Reverberation Mapping of Broad Line Regions in Actvie Galactic Nuclei

The time-delay between the emission-line variations and the continuum variations of a quasar or Seyfert galaxy can be used to estimate the distance between the broad line regions (BLRs) and the central source, and this technique is called the emission-line reverberation mapping (RM). Based on the RM observation, a relationship between the size of BLRs (RBLR) and the luminosity of AGNs can be established. With this relation, the mass of the central black hole in the quasar SDSS J1148+5251 is estimated to be 3×10 M⊙. Based on the RM measurements of some high-luminosity and low-luminosity objects in recent years, a RBLR-luminosity relation over 7 orders of magnitude in luminosity can be determined. Some further prospects of RM technique include the 2-D RM, infrared RM of dust torus, and the RM in X-ray band.