Cold Dark Clouds: The Initial Conditions for Star Formation

TL;DR

This review summarizes recent advances in understanding cold dark clouds, their filamentary structures, turbulence, and starless cores, which are crucial for comprehending the initial conditions of star formation.

Contribution

It highlights new observations of infrared dark clouds and detailed studies of starless cores, advancing knowledge of the physical and chemical conditions before star formation.

Findings

Dark clouds exhibit filamentary mass distributions with supersonic turbulence.

Starless cores show simple physical properties but complex chemical structures.

Molecular freeze-out onto dust grains influences core chemistry.

Abstract

Cold dark clouds are nearby members of the densest and coldest phase in the galactic interstellar medium, and represent the most accessible sites where stars like our Sun are currently being born. In this review we discuss recent progress in their study, including the newly discovered infrared dark clouds that are likely precursors to stellar clusters. At large scales, dark clouds present filamentary mass distributions with motions dominated by supersonic turbulence. At small, sub-parsec scales, a population of subsonic starless cores provides a unique glimpse of the conditions prior to stellar birth. Recent studies of starless cores reveal a combination of simple physical properties together with a complex chemical structure dominated by the freeze-out of molecules onto cold dust grains. Elucidating this combined structure is both an observational and theoretical challenge whose solution will bring us closer to understanding how molecular gas condenses to form stars.