The Optical Polarization and Warm Absorber in IRAS [FORMULA][F]17020+4544[/F][/FORMULA

Abstract

We report the detection of ionized absorption in the ASCA spectrum of the narrow-line Seyfert 1 galaxy IRAS 17020+4544. Subsequent optical spectropolarimetry revealed high polarization increasing from 3% in the red to 5% in the blue, which indicates electron or dust scattering as a likely origin. The broad emission line Hα is somewhat less polarized than the continuum, which supports a location of the polarizing material within the active galactic nucleus. The Balmer line decrement and reddened optical spectrum support the presence of a dusty warm absorber in this object. We compared the broadband optical polarization and ionized X-ray absorption of a collection of Seyfert 1 and 1.5 galaxies, excluding classes of objects that are likely to have significant neutral X-ray absorption. Warm absorber objects are generally more likely to have high optical polarization than objects with no detected ionized absorption. This result lends additional support to the idea that the warm absorber is associated with dust and implies either that dust transmission is responsible for at least part of the polarization or that the polarization is revealed because of the dimming of the optical spectrum. Spectropolarimetry of Seyfert 1 galaxies generally locates the scattering material inside the narrow-line region and often close to or within the broad-line region, consistent with estimates of the location of the dusty warm absorber.