Hunting for dark matter in the forest

Tom Theuns, Durham University

Gas in between galaxies produces a forest of absorption lines in the spectra of bright objects such as distant quasars. This "Lyman-alpha forest" arises due to absorption by a sprinkling of neutral hydrogen in the otherwise highly ionised intergalactic gas, with many  lines forming in mildly over dense, or indeed under dense intervening structures. These modest fluctuations can be simulated quite accurately, and comparing mock spectra to the exquisitely high resolution and high signal-to-noise observed spectra allows tight constraints on the nature of the absorbers.

In this talk, I will concentrate on what such as comparison tells up about the temperature and ionisation state of the gas, and explain how these measurements can also put tight constraints on any free streaming due to warm dark matter.

(The slides will be available here)