Spectral evolution in young active galactic nucleiThe spectral evolution of AGNs is discussed within the context of a scenario where the cosmic X-ray background (CXB) is dominated by these sources. Attention is draqwn to the fact that the individually observed AGN X-ray spectra are significantly steeper than that of the CXB. The remarkably flat spectrum thereby required for the 'as-yet' unresolved sources of the residual CXB is interpreted as an observational constraint on an earlier stage of AGN evolution. Assuming black hole disk accretion, a picture emerges where young AGNs are compact Eddington limited thermal X-ray sources and where canonical AGNs represent later stages in which they have become appreciably less compact, exhibiting the importance of nonthermal disk-dynamo processes.
Document ID
19870025999
Acquisition Source
Legacy CDMS
Document Type
Conference Paper
Authors
Boldt, E. (NASA Goddard Space Flight Center Greenbelt, MD, United States)
Leiter, D. (NASA Goddard Space Flight Center Greenbelt, MD, United States)