The Location of the Nucleus of NGC 1068 and the Three‐dimensional Structure of Its Nuclear Region

The HST archival UV imaging polarimetry data of NGC 1068 is re-examined.Through an extensive estimation of the observational errors, we discuss whetherthe distribution of the position angles (PAs) of polarization is simplycentrosymmetric or not. Taking into account the effect of a bad focus at thetime of the observation, we conclude that, within the accuracy of HST/FOCpolarimetry, the PA distribution is completely centrosymmetric. This means thatthe UV polarization originates only from scattering of the radiation from acentral point-like source. However, our analysis shows that the most probable location of the nucleus isonly ~0.''08 (~6pc) south from the brightest cloud called ``cloud B''. Theerror circle of 99% confidence level extends to cloud B and to ``cloud A''which is about 0.''2 south of cloud B. By this FOC observation, Cloud B is onlymarginally rejected as the nucleus. Assuming that the UV flux is dominated by electron-scattered light, we havealso derived a three-dimensional structure of the nuclear region. The inferreddistribution suggests a linear structure which could be related to the radiojet.Comment: 19 pages, 14 figures, to be published in the Astrophysical Journa