An Updated View of Giant Molecular Clouds, Gas Flows and Star Formation in M51 with PAWS (original) (raw)

We present an overview of the latest results from the PdBI Arcsecond Whirlpool Survey (PAWS, PI: E. Schinnerer), which has mapped CO(1-0) emission in the nearby granddesign spiral galaxy M51 at 40pc resolution. Our data are sensitive to GMCs above 10 5 M , allowing the construction of the largest GMC catalog to date-containing over 1500 objectsusing the CPROPS algorithm (Rosolowsky & Leroy 2006). In the inner disk of M51, the properties of the CO emission show significant variation that can be linked to the dynamical environment in which the molecular gas is located. We find that dynamically distinct regions host clouds with different properties and exhibit different GMC mass spectra, as well as distinct patterns of star formation. To understand how this sensitivity to environment emerges, we consider the role of pressure on GMC stabilization (including shear and star formation feedback-driven turbulence). We suggest that, in the presence of significant external pressure, streaming motions driven by the spiral arm can act to reduce the surface pressure on clouds. The resulting stabilization impacts the global pattern of star formation and can account for the observed nonmonotonic radial dependence of the gas depletion time. Our findings have implications for the observed scatter in the standard GMC relations and extragalactic star formation laws.