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NRO legacy project: M 33 all disk survey of Giant Molecular Clouds (GMCs) with NRO-45m and ASTE-10m telescopes
Published online by Cambridge University Press: 25 November 2011
Abstract
We present the results of the Nobeyama Radio Observatory (NRO) M 33 All Disk (30′ × 30′, or 7.3 kpc × 7.3 kpc) Survey of Giant Molecular Clouds (NRO MAGiC) based on 12CO(J = 1–0) observations using the NRO 45-m telescope and 12CO(J = 3–2) observations using the ASTE 10-m telescope. The spatial resolution of the resultant 12CO(J = 1–0) map is 193, corresponding to 81 pc, which is sufficient to identify each Giant Molecular Cloud (GMC) in the disk. We found clumpy structures with a typical spatial scale of ~100 pc, corresponding to GMCs, and no diffuse, smoothly distributed component of molecular gas at this sensitivity.
We obtained a map of the molecular fraction, fmol = ΣH2/(ΣHi + ΣH2), at a 100-pc resolution. This is the first fmol map covering an entire galaxy with a GMC-scale resolution. The correlation between fmol and gas surface density shows two distinct sequences. The presence of two correlation sequences can be explained by differences in metallicity, i.e., higher (~2-fold) metallicity in the central region (r < 1.5 kpc) than in the outer parts. Alternatively, differences in scale height can also account for the two sequences, i.e., increased scale height toward the outer disk.
- Type
- Research Article
- Information
- European Astronomical Society Publications Series , Volume 52: Conditions and Impact of Star Formation , 2011 , pp. 125 - 128
- Copyright
- © EAS, EDP Sciences 2011