H$_2$ formation on interstellar dust grains: the viewpoints of theory, experiments, models and observations

Valentine Wakelam, Emeric Bron, Stephanie Cazaux, Francois Dulieu, Cécile Gry, Pierre Guillard, Emilie Habart, Liv Hornekær, Sabine Morisset, Gunnar Nyman, Valerio Pirronello, Stephen D. Price, Valeska Valdivia, Gianfranco Vidali, Naoki Watanabe

Published 2017-11-28Version 1

Molecular hydrogen is the most abundant molecule in the universe. It is the first one to form and survive photo-dissociation in tenuous environments. Its formation involves catalytic reactions on the surface of interstellar grains. The micro-physics of the formation process has been investigated intensively in the last 20 years, in parallel of new astrophysical observational and modeling progresses. In the perspectives of the probable revolution brought by the future satellite JWST, this article has been written to present what we think we know about the H$_2$ formation in a variety of interstellar environments.