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          Institute: MPI für Astronomie     Collection: Publikationen_mpia     Display Documents

ID: 742634.0, MPI für Astronomie / Publikationen_mpia
The survey of lines in M31 (SLIM): The drivers of the [C II]/TIR variation
Authors:Kapala, M. J.; Groves, B.; Sandstrom, K.; Jarrett, T.; da Cunha, E.; Croxall, K.; Dalcanton, J.; Draine, B.; Glover, S.; Schinnerer, E.
Date of Publication (YYYY-MM-DD):2017
Title of Journal:The Astrophysical Journal
Issue / Number:2
Start Page:id. 128 (19 pp)
Audience:Not Specified
Abstract / Description:The ratio of the [C II] 158 μ {{m}} emission line over the total infrared emission (TIR) is often used as a proxy for the photoelectric (PE) heating efficiency ({ɛ }{PE}) of the far-ultraviolet (FUV) photons absorbed by dust in the interstellar medium. In the nearby galaxy M31, we measure a strong radial variation of [C II]/TIR that we rule out as being due to an intrinsic variation in {ɛ }{PE}. [C II]/TIR fails as a proxy for {ɛ }{PE}, because the TIR measures all dust heating, not just the contribution from FUV photons capable of ejecting electrons from dust grains. Using extensive multi-wavelength coverage from the FUV to far-infrared, we infer the attenuated FUV emission ({{UV}}{att}), and the total attenuated flux ({{TOT}}{att}). We find [C II]/TIR to be strongly correlated with {{UV}}{att}/{{TOT}}{att}, indicating that, in M31 at least, one of the dominant drivers for [C II]/TIR variation is the relative hardness of the absorbed stellar radiation field. We define {ɛ }{PE}{UV}, [C II]/{{UV}}{att} which should be more closely related to the actual PE efficiency, which we find to be essentially constant (1.85+/- 0.8 % ) in all explored fields in M31. This suggests that part of the observed variation of [C II]/TIR in other galaxies is likely due to a change in the relative hardness of the absorbed stellar radiation field, caused by a combination of variations in the stellar population, dust opacity, and galaxy metallicity, though PE efficiency may also vary across a wider range of environments.
Free Keywords:dust; extinction; galaxies: ISM; galaxies: photometry; ISM: lines and bands; methods: data analysis; techniques: imaging spectroscopy
External Publication Status:published
Document Type:Article
Communicated by:N. N.
Affiliations:MPI für Astronomie
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