Conference Report

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

“…These data were obtained after the COSTAR deployment, but at the time of this polarimetry observation HST had an extraordinarily poor focus due to a large movement of the secondary mirror, the effect of which will be discussed in detail below. Therefore, the images through different polarizers (POL0, POL60, POL120), which are known to be slightly shifted relative to one another, were registered by using the image shift values of calibrations by Hodge (1993Hodge ( , 1995, not by using point-like sources in the outer region. Then the images were scaled according to the exposure times and the transmittances of the polarizers and the F253M filter.…”

“…(2) Uncertainty from the image registrations of three polarizer images. As described in § 2.1, we have registered the images using the calibrated values of Hodge (1995) and their wavelength dependence by Hodge (1993). The calibrated image shifts have an uncertainty of about ±0.3 pixel.…”

“…(ii) Differences in PSFs through each polarizer result in uncertainties in these multiplying factors locally. We estimate this effect from the result given by Hodge (1995), who has investigated the differences in the fluxes of unpolarized point sources through different polarizers over various aperture sizes. Although this is for data with nominal focus, the maximum uncertainties for our out-of-focus data can be estimated for each of our binning size (A), (B) and (C) above, from the flux differences of smaller aperture size in Hodge's result.…”

“…The statistical error in the photon counts σ stat P is a random error, while the other three errors, each described below, would be systematic errors. We treat P , is estimated by actually shifting the images with the calibration uncertainties of 0.3 pixel (Hodge 1995) and calculating the resulting change of P . The other errors are calculated using equations (A2) ∼ (A8) in the following way.…”