A Polarization Study of 3 Blazars using the uGMRT at ~600 MHz

TL;DR

This study uses the upgraded uGMRT at ~600 MHz to analyze the polarization properties of three blazars, revealing differences between blazar subclasses and jet structures, and demonstrating the feasibility of Band 4 polarization observations.

Contribution

First polarization study of blazars at ~600 MHz with uGMRT, comparing polarization properties across subclasses and revealing jet bending and depolarization effects.

Findings

Detected linear polarization in all sources.

Higher core polarization in quasars than in BL Lac object.

Observed jet bending and Laing-Garrington effect.

Abstract

We present results from our radio polarimetric study with the upgraded Giant Metrewave Radio Telescope (uGMRT) at Band 4 (550-850 MHz) of 3 blazars: radio-loud quasars 3C390.3, 4C71.07 and BL Lac object 1ES 2344+514. The aim of this study was (i) to carry out a feasibility study for Band 4 polarization with the uGMRT, and (ii) to compare and contrast the kpc-scale polarization properties between the blazar sub-classes. We have detected linear polarization in all the three sources. The degree of linear polarization in the cores of the two quasars is higher than in the BL Lac object, consistent with similar differences observed on parsec-scales in blazars. The highest fractional polarization of 15% is observed in the hotspot region of 3C390.3, which also shows extended polarized lobe structures. 1ES 2344+514 shows a core-halo structure whereas 4C71.07 remains unresolved. A rotation of polarization electric vectors along the northern hotspot of 3C390.3, and the core of 1ES 2344+514, suggest jet bending. Greater depolarization in the southern lobe of 3C390.3 compared to the northern lobe indicates the presence of the `Laing-Garrington effect'. Multi-frequency uGMRT polarimetric data are underway to study the kpc-scale rotation measures across these sources in order to look for differences in the surrounding media.