2018/02/26 by Dragan Salak, Yuto Tomiyasu, Naomasa Nakai +3 · 1 citation
Physics and Astronomy · #Astrophysics and Star Formation Studies #Electron temperature #Excitation #Excitation temperature #Galaxies: Formation, Evolution, Phenomena #Galaxy #Intensity (physics) #Line (geometry) #Molecular cloud #Outflow #RADIUS #Star formation #Stellar, planetary, and galactic studies #astro-ph.GA
paper · pdf · doi:10.3847/1538-4357/aab2ac
Accepted for publication in ApJ
arxiv created 2018/02/26 · openalex created_date 2018/03/06 · openalex publication_date 2018/03/28 · arxiv updated 2018/04/11 · openalex updated_date 2026/08/05
Abstract Dense molecular gas tracers in the central 1 kpc region of the superwind galaxy NGC 1808 have been imaged by ALMA at a resolution of 1″ (∼50 pc). Integrated intensities and line intensity ratios of HCN (1–0), H 13 CN (1–0), HCO + (1–0), H 13 CO + (1–0), HOC + (1–0), HCO + (4–3), CS (2–1), C 2 H (1–0), and previously detected CO (1–0) and CO (3–2) are presented. SiO (2–1) and HNCO (4–3) are detected toward the circumnuclear disk (CND), indicating the presence of shocked dense gas. There is evidence that an enhanced intensity ratio of HCN (1–0)/HCO + (1–0) reflects star formation activity, possibly in terms of shock heating and electron excitation in the CND and a star-forming ring at radius ∼300 pc. A non-local thermodynamic equilibrium analysis indicates that the molecular gas traced by HCN, H 13 CN, HCO + , and H 13 CO + in the CND is dense ( ) and warm (20 K ≲ T k ≲ 100 K). The calculations yield a low average gas density of for a temperature of in the nuclear outflow. Dense gas tracers HCN (1–0), HCO + (1–0), CS (2–1), and C 2 H (1–0) are detected for the first time in the superwind of NGC 1808, confirming the presence of a velocity gradient in the outflow direction.