Observational studies of pre-stellar cores and infrared dark clouds

TL;DR

This paper reviews observational and theoretical studies of pre-stellar cores and infrared dark clouds, highlighting their physical and chemical properties, and discussing open questions in star formation research.

Contribution

It provides a comprehensive overview of recent advances in understanding PSCs and IRDCs, emphasizing the role of observations and models in unveiling star formation conditions.

Findings

PSCs are cold and quiescent with molecular freeze-out effects.

Deuterated molecules are key tracers of PSC structure.

Ongoing research aims to understand massive PSCs in IRDCs.

Abstract

Stars like our Sun and planets like our Earth form in dense regions within interstellar molecular clouds, called pre-stellar cores (PSCs). PSCs provide the initial conditions in the process of star and planet formation. In the past 15 years, detailed observations of (low-mass) PSCs in nearby molecular cloud complexes have allowed us to find that they are cold (T < 10 K) and quiescent (molecular line widths are close to thermal), with a chemistry profoundly affected by molecular freeze-out onto dust grains. In these conditions, deuterated molecules flourish, becoming the best tools to unveil the PSC physical and chemical structure. Despite their apparent simplicity, PSCs still offer puzzles to solve and they are far from being completely understood. For example, what is happening to the gas and dust in their nuclei (the future stellar cradles) is still a mystery that awaits for ALMA. Other important questions are: how do different environments and external conditions affect the PSC physical/chemical structure? Are PSCs in high-mass star forming regions similar to the well-known low-mass PSCs? Here I review observational and theoretical work on PSCs in nearby molecular cloud complexes and the ongoing search and study of massive PSCs embedded in infrared dark clouds (IRDCs), which host the initial conditions for stellar cluster and high-mass star formation.