STAR FORMATION ON SUBKILOPARSEC SCALE TRIGGERED BY NON-LINEAR PROCESSES IN NEARBY SPIRAL GALAXIES
- Department of Astronomy, University of Tokyo, Hongo, Bunkyo-ku, Tokyo 113-0033 (Japan)
- Department of Physics and Astronomy, Stony Brook University, Stony Brook, NY 11794-3800 (United States)
- Institute of Astronomy, University of Cambridge, Cambridge CB3 0HA (United Kingdom)
- Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency, Chuo-ku, Sagamihara, Kanagawa 252-5210 (Japan)
- Astronomy Department, University of Massachusetts, Amherst, MA 01003-9305 (United States)
- National Astronomical Observatory of Japan, Mitaka, Tokyo 181-8588 (Japan)
- Astronomy Department, California Institute of Technology, MC 249-17, 1200 East California Boulevard, Pasadena, CA 91125 (United States)
- Nobeyama Radio Observatory, National Astronomical Observatory of Japan, Nobeyama, Minamimaki, Minamisaku, Nagano 384-1305 (Japan)
We report a super-linear correlation for the star formation law based on new CO(J = 1-0) data from the CARMA and NOBEYAMA Nearby-galaxies (CANON) CO survey. The sample includes 10 nearby spiral galaxies, in which structures at sub-kpc scales are spatially resolved. Combined with the star formation rate surface density traced by H{alpha} and 24 {mu}m images, CO(J = 1-0) data provide a super-linear slope of N = 1.3. The slope becomes even steeper (N = 1.8) when the diffuse stellar and dust background emission is subtracted from the H{alpha} and 24 {mu}m images. In contrast to the recent results with CO(J = 2-1) that found a constant star formation efficiency (SFE) in many spiral galaxies, these results suggest that the SFE is not independent of environment, but increases with molecular gas surface density. We suggest that the excitation of CO(J = 2-1) is likely enhanced in the regions with higher star formation and does not linearly trace the molecular gas mass. In addition, the diffuse emission contaminates the SFE measurement most in regions where the star formation rate is law. These two effects can flatten the power-law correlation and produce the apparent linear slope. The super-linear slope from the CO(J = 1-0) analysis indicates that star formation is enhanced by non-linear processes in regions of high gas density, e.g., gravitational collapse and cloud-cloud collisions.
- OSTI ID:
- 22140335
- Journal Information:
- Astrophysical Journal Letters, Vol. 772, Issue 1; Other Information: Country of input: International Atomic Energy Agency (IAEA); ISSN 2041-8205
- Country of Publication:
- United States
- Language:
- English
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