A polarization study of three blazars using uGMRT at ∼600 MHz

Abstract

We present results from our radio polarimetric study with the upgraded giant metrewave radio telescope (uGMRT) at band 4 (550–850 MHz) of three 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 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 Laing–Garrington effect. Multi-frequency uGMRT polarimetric data are underway to study the kpc-scale rotation measures across these sources to find differences in the surrounding media.