Dirty Window

This book offers an excellent introduction to the physics of molecular gas in the Galaxy. It deals with the diffuse interstellar medium which provides an interesting environment for exploring the neutral gas content of a galaxy like the Milky Way and the techniques necessary for studying this non-stellar component. After an initial exposition of the phases of the interstellar medium and the role of gas in a spiral galaxy, the authors discuss the transition from atomic to molecular gas. They then consider basic radiative transfer and molecular spectroscopy with particular emphasis on the molecules useful for studying low-density molecular gas. Observational techniques for investigating the gas and the dust component of the diffuse interstellar medium throughout the electromagnetic spectrum are explored emphasizing results from the recent Herschel and Planck missions. A brief exposition of some of the theoretical techniques for studying gas in the Galaxy is followed by a discussion of how these techniques are applied to molecular clouds in general and high-latitude clouds in particular. The high-latitude molecular clouds are examined in detail as vehicles for applying the techniques developed in the book. The role of turbulence in the origin and dynamics of high-latitude clouds is discussed and the impact of these low-extinction molecular clouds on extragalactic studies is examined. The book is targeted at graduate students or postdocs who are entering the field of interstellar medium studies.