Speaker
Description
I will present a summary of observations of active galaxies from the Imaging X-ray Polarimetry Explorer (IXPE). For radio quiet AGN such as NGC 1068 and the Circinus Galaxy, X-ray polarization results from scattering from the corona above the disk or from the inner wall of a molecular torus. Blazars whose synchrotron spectra peak at high frequencies (in or near the X-ray band), denoted as HBLs, are generally found to be polarized at the 10-30% level. Examples include Mk 501 and Mk 421. They can have quite variable polarization both in degree and position angle -- likely related to the jet on parsec scales. Optical polarization is much lower than the X-ray polarization in these cases, supporting a model where electrons are accelerated in shocks travel downstream to regions of increasingly disordered field. By contrast, for blazars with low frequency synchrotron emission (LBLs), such as 3C 273, 3C 279, and 3C 454.3, have X-ray spectra dominated by Compton upscattered photons. X-ray polarization has not been detected in LBLs at levels of 10% or less. For these sources, we favor models where the X-ray band is dominated by unpolarized photons upscattered by relativistic electrons in relativistic jets. The parameter space for hadronic models is severely constrained. The IXPE observations have been critically supported by contemporaneous multiwavelength polarization campaigns, required for a holistic view of blazar emission.
