Copenhagen Astrophysics Seminars (CAS): Peter Laursen - Lyman α — a window to the distant Universe

Abstract:

Lyman α is the most common type of light emitted from the most common element in the Universe, and is hence used to study galaxies across the entire Universe. Being sensitive to many different physical processes — such as gas temperature, dust contents, galactic outflows, and intergalactic ionization state — it is simultaneously extremely informative and notoriously hard to interpret.

Most of the Lyman α emitted from galaxies is related to newly formed stars, but a significant fraction is expected to be emitted from gas feeding the galaxies from the surrounding intergalactic medium, cooling as it plummets down the potential well of the galaxy. Whereas the former is observed regularly, detection of the latter is challenging, and as yet evidence for its existence is at best tentative.

In this seminar I will review the wonders and pitfalls of Lyman α, and present work-in-progress analytical estimates of the amount of cooling radiation.