Abstract
We present computations of [CI] 609 μm and 370 μm fine-structure line emission from non-equilibrium clouds which are suddenly shielded from initially intense far-ultraviolet radiation fields. After the incident UV fluxes are diminished the initially abundant C+ ions rapidly recombine, and the neutral atomic carbon is then slowly incorporated into CO molecules. The cloud cooling times are longer than the CI formation times, and intense [CI] emission persists as the clouds cool. The [CI] emission is thus much brighter from cooling clouds than in equilibrium photon dominated regions. We argue that if UV-scattering is inefficient the extended [CI] emission observed in star-forming regions may be better explained by nonequilibrium models than by steady state models.
Original language | English |
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Pages (from-to) | L13-L16 |
Journal | Astronomy and Astrophysics |
Volume | 323 |
Issue number | 1 |
State | Published - 1 Jul 1997 |
Keywords
- ISM: clouds
- ISM: molecules
- Line: formation
- Radio lines: interstellar