Bigiel, F., de Looze, I, Krabbe, A., Cormier, D., Barnes, A. T., Fischer, C., Bolatto, A. D., Bryant, A., Colditz, S., Geis, N., Herrera-Camus, R., Iserlohe, C., Klein, R., Leroy, A. K., Linz, H., Looney, L. W., Madden, S. C., Poglitsch, A., Stutzki, J. and Vacca, W. D. (2020). SOFIA/FIFI-LS Full-disk [C II] Mapping and CO-dark Molecular Gas across the Nearby Spiral Galaxy NGC 6946. Astrophys. J., 903 (1). BRISTOL: IOP PUBLISHING LTD. ISSN 1538-4357

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Abstract

We present SOFIA/FIFI-LS observations of the [C II] 158 mu m cooling line across the nearby spiral galaxy NGC 6946. We combine these with UV, IR, CO, and H I data to compare [C II] emission to dust properties, star formation rate (SFR), H-2, and H I at 560 pc scales via stacking by environment (spiral arms, interarm, and center), radial profiles, and individual, beam-sized measurements. We attribute 73% of the [C II] luminosity to arms, and 19% and 8% to the center and interarm region, respectively. [C II]/TIR, [C II]/CO, and [C II]/PAH radial profiles are largely constant, but rise at large radii (greater than or similar to 8 kpc) and drop in the center ([C II] deficit). This increase at large radii and the observed decline with the 70 mu m/100 mu m dust color are likely driven by radiation field hardness. We find a near proportional [C II]-SFR scaling relation for beam-sized regions, though the exact scaling depends on methodology. [C II] also becomes increasingly luminous relative to CO at low SFR (interarm or large radii), likely indicating more efficient photodissociation of CO and emphasizing the importance of [C II] as an H-2 and SFR tracer in such regimes. Finally, based on the observed [C II] and CO radial profiles and different models, we find alpha(CO) to increase with radius, in line with the observed metallicity gradient. The low alpha(CO) (galaxy average less than or similar to 2 M pc(-2) (K km s(-1))(-1)) and low [C II]/CO ratios (similar to 400 on average) imply little CO-dark gas across NGC 6946, in contrast to estimates in the Milky Way.

Item Type: Journal Article
Creators:
CreatorsEmailORCIDORCID Put Code
Bigiel, F.UNSPECIFIEDUNSPECIFIEDUNSPECIFIED
de Looze, IUNSPECIFIEDUNSPECIFIEDUNSPECIFIED
Krabbe, A.UNSPECIFIEDUNSPECIFIEDUNSPECIFIED
Cormier, D.UNSPECIFIEDUNSPECIFIEDUNSPECIFIED
Barnes, A. T.UNSPECIFIEDUNSPECIFIEDUNSPECIFIED
Fischer, C.UNSPECIFIEDUNSPECIFIEDUNSPECIFIED
Bolatto, A. D.UNSPECIFIEDUNSPECIFIEDUNSPECIFIED
Bryant, A.UNSPECIFIEDUNSPECIFIEDUNSPECIFIED
Colditz, S.UNSPECIFIEDUNSPECIFIEDUNSPECIFIED
Geis, N.UNSPECIFIEDUNSPECIFIEDUNSPECIFIED
Herrera-Camus, R.UNSPECIFIEDUNSPECIFIEDUNSPECIFIED
Iserlohe, C.UNSPECIFIEDUNSPECIFIEDUNSPECIFIED
Klein, R.UNSPECIFIEDUNSPECIFIEDUNSPECIFIED
Leroy, A. K.UNSPECIFIEDUNSPECIFIEDUNSPECIFIED
Linz, H.UNSPECIFIEDUNSPECIFIEDUNSPECIFIED
Looney, L. W.UNSPECIFIEDUNSPECIFIEDUNSPECIFIED
Madden, S. C.UNSPECIFIEDUNSPECIFIEDUNSPECIFIED
Poglitsch, A.UNSPECIFIEDUNSPECIFIEDUNSPECIFIED
Stutzki, J.UNSPECIFIEDUNSPECIFIEDUNSPECIFIED
Vacca, W. D.UNSPECIFIEDUNSPECIFIEDUNSPECIFIED
URN: urn:nbn:de:hbz:38-313715
DOI: 10.3847/1538-4357/abb677
Journal or Publication Title: Astrophys. J.
Volume: 903
Number: 1
Date: 2020
Publisher: IOP PUBLISHING LTD
Place of Publication: BRISTOL
ISSN: 1538-4357
Language: English
Faculty: Unspecified
Divisions: Unspecified
Subjects: no entry
Uncontrolled Keywords:
KeywordsLanguage
STAR-FORMATION; RADIAL-DISTRIBUTION; MILKY-WAY; LINE; SINGS; DUST; INDICATOR; CLOUDS; HIMultiple languages
Astronomy & AstrophysicsMultiple languages
URI: http://kups.ub.uni-koeln.de/id/eprint/31371

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