Contributed Talk - Splinter ISM

Wednesday, 23 September 2020, 17:06   (virtual room F)

N-PDFs of molecular clouds in observations and simulations

N. Schneider and GENESIS consortium
I. Physik. Institut, University of Cologne

The main physical processes that govern the formation of molecular clouds and stars are turbulence, gravity, magnetic fields, and radiative feedback. Many analytic tools (PDFs, power spectra, structure functions, etc.) exist that help to trace and disentangle these various processes in observations and numerical simulations. The objective of the GENESIS (http://www.astro.uni-koeln.de/node/965) project is to apply such tools on dust and molecular line data sets of the Milky way to make progress in understanding the molecular cloud and star-formation process in our galaxy. I will here present the latest results from a study using N-PDFs (probability distribution functions of column-density) and the Delta-variance, applied to high resolution Herschel dust column density maps. A large range of clouds is covered, from diffuse regions up to massive star-forming complexes. We find that N-PDFs are best described by a log-normal distribution at low column densities and one or two power-law tails (PLTs) at high column densities. The second PLT is flatter (massive clouds) or steeper (mostly low-mass clouds) than the first PLT, and I will suggest various processes for that finding. The log-normal part is well traced and not a result from observational biases, as previously suggested. We also suceeded in identifying the HI-H2 transition in diffuse clouds using N-PDFs.