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Authors:N. Brouillet, D. Despois, A. Baudry, T.-C. Peng, C. Favre, A. Wootten, A. J. Remijan, T. L. Wilson, F. Combes, G. Wlodarczak
Download PDF Abstract: We used several data sets from the Plateau de Bure Interferometer to map thedimethyl ether emission in Orion-KL with different arcsec spatial resolutionsand different energy levels to compare with our previous methyl formate maps.Our data show remarkable similarity between the dimethyl ether (CH3OCH3) andthe methyl formate (HCOOCH3) distributions even on a small scale (1.8″x0.8″ orabout 500 AU). This long suspected similarity, seen from both observational andtheoretical arguments, is demonstrated with unprecedented confidence, with acorrelation coefficient of maps of 0.8.A common precursor is the simplest explanation of our correlation.Comparisons with previous laboratory work and chemical models suggest the majorrole of grain surface chemistry and a recent release, probably with littleprocessing, of mantle molecules by shocks. In this case the CH3O radicalproduced from methanol ice would be the common precursor (whereas ethanol,C2H5OH, is produced from the radical CH2OH). The alternative gas phase scheme,where protonated methanol CH3OH2+ is the common precursor to produce methylformate and dimethyl ether through reactions with HCOOH and CH3OH, is alsocompatible with our data. Our observations cannot yet definitely allow a choicebetween the different chemical processes, but the tight correlation between thedistributions of HCOOCH3 and CH3OCH3 strongly contrasts with the differentbehavior we observe for the distributions of ethanol and formic acid. Thisprovides a very significant constraint on models.
|Comments:||10 pages, 8 figures, to be published in Astronomy & Astrophysics|
|Subjects:||Astrophysics of Galaxies (astro-ph.GA)|
From: Nathalie Brouillet