The Optical Properties of PKS 1222+216 During the Fermi Mission

TL;DR

This study examines the optical properties of the quasar PKS 1222+216 during the Fermi mission, revealing a complex emission system with little correlation between optical and gamma-ray activity, and suggesting the jet's limited influence on broad emission lines.

Contribution

It provides detailed spectropolarimetric and spectrophotometric analysis of PKS 1222+216, highlighting the composite nature of its optical emission and the disconnect between optical and gamma-ray variability.

Findings

Optical emission comprises polarized synchrotron and unpolarized continuum.

Broad emission lines show little variability despite continuum changes.

Jet activity appears to have minimal impact on the broad emission-line region.

Abstract

The optical properties of the z = 0.435 quasar PKS 1222+216 (4C+21.35) are summarized since the discovery of impressive gamma-ray activity in this source by Fermi/LAT. Unlike several other gamma-ray-bright blazars, there appears to be little connection between optical and gamma-ray activity. Spectropolarimetry shows this object to be a composite system with optical emission from both a polarized, variable synchrotron power-law and unpolarized light from a stable blue continuum source (+broad emission-line region) contributing to the observed spectrum. Spectrophotometry over a period of about two years does not detect significant variability in the strong, broad emission lines, despite large optical continuum variations. This suggests that the relativistic jet has little influence on the output of the broad emission-line region, possibly either because the highly beamed continuum ionizes only a small portion of the line-emitting gas, or the observed non-thermal continuum originates parsecs downstream from the base of the jet, further away from the central engine than the broad emission-line region.