The Unchanging Circumgalactic Medium Over the Past 11 Billion Years
  This paper examines how the circumgalactic medium (CGM) evolves as a function of time by comparing results from different absorption-line surveys that have been conducted in the vicinities of galaxies at different redshifts. Despite very different star formation properties of the galaxies considered in these separate studies and different intergalactic radiation fields at redshifts between z~2.2 and z~0, I show that both the spatial extent and mean absorption equivalent width of the CGM around galaxies of comparable mass have changed little over this cosmic time interval. 
Hsiao-Wen Chen (U Chicago/KICP)
astro-ph.CO