2022A&A...666A..50V


Query : 2022A&A...666A..50V

2022A&A...666A..50V - Astronomy and Astrophysics, volume 666A, 50 (2022/10-1)

Millimeter wave spectrum and search for vinyl isocyanate toward Sgr B2(N) with ALMA.

VAVRA K., KOLESNIKOVA L., BELLOCHE A., GARROD R.T., KOUCKY J., UHLIKOVA T., LUKOVA K., GUILLEMIN J.-C., KANIA P., MULLER H.S.P., MENTEN K.M. and URBAN S.

Abstract (from CDS):


Context. The interstellar detections of isocyanic acid (HNCO), methyl isocyanate (CH3NCO), and very recently also ethyl isocyanate (C2H5NCO) invite the question of whether or not vinyl isocyanate (C2H3NCO) can be detected in the interstellar medium. There are only low-frequency spectroscopic data (<40 GHz) available for this species in the literature, which makes predictions at higher frequencies rather uncertain, which in turn hampers searches for this molecule in space using millimeter (mm) wave astronomy.
Aims. The aim of the present study is on one hand to extend the laboratory rotational spectrum of vinyl isocyanate to the mm wave region and on the other to search, for the first time, for its presence in the high-mass star-forming region Sgr B2, where other isocyanates and a plethora of complex organic molecules are observed.
Methods. We recorded the pure rotational spectrum of vinyl isocyanate in the frequency regions 127.5-218 and 285-330 GHz using the Prague mm wave spectrometer. The spectral analysis was supported by high-level quantum-chemical calculations. On the astronomy side, we assumed local thermodynamic equilibrium to compute synthetic spectra of vinyl isocyanate and to search for it in the ReMoCA survey performed with the Atacama Large Millimeter/submillimeter Array (ALMA) toward the high-mass star-forming protocluster Sgr B2(N). Additionally, we searched for the related molecule ethyl isocyanate in the same source.
Results. Accurate values for the rotational and centrifugal distortion constants are reported for the ground vibrational states of trans and cis vinyl isocyanate from the analysis of more than 1000 transitions. We report nondetections of vinyl and ethyl isocyanate toward the main hot core of Sgr B2(N). We find that vinyl and ethyl isocyanate are at least 11 and 3 times less abundant than methyl isocyanate in this source, respectively.
Conclusions. Although the precise formation mechanism of interstellar methyl isocyanate itself remains uncertain, we infer from existing astrochemical models that our observational upper limit for the CH3NCO:C2H5NCO ratio in Sgr B2(N) is consistent with ethyl isocyanate being formed on dust grains via the abstraction or photodissociation of an H atom from methyl isocyanate, followed by the addition of a methyl radical. The dominance of such a process for ethyl isocyanate production, combined with the absence of an analogous mechanism for vinyl isocyanate, would indicate that the ratio C2H3NCO:C2H5NCO should be less than unity. Even though vinyl isocyanate was not detected toward Sgr B2(N), the results of this work represent a significant improvement on previous low-frequency studies and will help the astronomical community to continue searching for this species in the Universe.

Abstract Copyright: © K. Vávra et al. 2022

Journal keyword(s): astrochemistry - ISM: molecules - line: identification - ISM: individual objects: Sgr B2 - methods: laboratory: molecular

VizieR on-line data: <Available at CDS (J/A+A/666/A50): tablea2.dat tablea3.dat tablea5.dat tablea6.dat>

Simbad objects: 16

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Number of rows : 16
N Identifier Otype ICRS (J2000)
RA
ICRS (J2000)
DEC
Mag U Mag B Mag V Mag R Mag I Sp type #ref
1850 - 2024
#notes
1 TMC-1 MoC 04 41 45.9 +25 41 27           ~ 1681 0
2 NAME Orion-KL SFR 05 35 14.16 -05 22 21.5           ~ 2299 1
3 MSXDC G328.25-0.51 a cor 15 57 55 -53 57.4           ~ 13 0
4 GAL 331.512-00.103 out 16 12 10.046 -51 28 37.32           ~ 10 0
5 IRAS 16293-2422 cor 16 32 22.56 -24 28 31.8           ~ 1255 1
6 NAME NGC 6334-I Cl* 17 20 53.35 -35 47 01.5           ~ 344 0
7 NAME Galactic Center reg 17 45 39.60213 -29 00 22.0000           ~ 14463 0
8 [QSR2011] Sgr B2(N)-SMA2 cor 17 47 19.885 -28 22 13.29           ~ 94 0
9 [BMG2016] Sgr B2(N1) cor 17 47 19.889 -28 22 18.22           ~ 57 0
10 NAME Sgr B2 (North) Rad 17 47 20.2 -28 22 21           ~ 675 1
11 NAME Sgr B2 MoC 17 47 20.4 -28 23 07           ~ 2271 1
12 GCM +0.693 -0.027 MoC 17 47 21.9 -28 21 27           ~ 63 0
13 GAL 010.47+00.03 HII 18 08 38.4 -19 51 52           ~ 148 0
14 LDN 483 DNe 18 17 35 -04 39.8           ~ 317 0
15 GCNM 23 Y*O 18 29 49.63 +01 15 21.9           ~ 273 2
16 IRAS 18449-0115 cor 18 47 34.27 -01 12 43.2           ~ 390 0

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