Structure of the Seyfert broad line region and absorption region of NGC 4151

摘要

The Seyfert nucleus of NGC 4151 was monitored for six years, including periods of intensive study of the complex variations in the ultraviolet spectra with IUE. Important IUE results relating to the broad line region (BLR) and its physical conditions are reviewed herein. Active galactic nuclei like NGC 4151 are studied to derive detailed constraints on radiation mechanisms and physical conditions in the emission region, and hence also constraints on possible central power sources. The ultraviolet spectrum of NGC 4151 comprises continuum, strong emission lines with different widths along with a rich absorption line spectrum. Variations in the broad absorption lines seem to derive principally from changes in column densities of absorbing species rather than in velocity dispersions or line profiles.