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تسجيل مستخدم جديدThe complexity of Orion: an ALMA view. II. gGg-Ethylene Glycol and Acetic Acid
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We report the first detection and high angular resolution (1.8 $times$ 1.1) imaging of acetic acid (CH$_3$COOH) and gGg$^{prime}$--ethylene glycol (gGg$^{prime}$(CH$_2$OH)$_2$) towards the Orion Kleinmann--Low nebula. The observations were carried out at $sim$1.3mm with ALMA during the Cycle~2. A notable result is that the spatial distribution of the acetic acid and ethylene glycol emission differs from that of the other O-bearing molecules within Orion-KL. Indeed, while the typical emission of O-bearing species harbors a morphology associated with a V-shape linking the Hot Core region to the Compact Ridge (with an extension towards the BN object), that of acetic acid and ethylene glycol mainly peaks at about 2 southwest from the hot core region (near sources I and n). We find that the measured CH$_3$COOH:aGg$^{prime}$(CH$_2$OH)$_2$ and CH$_3$COOH:gGg$^{prime}$(CH$_2$OH)$_2$ ratios differ from the ones measured towards the low-mass protostar IRAS 16293--2422 by more than one order of magnitude. Our best hypothesis to explain these findings is that CH$_3$COOH, aGg$^{prime}$(CH$_2$OH)$_2$ and gGg$^{prime}$(CH$_2$OH)$_2$ are formed on the icy-surface of grains and then released into the gas-phase, via co-desorption with water, due to a bullet of matter ejected during the explosive event that occurred in the heart of the Nebula about 500-700 years ago.
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