Spectropolarimetry of 3CR 68.1: A Highly Inclined Quasar

Abstract

We present Keck spectropolarimetry of the highly polarized radio-loud quasar 3CR 68.1 (z = 1.228, V = 19). The polarization increases from 5% in the red (4000 Å rest frame) to greater than 10% in the blue (1900 Å rest frame). The broad emission lines are polarized the same as the continuum, which shows that 3CR 68.1 is not a blazar, as it has sometimes been regarded in the past. We also present measurements of the emission lines and a strong, blueshifted, associated absorption line system as well as a detection at the emission-line redshift of Ca II K absorption, presumably from stars in the host galaxy. Neither a blazar nor a partially obscured radio-quiet QSO, 3CR 68.1 belongs to an observationally rare class of highly polarized quasars. Taking into account the other unusual properties of 3CR 68.1, such as its extremely red spectral energy distribution and its extreme lobe dominance, we explain our spectropolarimetric results in terms of unified models. We argue that we have a dusty, highly inclined view of 3CR 68.1, with reddened scattered (polarized) quasar light diluted by even more dust-reddened quasar light reaching us directly from the nucleus.