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Autores
Fuente, A.; García-Burillo, S.; Gerin, M.; Teyssier, D.; Usero, A.; Rizzo, J. R.; de Vicente, P.
Resumen
The nucleus of M82 has been mapped in several 3 and 1 mm lines of CN, HCN, C2H, c-C3H2, CH3C2H, HC3N, and HOC+ using the IRAM 30 m telescope. These species have been purposely selected as good tracers of photon-dominated chemistry. We have measured [CN]/[HCN]~5 in the inner 650 pc galaxy disk. Furthermore, we have detected the HOC+ 1-->0 line with an intensity similar to that of the H13CO+ 1-->0 line. This implies an [HCO+]/[HOC+] ratio of ~40. These results corroborate the existence of a giant photodissociation region (PDR) in the nucleus of M82. In fact, the low [HCO+]/[HOC+] ratio can only be explained if the nucleus of M82 is formed by small (r<0.02-0.2 pc) and dense (n~a few times 104-105 cm-3) clouds immersed in an intense UV field (G0~104 in units of the Habing field). The detection of the hydrocarbons c-C3H2 and CH3C2H in the nucleus of M82 suggests that a complex carbon chemistry is developing in this giant PDR.
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