INTERSTELLAR DETECTION of METHYL ISOCYANATE CH3NCO in Sgr B2(N): A LINK from MOLECULAR CLOUDS to COMETS

D. T. Halfen, V. V. Ilyushin, Lucy M Ziurys

Research output: Contribution to journalArticle

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Abstract

A new interstellar molecule, CH3NCO (methyl isocyanate), has been detected using the 12 m telescope of the Arizona Radio Observatory (ARO). CH3NCO was identified in spectra covering 48 GHz (68-116 GHz) in the 3 mm segment of a broadband survey of Sgr B2(N). Thirty very favorable rotational lines (Ka = 0 and Ka = 1 only; Eu <60 K) originating in five consecutive transitions (J = 8 7, 9 8, 10 9, 11 10, and 12 11) in both the A and E internal rotation species are present in this frequency range. Emission was observed at all of the predicted frequencies, with 17 lines appearing as distinct, uncontaminated spectral features, clearly showing the classic a-type, asymmetric top pattern, with ≈ 20-70 mK. The CH3NCO spectra also appear to exhibit two velocity components near VLSR ≈ 62 and 73 km s-1, both with ΔV1/2 ≈ 10 km s-1 - typical of molecules such as CH2CHCN, HNCO, and HCOOCH3 in Sgr B2(N). The column density of CH3NCO in Sgr B2(N) was determined to be Ntot ≈ 2.3 × 1013 and 1.5 × 1013 cm-2 for the 62 and 73 km s-1 components, corresponding to fractional abundances, relative to H2, of f ≈ 7.6 × 10-12 and 5.0 × 10-12, respectively. CH3NCO was recently detected in volatized material from comet 67P/Churyumov-Gerasimenko by Rosetta's Philae lander, with an abundance ∼1.3% of water; in Sgr B2(N), CH3NCO is roughly ∼0.04% of the H2O abundance.

Original languageEnglish (US)
Article numberL5
JournalAstrophysical Journal Letters
Volume812
Issue number1
DOIs
StatePublished - Oct 10 2015

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comet
relative abundance
isocyanates
observatory
radio
comets
molecules
observatories
coverings
frequency ranges
telescopes
broadband
water
material

Keywords

  • astrochemistry
  • comets: individual (67P/Churyumov-Gerasimenko)
  • ISM: molecules
  • line: identification
  • methods: laboratory: molecular
  • molecular data

ASJC Scopus subject areas

  • Space and Planetary Science
  • Astronomy and Astrophysics

Cite this

INTERSTELLAR DETECTION of METHYL ISOCYANATE CH3NCO in Sgr B2(N) : A LINK from MOLECULAR CLOUDS to COMETS. / Halfen, D. T.; Ilyushin, V. V.; Ziurys, Lucy M.

In: Astrophysical Journal Letters, Vol. 812, No. 1, L5, 10.10.2015.

