The dependence of Polarization Degree of Blazars on particle energy distributions

TL;DR

This paper develops a formalism to predict the polarization degree of synchrotron emission from particles with specific energy distributions, applied to blazar Mrk 501, revealing how different distributions affect polarization observations.

Contribution

It introduces a new formalism for predicting polarization degree based on particle energy distributions and magnetic field configurations, applied to real blazar data.

Findings

Broken power law distribution cannot explain observed polarization unless higher energy particles have more ordered magnetic fields.

Log parabola distribution accounts for higher X-ray polarization compared to optical with uniform magnetic fields.

Future observations could distinguish between different particle energy distribution scenarios.

Abstract

We present a formalism to predict the Polarization Degree (PD) for synchrotron emission from particles having a specified energy distribution in the presence of an ordered and random magnetic field configuration. The broad band spectral energy distribution as well as the X-ray and optical PD data for Mrk 501 have been fitted using the formalism. As reported earlier, we find that for a broken power law particle energy distribution, the PD cannot be explained, unless it is assumed that the higher energy particles experience a higher ordered magnetic field compared to the lower energy ones. On the other hand, a log parabola particle energy distribution can explain the observed higher X-ray PD compared to the optical, even when all the particles experience the same magnetic configuration. We discuss the possibility of distinguishing the two scenarios using future observations.