Photon-dominated Chemistry in the Nucleus of M82: Widespread HOC+ Emission in the Inner 650 Parsec Disk

Asunción Fuente (1) , Santiago García-Burillo (1) , Maryvonne Gerin (2, 3) , David Teyssier (4) , Antonio Usero (1) , J. R. Rizzo (1) , P. de Vicente (1)

1 Observatorio Astronomico Nacional, Madrid
2 LERMA - Laboratoire d'Etude du Rayonnement et de la Matière en Astrophysique
3 Dynamique des milieux interstellaires et plasmas stellaires
4 Space Research Organization of the Netherlands

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

Domaines: Astrophysique [astro-ph]

Asunción Fuente, Santiago García-Burillo, Maryvonne Gerin, David Teyssier, Antonio Usero, et al.. Photon-dominated Chemistry in the Nucleus of M82: Widespread HOC+ Emission in the Inner 650 Parsec Disk. The Astrophysical journal letters, 2005, 619, pp.L155-L158. ⟨10.1086/427990⟩. ⟨hal-03743030⟩