MOLECULAR GAS AND STAR-FORMATION PROPERTIES IN THE CENTRAL AND BAR REGIONS OF NGC 6946
- Department of Physics, Hokkaido University, Kita 10, Nishi 8, Kita-ku, Sapporo, Hokkaido 060-0810 (Japan)
- Division of Physics, Faculty of Pure and Applied Sciences, University of Tsukuba, Tennodai, Tsukuba, Ibaraki 305-8571 (Japan)
- Department of Physics and Astronomy, Stony Brook University, Stony Brook, NY 11794-3800 (United States)
- Joint ALMA Observatory, Alonso de Cordova 3107, Vitacura, Santiago (Chile)
- Nobeyama Radio Observatory, NAOJ, Minamimaki, Minamisaku, Nagano 384-1305 (Japan)
In this work, we investigate the molecular gas and star-formation properties in the barred spiral galaxy NGC 6946 using multiple molecular lines and star-formation tracers. A high-resolution image (100 pc) of {sup 13}CO (1–0) is created for the inner 2 kpc disk by the single-dish Nobeyama Radio Observatory 45 m telescope and interferometer Combined Array for Research in Millimeter-wave Astronomy, including the central region (nuclear ring and bar) and the offset ridges of the primary bar. Single-dish HCN (1–0) observations were also made to constrain the amount of dense gas. The physical properties of molecular gas are inferred from (1) the large velocity gradient calculations using our observations and archival {sup 12}CO (1–0), {sup 12}CO(2–1) data, (2) the dense gas fraction suggested by the luminosity ratio of HCN to {sup 12}CO (1–0), and (3) the infrared color. The results show that the molecular gas in the central region is warmer and denser than that of the offset ridges. The dense gas fraction of the central region is similar to that of luminous infrared galaxies/ultraluminous infrared galaxies, whereas the offset ridges are close to the global average of normal galaxies. The coolest and least-dense region is found in a spiral-like structure, which was misunderstood to be part of the southern primary bar in previous low-resolution observations. The star-formation efficiency (SFE) changes by about five times in the inner disk. The variation of SFE agrees with the prediction in terms of star formation regulated by the galactic bar. We find a consistency between the star-forming region and the temperature inferred by the infrared color, suggesting that the distribution of subkiloparsec-scale temperature is driven by star formation.
- OSTI ID:
- 22521783
- Journal Information:
- Astrophysical Journal, Vol. 815, Issue 1; Other Information: Country of input: International Atomic Energy Agency (IAEA); ISSN 0004-637X
- Country of Publication:
- United States
- Language:
- English
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