Are Quasars Fractal ?

In this paper we show that bright emission lines of quasars and other active galactic nuclei (AGNs) are reproduced if the gas distribution in the central parsec of these objects has a fractal geometry. While the detailed nature of AGN clouds is unknown recent models invoke magnetohydrodynamic (MHD) effects to explain their persistence. Numerical simulations of MHD turbulence have shown that a fractal cloud distribution is a result. Whatever the mechanism, fractal structure is observed in nature and may be present in AGNs as well. We therefore test a fractal distribution of gas in the broad line region (BLR) by calculating various emission line ratios it produces when illuminated by an AGN continuum and then comparing these to line ratios obtained from observations. We find eight out of eleven emission line ratios are reproduced. Additional successes of the model are that it explains the persistence of broad line region clouds without invoking a special confinement mechanism, it explains the number and column density of line of sight absorbers, and predicts the observed frequency of nuclear activity in galaxies.