EPoS Contribution
EPoS Contribution
Demographics of Molecular Cloud Evolution

Peter Barnes
U Florida, Gainesville, US
New multi-line mapping surveys of molecular clouds (CHaMP, ThrUMMS, SEDIGISM), are enabling an unprecedented demographic analysis of the physics of entire cloud populations. Key insights from such surveys include("he1.php"); of subthermally excited, massive dense clumps, the majority of which are not engaged in vigorous star formation, but are pressure-stabilised aginst dispersal by their overlying envelopes, implying long (several x 107 yr) cloud lifetmes; (2) A new CO -> H2 conversion law accounting for these numerous pc-scale, low-excitation, high-opacity and high column density clumps, suggesting the total molecular mass of clouds from pc to kpc scales may be underestimated by a factor of 2-3, and increasing the gas depletion timescale by the same factor; (3) Widespread, slow inflow of material into cloud complexes on ~10 pc scales, which suggests that the 40-yr old question of whether molecular line velocity dispersions are gravity- or turbulence-dominated on these scales, may be resolved in favour of gravity in most locations. We summarise these results and discuss implications for our understanding of star formation and the life cycle of molecular clouds.
E. Muller, NAOJ, JP
A. Hernandez, U Wisconsin, US
Key publication

Suggested Session: Molecular Clouds