Polarimetric images with the GMRT

Probing Magnetic Fields using the Giant Metrewave Radio Telescope

“…The detected source has a polarisation fraction of 6.9±0.5%, although the source of the polarised emission along the line of sight cannot be investigated in detail given the limited resolution. Furthermore, the source located at 13h32m45.1s, 47 • 22 22.6 (#13 in Table 1) is coincident with the radio galaxy B3 1330+476 located at a redshift of z = 0.67 (Schneider et al 2005).…”

“…For the more rigorous approach of holographic observations of the GMRT beam, see Farnes, (2012). Note that Pen et al (2009) show that this radial orientation is anticipated as leakage across the beam is expected to vary in a quadrupolar pattern. This is due to the GMRT's prime-focus feeds being mounted on four support legs which each have a width comparable to the observing wavelength.…”

“…The peak in the P image created from band-averaged Q and U was used to place an upper limit on the polarisation fraction of unpolarised sources. This procedure tends to overestimate the polarisation fraction, as the bias correction does not work well for low signal-to-noise levels (Simmons & Stewart 1985). Nevertheless, the calculated values serve as an upper limit on the polarisation fraction.…”

“…The "full-polarisation" mode of the Giant Metrewave Radio Telescope (GMRT) has recently become available for such observations. Imaging of GMRT polarisation data has been previously attempted in the 610 MHz band using the bandwidth-averaged Stokes Q/U (Joshi & Chengalur 2010). Nevertheless, as with all new instrumental modes of operation, the facility requires efforts to understand the various intrinsic limitations to such observations, such as the instrumental polarisation, instrumental time-stability, quality of uvdata calibration, ionospheric Faraday rotation, polarisation angle corrections across the observing bandwidth, and the wide-field response.…”

“…Anderson et al 2012), and the upgraded Jansky-VLA (JVLA) at 1.0 GHz (e.g. Perley et al 2009). The GMRT itself is currently undergoing an upgrade that will further improve upon its science capabilities (Gupta, 2011).…”