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The Evolution of Giant Molecular Clouds (GMCs) Driven by Galactic Spiral Arms in the Whirlpool Galaxy M51

Research team lead by Jin Koda at Stony Brook University (New York, USA) and Tsuyoshi Sawada at the National Astronomical Observatory of Japan discovered that the evolution of giant molecular clouds (GMCs) is driven by galactic spiral arms in the Whirlpool galaxy M51. Star formation occurs in GMCs, and an understanding of the evolution of GMCs is a prerequisite to develop theories of star formation and galaxy evolution. The team found that GMCs grow by collisional coagulation, and are ripped apart by gravitational potential gradients across spiral arms. The remnants of the broken-up GMCs are also found in the observations. The research became possible with the recent developments of an array receiver at the Nobeyama Radio Observatory and new millimeter-wave interferometer at the Combined Array for Research in Millimeter Astronomy Observatory (California, USA). The team combined the data from those state-of-the-art instruments. (Koda et al. 2009, ApJL, 700, 132)

Distribution of molecular gas (Giant Molecular Clouds - GMCs) in the Whirlpool galaxy M51