I saw that the link in the OP was posted over eleven years ago so I looked a little deeper and found this; 'Chandra's First Decade of Discovery Special Feature Supermassive Black-hole Growth Over Cosmic Time: Active galaxy demography, physics, and ecology from Chandra surveys'. . http://ncbi.nlm.nih.gov/pmc/articles/PMC2867739/ . . My link may not work. If so you can google its' 'Title' (found in the first paragraph of this post) and, if you could, post the proper link. Thank you.