Search

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 grand-design spiral galaxy M51 at 40pc resolution. Our data are sensitive to GMCs above 105 M⊙, allowing the construction of the largest GMC catalog to date – containing over 1500 objects – using 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 non-monotonic 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. [ABSTRACT FROM PUBLISHER]

We study the feeding and feedback of the nucleus of M51 by considering gravitational torques, responsible for gas inflow, in relation to the local distribution of dense gas. [ABSTRACT FROM PUBLISHER]

The lifetime of the structure in grand design spiral galaxies is observationally ill-determined, but is essentially set by how accurately the rotation of the pattern can be characterized by a single angular pattern speed. This paper derives a generalized version of the Tremaine–Weinberg method for observationally determining pattern speeds, in which the pattern speed is allowed to vary arbitrarily with radius. The departures of the derived pattern speed from a constant then provide a simple metric of the lifetime of the spiral structure. Application of this method to CO observations of NGC 1068 reveals that the pattern speed of the spiral structure in this galaxy varies rapidly with radius, and that the lifetime of the spiral structure is correspondingly very short. If this result turns out to be common in grand-design spiral galaxies, then these features will have to be viewed as highly transient phenomena. [ABSTRACT FROM AUTHOR]