A. Fuente and J. Martín-Pintado 1997 ApJ 477 L107 doi:10.1086/310532
A. Fuente1 and J. Martín-Pintado1
Show affiliationsWe have detected CO+ toward the photon-dominated region (PDR) associated with the reflection nebula NGC 7023. This is the first detection of CO+ in the vicinity of a Be star. A CO+ column density of 3 × 1011 cm-2 has been derived toward the PDR peak. However, we have not detected CO+ in a well-shielded clump of the adjacent molecular cloud, where the CO+/HCO+ abundance ratio is at least 100 times lower than in the PDR. Our results show, for the first time, that CO+ column densities as large as 3 × 1011 cm-2 can be produced in regions with incident UV fields of just a few 103 (in units of Habing field) and densities of ≤105 cm-3. Furthermore, since the ionization potential of CO is larger than 13.6 eV, our data rule out the direct photoionization of CO as a significant CO+ formation mechanism.
ISM: abundances; ISM: individual (NGC 7023); radio lines: ISM; reflection nebulae; stars: individual (HD 200775); stars: pre-main sequence
Issue 2 (1997 March 10)
Received 1996 October 24, accepted for publication 1996 December 11
A. Fuente and J. Martín-Pintado 1997 ApJ 477 L107
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