| Abstract : | Active galactic nuclei (AGN) are luminous sources powered by accretion of matter onto super massive black holes (SMBHs). It is difficult to resolve their central regions (SMBH, accretion disk, broad line region (BLR) and dusty torus) by direct imaging techniques. However, using the flux variability characteristics of AGN, one can probe their central regions indirectly using reverberation mapping (RM). The technique of RM is based on the light travel time delayed response of the line emitting gas as well as the re-processed torus emission to changes in the continuum emission from the accretion disk. In this thesis, we used RM observations to characterise the central regions of AGN. From photometric observations of Mrk 590 using both broad and narrow band filters, we found the BLR size to be 21.44(+1.49/-2.11) days which is equivalent to 0.018(+0.001/−0.002) pc. Combining these photometric observations with the newly acquired Subaru spectrum we found a black hole mass of 1.96(+0.15/−0.21 ×10^8)Msun. Similarly, from long term monitoring in the optical and near infrared bands, we found the inner edge of the dust torus in H0507+164 and Z229−15 to be 0.029(+0.010/−0.008) pc and 0.017(+0.005/−0.005) pc, respectively. From an analysis of the RM data collected from literature, for a total of 57 AGN, using Bayesian approach, we constrained the size, structure and kinematics of the BLR in them. As, RM relies on the variability property of AGN, AGN are ideal targets for RM studies. Therefore, this thesis arrived at a catalogue of 6738 quasars that will the covered by the upcoming international Liquid Mirror Telescope of the ARIES, Nainital. As the same region of the sky will be repeatedly seen by ILMT, variable quasars can easily be identified from this catalogue. These quasars, in addition to being excellent targets for RM studies, can also serve as astrometric calibrators for ILMT. |
