Details

Autor(en) / Beteiligte

• Bigiel, F.
• Looze, I. de
• 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.
• Vacca, W. D.

Titel

SOFIA/FIFI-LS Full-disk [C ii] Mapping and CO-dark Molecular Gas across the Nearby Spiral Galaxy NGC 6946

Ist Teil von

• The Astrophysical journal, 2020-11, Vol.903 (1), p.30

Ort / Verlag

Philadelphia: The American Astronomical Society

Erscheinungsjahr

2020

Quelle

EZB Electronic Journals Library

Beschreibungen/Notizen

• We present SOFIA/FIFI-LS observations of the [C ii] 158 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), H2, 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 (  8 kpc) and drop in the center ("[C ii] deficit"). This increase at large radii and the observed decline with the 70  m/100 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 H2 and SFR tracer in such regimes. Finally, based on the observed [C ii] and CO radial profiles and different models, we find CO to increase with radius, in line with the observed metallicity gradient. The low CO (galaxy average  2 M pc−2 (K km s−1)−1) and low [C ii]/CO ratios (∼400 on average) imply little CO-dark gas across NGC 6946, in contrast to estimates in the Milky Way.