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 language | English (US) |
|---|---|
| Article number | L5 |
| Journal | Astrophysical Journal Letters |
| Volume | 812 |
| Issue number | 1 |
| DOIs | |
| State | Published - Oct 10 2015 |
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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 journal › Article
}
TY - JOUR
T1 - INTERSTELLAR DETECTION of METHYL ISOCYANATE CH3NCO in Sgr B2(N)
T2 - A LINK from MOLECULAR CLOUDS to COMETS
AU - Halfen, D. T.
AU - Ilyushin, V. V.
AU - Ziurys, Lucy M
PY - 2015/10/10
Y1 - 2015/10/10
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.
KW - astrochemistry
KW - comets: individual (67P/Churyumov-Gerasimenko)
KW - ISM: molecules
KW - line: identification
KW - methods: laboratory: molecular
KW - molecular data
UR - http://www.scopus.com/inward/record.url?scp=84946095494&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=84946095494&partnerID=8YFLogxK
U2 - 10.1088/2041-8205/812/1/L5
DO - 10.1088/2041-8205/812/1/L5
M3 - Article
AN - SCOPUS:84946095494
VL - 812
JO - Astrophysical Journal Letters
JF - Astrophysical Journal Letters
SN - 2041-8205
IS - 1
M1 - L5
ER -