed toward e2
(RAJ2000=19:23:43.89,DEJ2000=+14:30:36.4). In this case, the whole
W51e1/e2 region falls within the antenna beam. Pointing errors were
checked using observations of SiO masers at 86GHz, and found to be
within 5".
Objects:
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RA (ICRS) DE Designation(s)
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19 23 43.90 +14 30 34.4 W 51e2 = [M94] 49.5 -0.4 e2
19 23 43.78 +14 30 26.1 W 51e1 = [M94] 49.5 -0.4 e1
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 120 684 Gaussian parameters of detected lines for W51e1/e2
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See also:
V/112 : Catalog of Star-Forming Regions in the Galaxy (Avedisova, 2002)
J/ApJ/720/1055 : VBLA observations of W51 Main/South (Sato+, 2010)
J/A+A/582/A64 : W51/e2 and G34.3+0.2 IRAM spectra (Lykke+, 2015)
J/A+A/595/A27 : JVLA images of W51A (Ginsburg+, 2016)
J/A+A/589/A44 : W51 Main NH3 and CH3OH data cubes (Goddi+, 2016)
J/A+A/631/A137 : IRAS 16293-2422 CH3CCH spectral cubes (Calcutt+, 2019)
J/ApJ/883/129 : ALMA obs. of SFRs toward NGC6334I (El-Abd+, 2019)
J/ApJ/900/L10 : X-band data of GOTHAM Large Project for TMC-1 (McGuire+, 2020)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 1 I1 --- Comp [0/2] Component of blended lines (1)
3- 13 F11.4 MHz Freq [68305.68/87899.5] Rest Frequency
15- 34 A20 --- Mol Molecule
36- 68 A33 --- Trans Transition
70- 75 F6.3 K.km/s TRdV [0.02/39.1]? Integrated intensity, Gaussian fit
77- 81 F5.3 K.km/s e_TRdV [0.004/2.7]? Uncertainty in TRdV
83- 87 F5.2 km/s VLSR [43/66.4]? Radial velocity, relative to LSR,
Gaussian fit
89- 93 F5.3 km/s e_VLSR [0/4.1]? Uncertainty in VLSR
95-100 F6.3 km/s dV [3.4/44]? Linewidth, Gaussian fit
102-106 F5.3 km/s e_dV [0/7.1]? Uncertainty in dV
108-112 F5.3 K Tr [0.002/4.3]? Line peak temperature
114-120 A7 --- Notes Notes (2)
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Note (1): Component of blended lines. Spectral features consisting of two or
more unresolved lines are flagged with Comp>0 and appear consecutively
with the primary line used for the radial velocity listed first. Flag as
follows:
0 = not blended;
1 = the line that is the source of radial velocity in
a blended spectral feature;
2 = other line in a blended spectral feature.
Note (2): Notes as follows:
new = line is absent from the List of Recommended Rest Frequencies for
Observed Interstellar Molecular Microwave Transitions by
Frank J. Lovas;
m = marginal detection;
bl. = the line is blended with the neighboring line,
but the lines are resolved;
s = the sum of AA, EE, AE, and EA CH3OCH3 transitions.
d = doubtful identification
pf = poor fit
mas = maser line
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History:
From electronic version of the journal
(End) Prepared by [AAS], Esther Collas [CDS] 07-May-2024