Probing the Large Faraday Rotation Measure Environment of Compact Active Galactic Nuclei

Abstract

Knowing how the ambient medium in the vicinity of active galactic nuclei (AGNs) is shaped is crucial to understanding generally the evolution of such cosmic giants as well as AGN jet formation and launching. Thanks to the new broadband capability now available at the Jansky Very Large Array (JVLA), we can study changes in polarization properties, fractional polarization, and polarization angles, together with the total intensity spectra of a sample of 14 AGNs, within a frequency range from 1 to 12 GHz. Depolarization modeling has been performed by means of so-called “qu-fitting” to the polarized data, and a synchrotron self absorption model has been used for fitting to the total intensity data. We found complex behavior both in the polarization spectra and in the total intensity spectra, and several Faraday components with a large rotation measure (RM) and several synchrotron components were needed to represent these spectra. Here, results for three targets are shown. This new method of analyzing broadband polarization data through qu-fitting successfully maps the complex surroundings of unresolved objects.

Keywords

• polarization
• spectro-polarimetric study
• qu-fitting
• AGN surroundings