Some Properties an Active Galaxy May Possess
- High luminosity
- Nonthermal emission; possible excessive emission in X-ray, ultraviolet, infrared, and/or radio spectral regions in comparison to normal galaxies
- Variable emission; rapid variability in time, suggesting a small size for emitting region, but possibly some slow variability
- Compact appearance: peculiar appearance with high contrast in brightness between nucleus and rest of galaxy
- Explosive features: jetlike extensions out of galaxy's center or sometimes broad emission lines in spectrum of nucleus, indicating an outflow of matter, and in general nonstellar spectra
- Gravitational disturbance; large internal velocities and/or disturbed visual appearance at one or several points across the galaxy
- Large redshifts; average redshifts of active galaxies in following range for particular groups:
Seyfert galaxies, 0.0 < z < 0.2
N galaxies, 0.0 < z < 0.3
BL Lacertae objects, 0.1 < z < 0.5
radio galaxies, 0.0 < z < 0.8
quasars, 0.1 < z < 3.5
