High Velocity Outflows in AGNs Observed with Gratings

Several Active Galactic Nuclei (AGNs) have been reported to harbor fast outflows exceeding 10,000 km?s^?1, which are detected mostly in their low-resolution CCD X-ray spectra. Only few, however, were detected with high-resolution grating spectrometers. Most of the grating detected outflows have been observed multiple times. In these cases, the absorption spectrum changes are indicating that variability is common among these high-velocity winds. In this paper we revisit the grating observations of PG?1211+143, and PDS?456, and report preliminary results on 4C?74.26. We discuss the spectral variability of the first two sources and its implications to the outflows.     

X-rays from the first massive black holes

X-ray studies of high-redshift (z > 4) active galaxies have advanced substantially over the past few years, largely due to results from the new generation of X-ray observatories. As of this writing X-ray emission has been detected from nearly 60 high-redshift active galaxies. This paper reviews the observational results and their implications for models of the first massive black holes, and it discusses future prospects for the field.