Broad Line Region

This model of the broad line region (BLR) is based on the echo-mapping of nearby low-luminosity quasars. Echo-mapping is a technique where all of the light from a quasar is monitored over several weeks or months. The light from the BLR clouds (the emission lines) changes in response to light from the centre (probably the accretion disc) - effectively a light echo. The time it takes to change and the way it changes indicates the distance and shape of the clouds' regions. The animation is taking you around the outer low-ionization regions then zooming into the inner, high-ionization zone.

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This page written by Liz Puchnarewicz (
Last modified 17th March 1998