AA54CH09-McQuinn ARI 29 August 2016 8:37 ANNUAL REVIEWS Further Click here to view this article's online features: • Download figures as PPT slides • Navigate linked references • Download citations The Evolution of the • Explore related articles • Search keywords Intergalactic Medium Matthew McQuinn Department of Astronomy, University of Washington, Seattle, Washington 98195; email:
[email protected] Annu. Rev. Astron. Astrophys. 2016. 54:313–62 Keywords First published online as a Review in Advance on intergalactic medium, IGM, physical cosmology, large-scale structure, July 22, 2016 quasar absorption lines, reionization, Lyα forest The Annual Review of Astronomy and Astrophysics is online at astro.annualreviews.org Abstract This article’s doi: The bulk of cosmic matter resides in a dilute reservoir that fills the space be- 10.1146/annurev-astro-082214-122355 Access provided by California Institute of Technology on 01/11/17. For personal use only. tween galaxies, the intergalactic medium (IGM). The history of this reservoir Annu. Rev. Astron. Astrophys. 2016.54:313-362. Downloaded from www.annualreviews.org Copyright c 2016 by Annual Reviews. is intimately tied to the cosmic histories of structure formation, star forma- All rights reserved tion, and supermassive black hole accretion. Our models for the IGM at intermediate redshifts (2 z 5) are a tremendous success, quantitatively explaining the statistics of Lyα absorption of intergalactic hydrogen. How- ever, at both lower and higher redshifts (and around galaxies) much is still unknown about the IGM. We review the theoretical models and measure- ments that form the basis for the modern understanding of the IGM, and we discuss unsolved puzzles (ranging from the largely unconstrained process of reionization at high z to the missing baryon problem at low z), highlighting the efforts that have the potential to solve them.