Triggers:AGN

Active Galactic Nuclei (AGNs)

AGNs: They are cosmologically distant sources, that can be used for fixing reference frames for studying motions of stars in the Galaxy and in the nearby galaxies within the Local Group. The energy radiated from the central engine is produced by accretion of matter onto the black hole. The emission from AGNs is observed at all wavelengths.

Optical appearance: In the optical part of the spectrum, AGNs are characterized by their long-term aperiodic variability with an amplitude of 0.5 magnitude in I-band. Majority of AGNs up to a redshift of z<2.6 occupy colors of 0.4<(V-I)<1.0 mag.

Spatial distribution: There are approximately 0.4, 4 and 40 AGNs per square degree brighter than I<16, 18 and 20 mag, respectively.