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arXiv · 2105.03735

[CII] $158\,\mu\mathrm{m}$ line emission from Orion A. I. A template for extragalactic studies?

C. H. M. Pabst·A. Hacar·J. R. Goicoechea·D. Teyssier·O. Berné·M. G. Wolfire·R. D. Higgins·E. T. Chambers·S. Kabanovic·R. Güsten·J. Stutzki·C. Kramer·A. G. G. M. Tielens
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Abstract

The [CII] $158\,\mu\mathrm{m}$ fine-structure line is one of the dominant coolants of the neutral interstellar medium. It is hence one of the brightest far-infrared emission lines and can be observed not only in star-forming regions throughout the Galaxy, but also in the diffuse interstellar medium and in distant galaxies. [CII] line emission has been suggested to be a powerful tracer of star-formation. We aim to understand the origin of [CII] emission and its relation to other tracers of interstellar gas and dust. This includes a study of the heating efficiency of interstellar gas as traced by the [CII] line to test models of gas heating. We make use of a one-square-degree map of velocity-resolved [CII] line emission towards the Orion Nebula complex, including M43 and NGC 1977. The [CII] intensity is tightly correlated with PAH emission in the IRAC $8\,\mu\mathrm{m}$ band and far-infrared emission from warm dust. The correlation between [CII] and CO(2-1) is affected by the detailed geometry of the region. We find particularly low [CII]-over-FIR intensity ratios towards large columns of (warm and cold) dust, which suggest the interpretation of the "[CII] deficit" in terms of a "FIR excess". A slight decrease in the FIR line-over-continuum intensity ratio can be attributed to a decreased heating efficiency of the gas. We find that, at the mapped spatial scales, predictions of the star-formation rate from [CII] emission underestimate the star-formation rate calculated from YSO counts in the Orion Nebula complex by an order of magnitude. [CII] emission from the Orion Nebula complex arises dominantly in the cloud surfaces, many viewed in edge-on geometry. [CII] emission from extended faint cloud surfaces may contribute significantly to the total [CII] emission on galactic scales.

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C. H. M. Pabst, A. Hacar, J. R. Goicoechea, D. Teyssier, O. Berné, M. G. Wolfire, R. D. Higgins, E. T. Chambers, S. Kabanovic, R. Güsten, J. Stutzki, C. Kramer, A. G. G. M. Tielens. 2021-05-08. [CII] $158\,\mu\mathrm{m}$ line emission from Orion A. I. A template for extragalactic studies?. https://doi.org/10.1051/0004-6361%2F202140804

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