Research output: Contribution to journalArticle

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title = "INTERSTELLAR DETECTION of METHYL ISOCYANATE CH3NCO in Sgr B2(N): A LINK from MOLECULAR CLOUDS to COMETS",
abstract = "A new interstellar molecule, CH3NCO (methyl isocyanate), has been detected using the 12 m telescope of the Arizona Radio Observatory (ARO). CH3NCO was identified in spectra covering 48 GHz (68-116 GHz) in the 3 mm segment of a broadband survey of Sgr B2(N). Thirty very favorable rotational lines (Ka = 0 and Ka = 1 only; Eu <60 K) originating in five consecutive transitions (J = 8 7, 9 8, 10 9, 11 10, and 12 11) in both the A and E internal rotation species are present in this frequency range. Emission was observed at all of the predicted frequencies, with 17 lines appearing as distinct, uncontaminated spectral features, clearly showing the classic a-type, asymmetric top pattern, with ≈ 20-70 mK. The CH3NCO spectra also appear to exhibit two velocity components near VLSR ≈ 62 and 73 km s-1, both with ΔV1/2 ≈ 10 km s-1 - typical of molecules such as CH2CHCN, HNCO, and HCOOCH3 in Sgr B2(N). The column density of CH3NCO in Sgr B2(N) was determined to be Ntot ≈ 2.3 × 1013 and 1.5 × 1013 cm-2 for the 62 and 73 km s-1 components, corresponding to fractional abundances, relative to H2, of f ≈ 7.6 × 10-12 and 5.0 × 10-12, respectively. CH3NCO was recently detected in volatized material from comet 67P/Churyumov-Gerasimenko by Rosetta's Philae lander, with an abundance ∼1.3{\%} of water; in Sgr B2(N), CH3NCO is roughly ∼0.04{\%} of the H2O abundance.",
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N2 - A new interstellar molecule, CH3NCO (methyl isocyanate), has been detected using the 12 m telescope of the Arizona Radio Observatory (ARO). CH3NCO was identified in spectra covering 48 GHz (68-116 GHz) in the 3 mm segment of a broadband survey of Sgr B2(N). Thirty very favorable rotational lines (Ka = 0 and Ka = 1 only; Eu <60 K) originating in five consecutive transitions (J = 8 7, 9 8, 10 9, 11 10, and 12 11) in both the A and E internal rotation species are present in this frequency range. Emission was observed at all of the predicted frequencies, with 17 lines appearing as distinct, uncontaminated spectral features, clearly showing the classic a-type, asymmetric top pattern, with ≈ 20-70 mK. The CH3NCO spectra also appear to exhibit two velocity components near VLSR ≈ 62 and 73 km s-1, both with ΔV1/2 ≈ 10 km s-1 - typical of molecules such as CH2CHCN, HNCO, and HCOOCH3 in Sgr B2(N). The column density of CH3NCO in Sgr B2(N) was determined to be Ntot ≈ 2.3 × 1013 and 1.5 × 1013 cm-2 for the 62 and 73 km s-1 components, corresponding to fractional abundances, relative to H2, of f ≈ 7.6 × 10-12 and 5.0 × 10-12, respectively. CH3NCO was recently detected in volatized material from comet 67P/Churyumov-Gerasimenko by Rosetta's Philae lander, with an abundance ∼1.3% of water; in Sgr B2(N), CH3NCO is roughly ∼0.04% of the H2O abundance.

AB - A new interstellar molecule, CH3NCO (methyl isocyanate), has been detected using the 12 m telescope of the Arizona Radio Observatory (ARO). CH3NCO was identified in spectra covering 48 GHz (68-116 GHz) in the 3 mm segment of a broadband survey of Sgr B2(N). Thirty very favorable rotational lines (Ka = 0 and Ka = 1 only; Eu <60 K) originating in five consecutive transitions (J = 8 7, 9 8, 10 9, 11 10, and 12 11) in both the A and E internal rotation species are present in this frequency range. Emission was observed at all of the predicted frequencies, with 17 lines appearing as distinct, uncontaminated spectral features, clearly showing the classic a-type, asymmetric top pattern, with ≈ 20-70 mK. The CH3NCO spectra also appear to exhibit two velocity components near VLSR ≈ 62 and 73 km s-1, both with ΔV1/2 ≈ 10 km s-1 - typical of molecules such as CH2CHCN, HNCO, and HCOOCH3 in Sgr B2(N). The column density of CH3NCO in Sgr B2(N) was determined to be Ntot ≈ 2.3 × 1013 and 1.5 × 1013 cm-2 for the 62 and 73 km s-1 components, corresponding to fractional abundances, relative to H2, of f ≈ 7.6 × 10-12 and 5.0 × 10-12, respectively. CH3NCO was recently detected in volatized material from comet 67P/Churyumov-Gerasimenko by Rosetta's Philae lander, with an abundance ∼1.3% of water; in Sgr B2(N), CH3NCO is roughly ∼0.04% of the H2O abundance.

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