Hubble Space Telescope Imaging Polarimetry of the Inner Nuclear Region of NGC 1068

Abstract

We present the results of further Hubble Space Telescope (HST) imaging polarimetry of the inner region of NGC 1068 taken with the COSTAR corrected Faint Object Camera (FOC) in the ultraviolet (2400--2700 A). The centro-symmetric polarization pattern revealed by previous HST imaging polarimetry is shown to extend even closer to the illumination source (the hidden nucleus). Even in the inner region the ultraviolet light is dominated by scattered radiation, as the average polarization is approximately 20%, and it can be as high as 65%, figures which are similar to those obtained previously at larger radii. These new data allow a more accurate determination of the position of the source of scattered radiation that is displaced by 0."20 north and 0."06 west from the position recently obtained by Capetti et al. This new location of the nucleus rules out both cloud B and the "twin-crescent" as the nucleus of NGC 1068. In agreement with the unified model for Seyfert galaxies, there appears to be no visible counterpart at this location. The good agreement with previous polarimetric observations demonstrates the integrity of the polarization capabilities of the FOC obtained after the installation of COSTAR.