Research: Interstellar Medium

Studies of the interstellar medium (ISM) address the diffuse gas and dust between stars, and their role in the life cycles of stars and of galaxies. Derived from the infall of gas from intergalactic space, the ISM is the substrate from which stars condense and into which stellar winds and supernovae expand. All aspects of galactic evolution -- the way galaxies appear from afar, the rate at which they form stars of various types, and the manner in which they intensify their internal magnetic fields -- are manifestations of how the ISM reacts to internal forces (e.g., supernovae) and to external forces (e.g., collisions between galaxies). Despite fifty years of progress, many open questions remain: for instance, how do newborn stars affect the gas clouds from which they formed? What is the mechanism by which dust grains align with the magnetic field? How can this effect be used to interpret observations of dense, cold molecular clouds? What are the basic dynamics and structure of these objects, from which stars form? CITAzens have been addressing these questions with techniques ranging from fundamental physics, to analytical and numerical modeling of important phenomena, to the detailed investigation of individual regions, as outlined below.

Significant activities related to the analysis of the Planck data is underway, involving P. G. Martin, M.-A. Miville-Deschenes, D. Goncalves and K. Blagrave. 25 papers describing the first set of Planck results were submitted in Jan 2011. CITA was leading one paper on interstellar dust in the local interstellar medium and the Galactic halo.

The Planck results are tightly related to a large 21 cm observation program at the Green Bank Telescope led by P. G. Martin. These observations of the atomic gas covers more than 800 square degrees at high Galactic latitude. The analysis of this exceptionnal data set is on-going, especially in the context of a study of the HI thermal instability (transition between the warm and cold phase) and its role in the formation of cold and dense structure in the ISM.

Relates to that, a new project on numerical simulations of turbulent and thermally bi-stable gas has started at CITA with the thesis of Eleonore Saury (student of M.-A. Miville-Deschenes). This simulation effort makes use of the SCINET facility. Two papers are in preparation.

A Herschel Open Time (OT1) project was accepted (M.-A. Miville-Deschenes P.I.) on the "First steps toward star formation: unveiling the atomic to molecular transition in the diffuse interstellar medium". Observations were obtained succesfully and the analysis is on-going.