A Comparative Study of Giant Molecular Clouds in M51, M33, and the Large Magellanic Cloud

摘要: We compare the properties of giant molecular clouds (GMCs) in M51 identified by Plateau de Bure Interferometer Whirlpool Arcsecond Survey with GMCs wide-field, high-resolution surveys CO emission M33 and Large Magellanic Cloud (LMC). find that are larger, brighter, have higher velocity dispersions relative to their sizes than equivalent structures LMC. These differences imply there genuine variations average mass surface density different GMC populations. To explain this, we propose pressure interstellar medium surrounding plays a role regulating dispersion. no evidence for correlation between size linewidth M51, M33, or LMC when is decomposed into GMCs, although moderately robust correlations apparent regions contiguous (with limitation) used. Our work demonstrates observational bias remains an important obstacle identification study extragalactic populations using emission, especially molecule-rich galactic environments.