Affiliated to the Astrophysics Division, Space Science Department, European Space Agency
On leave from Dipartimento di Fisica, II Università di Roma, Italy
ABSTRACT. Active Galactic Nuclei (AGN) are now known to be strong
-ray
emitters. After briefly describing AGN classification and the main ideas
behind unified schemes, I summarize the main properties of blazars (that
is BL
Lacs and flat-spectrum radio quasars) and their connection with relativistic
beaming. Finally, I address the question of why blazars, despite being
extreme and very rare objects, are the only AGN detected at high
(E > 100 MeV) energies, and touch upon the relevance of TeV
astronomy for AGN research.
Table of Contents
ACTIVE GALACTIC NUCLEI
The
AGN Zoo
Unified
Schemes
BLAZARS
AS -RAY SOURCES
Blazar Properties and Relativistic Beaming
THE
IMPORTANCE OF BEING A BLAZAR
AGN AS
TeV SOURCES
SUMMARY
REFERENCES
