X-rays from the High-Redshift Universe: The Chandra view
  The study of the X-ray properties of z>4 quasars has grown substantially over the last few years, mostly thanks to Chandra. Here we focus on (1) the average X-ray properties of an optically selected, luminous sample of nine z>4 Palomar Digital Sky Survey quasars recently observed by Chandra, and (2) the X-ray spectral properties of three z>4 AGNs in the Chandra Deep Field-North (CDF-N) using the 2 Ms exposure. 
C. Vignali (1), W.N. Brandt (1), D.P. Schneider (1), G.P. Garmire (1),   S. Kaspi (2), F.E. Bauer (1), D.M. Alexander (1) ((...