Deconvolved IXPE Polarization Maps of the Crab Nebula in a Maximum-a-Posteriori Framework

Abstract

We analyze the first IXPE observation of the Crab Nebula using a polarization-resolved deconvolution method based on maximum a posteriori (MAP) estimation. The method reconstructs the polarization-resolved intensity map as a three-dimensional distribution in sky-position and polarization-angle spaces, using an instrumental response that depends on the incident direction and polarization angle of X-ray photons. We apply the method to the IXPE data in the 2-8~keV band and compare the result with that obtained using the basic analysis. Our result shows sharper spatial structure, making the jet shape more clearly identifiable than that in the basic analysis. The reconstructed image shows a statistically significant tendency for the magnetic-field orientation to be perpendicular to the intensity-gradient orientation in the jet region. Although these results are obtained by using a simplified response where systematic uncertainty remains, they demonstrate that our MAP-based deconvolution can improve the interpretability of IXPE polarization maps for nebular sources.