The Structured Interstellar Medium: Infrared-dark clouds from Herschel to ALMA

• Applicant: Sarah E. Ragan, Ph.D.
• Subject Area: Astrophysics and Astronomy
• Term: from 2011 to 2014
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 203354420

Molecular gas makes up the smallest volume fraction of the phases of the interstellar medium (ISM), yet it is of paramount importance in the formation of stars. The densest condensations in molecular clouds are confined to filamentary structures in the Galactic plane; the most striking of these structures are infrared-dark clouds (IRDCs), which reside in the spiral arms where the molecular gas distribution in the Milky Way peaks. IRDCs are thought to be the birthplaces of rich star clusters. Star formation in IRDCs is poorly constrained because light from embedded protostars is heavily obscured by dust. For the first time, Herschel now provides high-resolution access to the far-infrared, where the extinction by dust lessens. This proposal aims to connect the small structures seen by Herschel to large-scale filaments in order to understand the conditions under which IRDCs fragment and ultimately form stars using Herschel, Spitzer, and millimeter (line and continuum) observations of a well-studied sample of IRDCs. We will also conduct a survey of high-resolution molecular line maps using the Plateau de Bure Interferometer and ALMA that will help constrain the kinematics in IRDCs at various stages of their fragmentation. This suite of observations will test predictions of molecular cloud simulations using radiative transfer modeling. By providing powerful observational constraints on models of IRDCs, this project serves as a bedrock for forming a coherent model of the densest phase of the ISM.

• DFG Programme: Priority Programmes
• Subproject of: SPP 1573: Physics of the Interstellar Medium