The orientation dependence of quasar spectral energy distributions

TL;DR

This study examines how the orientation of radio-loud quasars affects their spectral energy distributions, revealing luminosity dependence on orientation but little change in overall spectral shape across wavelengths.

Contribution

It provides the first detailed analysis of orientation effects on quasar spectral energy distributions using a well-selected sample with radio core dominance measurements.

Findings

Luminosities are 2-3 times brighter in face-on quasars.

Spectral shape remains consistent regardless of orientation.

Infrared anisotropy does not decrease with wavelength.

Abstract

We investigate the orientation dependence of the spectral energy distributions in a sample of radio-loud quasars. Selected specifically to study orientation issues, the sample contains 52 sources with redshifts in the range 0.16<z<1.4 and measurements of radio core dominance, a radio orientation indicator. Measured properties include monochromatic luminosities at a range of wavelengths between the infrared and X-rays, integrated infrared luminosity, spectral slopes, and the covering fraction of the obscuring circumnuclear dust. We estimate dust covering fraction assuming that the accretion disk emits anisotropically and discuss the shortcomings and technical difficulties of this calculation. Luminosities are found to depend on orientation, with face-on sources factors of a 2-3 brighter than more edge-on sources, depending on wavelength. The degree of anisotropy varies very little with wavelength such that the overall shape of the spectral energy distribution does not vary significantly with orientation. In the infrared, we do not observe a decrease in anisotropy with increasing wavelength. The spectral slopes and estimates of covering fraction are not significantly orientation dependent. We construct composite spectral energy distributions as a function of radio core dominance and find that these illustrate the results determined from the measured properties.