Dust Evolution from the Perspective of Nearby Galaxies
Intervenant : Frédéric Galliano
AIM, CEA/Saclay, France
A precise characterization of the grain properties is crucial for understanding the life cycle of the interstellar medium (ISM) and the evolution of galaxies. Nowadays, most of our knowledge of dust physics comes from studies of the Milky Way (MW). However, an increasing number of results on nearby galaxies provide unique discriminating constraints on fundamental grain processes. Indeed, nearby galaxies harbor a wider diversity of environmental conditions (metallicity, star-formation activity, etc.) than can be found in the MW. In particular, these nearby systems allow us to observe dust in extreme conditions, providing us valuable empirical information on grain evolution. They also constitute a necessary intermediate step toward understanding distant galaxies, as they are spatially resolved and have better wavelength coverage.
I will start with a general introduction, presenting the challenges in dust physics, and the recent advances in our understanding of the grain properties of the nearby Universe. I will then review several studies of the DustPedia project. This european collaboration aims to build a reference survey of ≈900 nearby, NIR-selected galaxies, observed with Herschel. I will detail the effort in modelling techniques we have carried out to provide the most accurate analysis possible of our data. I will finally present the various scaling relations and dust evolution trends derived among and within galaxies. I will discuss, in particular, the evolution of the dust-to-gas mass ratio and the fraction of aromatic feature carriers as a function of metallicity and star formation activity.