Intermediate Resolution Spectropolarimetry of Three Quasars

Summary

Abstract

We present spectropolarimetric observations of the quasars 3C273, CTA102 and 3C345. A synchrotron origin is the most likely explanation for the polarization of 3C273. The quasar CTA102 may have strongly polarized FeII lines and, along with 3C345, some minima in the polarization are alongside the red wing of the MgII and CIII] lines.

Introduction

An often debated problem is that of the variability and polarization of the emission lines in AGNs. Despite the work done on Seyfert-2 and radio galaxies (e.g., McLean et al. 1983; Antonucci & Miller 1985; Antonucci 1992; Jackson in this meeting) and on quasars (Goodrich & Miller 1988), which demonstrates that the lines are usually polarized, the lack of appropriate instruments has severely limited the number of research groups dedicated to this important task.

The aims of our observations were, first, to get a spectropolarimetric sample of quasars. The objects are chosen for a) their brightness, brighter than 17 mag, b) their polarization, larger than 3%, and c) their known variability. Besides these, some other objects, like 3C273, of which polarization has never been reported to be larger than 2.5%, were also included in the sample. The second aim is to see if the emission lines are polarized and search for possible variability. Comparing lines and their continuum polarization and variability we should find new and powerful parameters for studying the actual models for quasars and for the origin of their polarized radiation.