Observing Emission/Absorption Lines

In this 15 minute video,  Berkeley Astronomer Alan Parsons clearly and precisely describes the basics of how absorption/emission lines show up in the spectra measured by telescopes, and what these lines can tell us about astrophysical objects. Atomic cross sections and thermal boradening are described in detail., 

Optical Depth and Absorption

In this 90 minute in-depth lecture, astronomer Chris Churchill introduces the formalism of absorption lines and ionization edges. He covers optical depth (definition); opacity; cross sections; radiative excitation and ionization; mean free path; optical depth (interpretation); column density; thermal (Doppler) broadening; anatomy of absorption line Voigt profiles; equivalent width; curve of growth; and ionization edges (Lyman limit breaks).

QSO Absorption Lines: Intergalactic Medium and the Cosmic Web

In this 11 minute introduction, Caltech astronomer George Djorgovski explains the intergalactic medium as seen in quasar spectra, incuding what Lyman Limit (LLS) and damped Lyman-alpha (DLA)  absorbers look like in the spectra.  He also describes the equivalent width and the curve of growth. 

What is the Circumgalactic Medium?

A 50 minute "Blackboard Talk" by astrophyscists Romeel Davé explaining what the circumgalactic medium is -- or at least what we understand about it as of 2021.  This talk is a highly informative "rough and ready" exposition that also provides excellent background describing galaxies in the modern cosmological paradigm.

Fundamentals of Gaseous Halos

This Youtube Channel is a repository of videos from the Kavli Institute for Theoretical Physics (KITP) Program "Fundamentals of Gaseous Halos" helpd in Jan-Mar 2021.  This channel shares video recordings of all the program's daily activities, including keynote talks, discussion panels, and tutorials.  It also showcases user-submitted videos highlighting new results from the field of the circumgalactic medium (CGM).