Polarimetric imaging with the GMRT

TL;DR

This paper demonstrates the first polarimetric imaging with the GMRT, showing calibration techniques to achieve high accuracy and presenting polarization images of two radio galaxies at 610 MHz.

Contribution

It introduces the first polarimetric imaging with GMRT and details calibration methods for spectral leakage correction.

Findings

Instrumental polarization leakage varies with frequency.

Calibration can achieve better than 1% accuracy.

Polarization fractions are consistent with previous surveys.

Abstract

We present the first set of polarimetric images made with the GMRT. These were obtained as part of the program to commission the polarization mode at the telescope. We find that the instrumental polarization leakage at the GMRT varies with frequency. It is hence necessary to solve for the leakage as a function of spectral channel. Once this is done however, it is possible to calibrate these terms to better than 1% accuracy, making it feasible to study sources that are polarized at the few percent level. We present 610 MHz polarization images of two extended FR-II radio galaxies, viz. 3C 79 and 3C 265. These were selected from the sample of sources for which the total polarization fraction at 610 MHz is known from the survey of Conway & Strom (1984). We present high resolution polarization images of these two sources and also find that the polarization fractions of the two sources as seen at the GMRT are consistent with those reported by Conway & Strom (1984).