The luminosity dependence of the Type 1 AGN fraction

Using a complete, magnitude-limited sample of active galaxies from the Sloan Digital Sky Survey (SDSS) we show that the fraction of broad-line (Type 1) active galactic nuclei increases with luminosity of the isotropically-emitted [O III] narrow emission line. Our results are quantitatively in agreement with, and far less uncertain than, similar trends found from studies of X-ray and radio-selected active galaxies. While the correlation between broad-line fraction and luminosity is qualitatively consistent with the receding torus model, its slope is shallower and we therefore propose a modification to this model where the height of the torus increases slowly with AGN luminosity. We demonstrate that the faint-end slope of the AGN luminosity function steepens significantly when a correction for `missing' Type 2 objects is made and that this can substantially affect the overall AGN luminosity density extrapolated from samples of more luminous objects.Comment: 8 pages, accepted for publication by MNRA

Quasars are more luminous than radio galaxies - so what?

Surveys to find high-redshift radio galaxies deliberately exclude optically-bright objects, which may be distant radio-loud quasars. In order to properly determine the space density of supermassive black holes, the fraction of such objects missed must be determined within a quantitative framework for AGN unification. I briefly describe the receding torus model, which predicts that quasars should have more luminous ionizing continua than radio galaxies of similar radio luminosity, and present evidence to support it. I also suggest two further tests of the model which should constrain some of its parameters.Comment: 6 pages. To appear in "Radio galaxies: past, present and future", eds M. Jarvis et al., Leiden, Nov 200

Near-infrared and X-ray obscuration to the nucleus of the Seyfert 2 galaxy NGC 3281

We present the results of a near-infrared and X-ray study of the Seyfert 2 galaxy NGC 3281. Emission from the Seyfert nucleus is detected in both regions of the electromagnetic spectrum, allowing us to infer both the equivalent line of sight hydrogen column density, N_H = 71.0(+11.3,-12.3)e26/m^2 and the extinction due to dust, A_V = 22+/-11 magnitudes (90% confidence intervals). We infer a ratio of N_H/A_V which is an order of magnitude larger than that determined along lines of sight in the Milky Way and discuss possible interpretations. We consider the most plausible explanation to be a dense cloud in the foreground of both the X-ray and infrared emitting regions which obscures the entire X-ray source but only a fraction of the much larger infrared source.Comment: 23 pages including 9 figure

The detection and photometric redshift determination of distant galaxies using SIRTF's Infrared Array Camera

We investigate the ability of the Space Infrared Telescope Facility's Infrared Array Camera to detect distant (z ~ 3)galaxies and measure their photometric redshifts. Our analysis shows that changing the original long wavelength filter specifications provides significant improvements in performance in this and other areas.Comment: 28 pages incl 12 figures; to appear in June 1999 PASP. Fig.12 replaced with corrected versio