Exposing the plural nature of molecular clouds

Séminaire IPAG de Jean-François Robitaille (IPAG), jeudi 21 novembre 2019 à 11h00, IPAG seminar room

Understanding the physics of the star formation process in molecular clouds is one of the most fundamental ambitions of modern astrophysics. Through these physical processes the interstellar gas phase changes, forming dense coherent structures. Historically, most research in this area was focused on two strategies : describing the local peaks of emission associated with the filamentary structures or the star-forming cores, or analysing statistically the global gas distribution of star-forming regions. Unfortunately, the essential connection between dense structures and their environment has been overlooked.

In this seminar, I will describe multiscale approaches that can be used to analyse various astrophysical data in order to understand the connection between these two components. Such analysis techniques can be applied on column-density maps, velocity fields, polarisation data and more. Based on the formalism of wavelet transforms, these approaches allow us to disentangle the true scale-free (fractal nature) of molecular clouds from the dense coherent filamentary structure, locate the intermittent behaviour (multifractal nature) of turbulent velocity fields and analyse the perturbations of regular magnetic fields. I will talk about the formalism as well as the physical and statistical arguments behind such decompositions.