Spectropolarimetry of the luminous narrow-line Seyfert galaxies IRAS 20181-2244 and IRAS 13224-3809

We observed the narrow-line Seyfert 1 galaxies IRAS 20181-2244 and IRAS 13224-3809 with a new spectropolarimeter on the Ritchey-Chretien spectrograph at the CTIO 4 m telescope. Previously it had been suggested that IRAS 20181-2244 was a type 2 QSO and thus might contain an obscured broad-line region that could be detected by the presence of broad Balmer lines in the polarized flux. We found the object to be polarized at about 2% and constant with wavelength (unlike most narrow-line Seyfert 1 galaxies), but with no evidence of broad Balmer lines in polarized flux. The spectropolarimetry indicates that the scattering material is inside the broad-line region. IRAS 13224-3809, notable for its high variability in X-ray and UV wavelengths, has a low polarization consistent with a Galactic interstellar origin.