Revealing the Effects of Orientation in Composite Quasar Spectra
Abstract
We present low-resolution, composite optical spectra for 60 quasars drawn from the 408 MHz--selected Molonglo Quasar Sample. Individual spectra have been co-added according to the ratio of radio core-to-lobe flux density R in order to show global changes as a function of quasar orientation. Compact steep-spectrum (CSS) quasars have been combined separately. With increasing implied viewing angle to the radio-jet axis, we find that (1) the optical continuum steepens, (2) the 3000 A broad emission feature decreases in relative strength, and (3) the narrow-line equivalent widths, broad-line widths, and Balmer decrements increase. The composites show that reddening is considerable in most lobe-dominated quasars (AV ~ 2--4). Moreover, the extinction appears to be aspect-dependent, which suggests an intrinsic origin for the dust. The CSS composite spectrum is particularly striking, showing evidence for significant reddening, a steep power-law continuum, relatively strong low-ionization narrow-line emission, and no discernible 3000 A bump.
- Publication:
-
The Astrophysical Journal
- Pub Date:
- October 1995
- DOI:
- 10.1086/309726
- Bibcode:
- 1995ApJ...452L..95B
- Keywords:
-
- GALAXIES: ACTIVE;
- GALAXIES: QUASARS: GENERAL;
- GALAXIES: QUASARS: EMISSION LINES