EPoS Contribution
EPoS Contribution
Unfolding the Laws of Star Formation: The Density Distribution of Molecular Clouds

Jouni Kainulainen
MPIA, Heidelberg, DE
The rate and efficiency of star formation in the interstellar medium (ISM) depend crucially on the density structure of individual molecular clouds. This structure is most decisively encapsulated in the probability density function of volume densities (rho-PDF) in molecular clouds, which directly determines the star formation rates predicted by analytic models. Contrasting its fundamental role in the models, the rho-PDF function has remained observationally unconstrained. This is because observations can only probe projected column densities, not volume densities. In this contribution, I describe a new approach that allows us to estimate the rho-PDFs of molecular clouds using column density data. We apply the approach to the Solar neighbourhood clouds and perform the first systematic quantification of the molecular cloud rho-PDFs. We then connect the derived rho-PDFs to the star formation rates and efficiencies of the clouds. We show that the rho-PDFs give rise to a volume density threshold of star formation and we quantify the star formation efficiency above the threshold. This approach allows us to correctly predict several key properties of the star-forming ISM, such as the total star-formation rate of the Solar neighbourhood clouds and of the entire Milky Way. The results show that the volume density structure of molecular clouds, as measured by the rho-PDFs, is indeed one fundamental element in determining the star-forming capability of the ISM.
Collaborators:
C. Federrath, Monash U, Australia
T. Henning, MPIA, DE
Key publication

Suggested Sessions: Molecular Clouds