J/A+A/658/A85 Search for thioacetamide CH3CSNH2 in the ISM (Remijan+, 2022)
Expanding the submillimeter wave spectroscopy and astronomical search for
thioacetamide (CH3CSNH2) in the ISM.
Remijan A., Xue C., Margules L., Belloche A., Motiyenko R.A., Carder J.,
Codella C., Balucani N., Brogan C.L., Ceccarelli C., Hunter T.R., Maris A.,
Melandri S., Siebert M., McGuire B.A.
<Astron. Astrophys. 658, A85 (2022)>
=2022A&A...658A..85R 2022A&A...658A..85R (SIMBAD/NED BibCode)
ADC_Keywords: Atomic physics ; Interstellar medium
Keywords: astrochemistry - line: identification - ISM: molecules -
radio lines: ISM - submillimeter: ISM - methods: laboratory: molecular
Abstract:
One of the biggest unsolved mysteries of modern astrochemistry is
understanding chemical formation pathways in the interstellar medium
(ISM) and circumstellar environments (CSEs). The detections (or even
nondetections) of molecules composed of low-abundance atomic species
(such as S, P, Si, and Mg) may help to constrain chemical pathways.
Thioacetamide (CH3CSNH2) is the sulfur analog to acetemide
(CH3CONH2) and it is a viable candidate to search for in
astronomical environments - specifically toward regions where other
S-bearing molecules have been found and, if possible, that also
contain a detection of CH3CONH2. If detected, it would not only
continue to expand the view of molecular complexity in astronomical
environments, but also help to better elucidate the possible formation
pathways of these types of species in these environments.
Our aim is to expand the frequency range of the measured rotational
spectrum of CH3CSNH2 beyond 150GHz and then to use those
measurements to extend the search for this species in the ISM. The new
laboratory measurements and expanded search cover more parameter space
for determining under what conditions CH3CSNH2 may be detected,
leading to possible constraints on the formation of large S-bearing
molecules found in the ISM.
The rotational spectrum of CH3CSNH2 was investigated up to 650GHz.
Using the newly refined spectrum of CH3CSNH2, as well as
additional spectroscopic data on the chemically related species
CH3CONH2, a variety of astronomical sources were searched
including data from the following large surveys: Prebiotic
Interstellar Molecule Survey (PRIMOS) conducted with the Green Bank
Telescope (GBT); Exploring molecular complexity with ALMA (EMoCA)
conducted with the Atacama Large Millimeter/submillimeter Array
(ALMA); and Astrochemical Surveys At IRAM (ASAI) conducted with the
Institut de Radioastronomie Millim'etrique (IRAM) 30m Telescope.
A total of 1428 transitions from the vt=0 state with maximum values
J=47 and Ka=20 in the range up to 330GHz, and J=95 and Ka=20 in
the range from 400-660GHz were assigned. We also assigned 321
transitions from the v_t=1 state with the maximum values J=35 and
Ka=9 up to 330GHz. We achieved a final fit with a root-mean-square
deviation of 43.4kHz that contains 2035 measured lines from our study
and the literature for vt=0 and vt=1 states of A and E symmetries.
The final fit is based on the rho-axis- method (RAM) Hamiltonian model
that includes 40 parameters. An astronomical search for CH3CSNH2
was conducted based on all the new spectroscopic data. No transitions
of CH3CSNH2 were detected toward any of the sources contained in
our survey. Using the appropriate telescope and physical parameters
for each astronomical source, upper limits to the column densities
were found for CH3CSNH2 toward each source.
Description:
The table contains the list of measured transitions of both the A- and
E- symmetry states of thioacetamide (CH3CSNH2). Frequencies are
given in MHz and lower state energy levels are given in cm-1.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table.dat 75 139819 Transitions of thioacetamide
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Byte-by-byte Description of file: table.dat
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Bytes Format Units Label Explanations
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3- 13 F11.4 MHz Freq Frequency of the line
14- 21 F8.4 MHz e_Freq Estimated or experimental error
22- 29 F8.4 [nm2.MHz] logInt Base 10 logarithm of the integrated intensity
31 I1 --- DOF Degrees of freedom
33- 41 F9.4 cm-1 Elow Lower state energy
42- 44 I3 --- gup Upper state degeneracy
47- 51 I5 --- Tag Species tag or molecular identifier
52- 63 A12 --- QNFMT Identifies the format of the quantum numbers
68- 75 A8 --- QN Quantum numbers coded according to QNFMT
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Acknowledgements:
Anthony Remijan, aremijan(at)nrao.edu
(End) Patricia Vannier [CDS] 15-Dec-2021