2010/01/06 by S. Leurini, B. Parise, P. Schilke +2 · 1 citation
Chemistry · Earth and Planetary Sciences · Physics and Astronomy · #Analytical Chemistry (journal) #Astronomy #Astrophysics #Astrophysics and Star Formation Studies #Atmospheric Ozone and Climate #Bar (unit) #Chemistry #Chromatography #Emission spectrum #Excitation temperature #Formaldehyde #Geometry #Intensity (physics) #Isotopologue #Line (geometry) #Methanol #Molecular Spectroscopy and Structure #Molecule #Optics #Photochemistry #Photodissociation #Physics #Plateau de Bure Interferometer #Spectral line #Star formation #Stars #Telescope #astro-ph.GA
paper · pdf · doi:10.1051/0004-6361/200912484
11 pages, accepted for publication in A&A
arxiv created 2010/01/06 · openalex publication_date 2010/01/15 · arxiv updated 2015/05/14 · openalex created_date 2016/06/24 · openalex updated_date 2026/08/05
<i>Context. <i/>A previous analysis of methanol and formaldehyde towards the Orion Bar concludes that the two molecular species may trace different physical components, methanol the clumpy material, and formaldehyde the interclump medium.<i>Aims. <i/>To verify this hypothesis, we performed multi-line mapping observations of the two molecules to study their spatial distributions.<i>Methods. <i/>The observations were performed with the IRAM-30 m telescope at 218 and 241 GHz, with an angular resolution of . Additional data for H<sub>2<sub/>CO from the Plateau de Bure array are also discussed. The data were analysed using an LVG approach.<i>Results. <i/>Both molecules are detected in our single-dish data. Our data show that CH<sub>3<sub/>OH peaks towards the clumps of the Bar, but its intensity decreases below the detection threshold in the interclump material. When averaging over a large region of the interclump medium, the strongest CH<sub>3<sub/>OH line is detected with a peak intensity of ~0.06 K. Formaldehyde also peaks on the clumps, but it is also detected in the interclump gas.<i>Conclusions. <i/>We verified that the weak intensity of CH<sub>3<sub/>OH in the interclump medium is not caused by the different excitation conditions of the interclump material, but reflects a decrease in the column density of methanol. The abundance of CH<sub>3<sub/>OH relative to H<sub>2<sub/>CO decreases by at least one order of magnitude from the dense clumps to the interclump medium.