H2CO and CH3OH maps of the Orion Bar photodissociation region - Astrophysics > Astrophysics of GalaxiesReport as inadecuate




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Abstract: A previous analysis of methanol and formaldehyde towards the Orion Barconcluded that the two molecular species may trace different physicalcomponents, methanol the clumpy material, and formaldehyde the interclumpmedium. To verify this hypothesis, we performed multi-line mapping observationsof the two molecules to study their spatial distributions. The observationswere performed with the IRAM-30m telescope at 218 and 241 GHz, with an angularresolution of ~11-. Additional data for H2CO from the Plateau de Bure arrayare also discussed. The data were analysed using an LVG approach.Both molecules are detected in our single-dish data. Our data show that CH3OHpeaks towards the clumps of the Bar, but its intensity decreases below thedetection threshold in the interclump material. When averaging over a largeregion of the interclump medium, the strongest CH3OH line is detected with apeak intensity of ~0.06K. Formaldehyde also peaks on the clumps, but it is alsodetected in the interclump gas. We verified that the weak intensity of CH3OH inthe interclump medium is not caused by the different excitation conditions ofthe interclump material, but reflects a decrease in the column density ofmethanol. The abundance of CH3OH relative to H2CO decreases by at least oneorder of magnitude from the dense clumps to the interclump medium.



Author: S. Leurini, B. Parise, P. Schilke, J. Pety, R. Rolffs

Source: https://arxiv.org/



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