Loris Magnani Libri

This book introduces the physics of interstellar gas in the Galaxy, focusing on the diffuse interstellar medium that provides a complex environment for studying the neutral gas content of galaxies like the Milky Way. It begins with an overview of the phases of the interstellar medium and the role of gas in spiral galaxies, followed by a discussion on the transition from atomic to molecular gas. The authors cover basic radiative transfer and molecular spectroscopy, emphasizing molecules relevant for low-density molecular gas studies. Observational techniques for exploring the gas and dust in the diffuse interstellar medium across the electromagnetic spectrum are examined, highlighting results from the Herschel and Planck missions. A concise discussion on dust in this medium precedes an exploration of molecular clouds, particularly high-latitude molecular clouds. The calibration of CO observations with molecular hydrogen content is addressed, along with the dark molecular gas controversy. High-latitude molecular clouds are analyzed as practical examples for applying the techniques discussed. The transient nature of diffuse and translucent molecular clouds is considered, with a detailed examination of turbulence's role in their origin and dynamics. This work is aimed at graduate students and postdocs entering the field of interstellar medium studies.