Colloq Abstract - Sekhar
December 13, 2022
11:00am Mountain
Srikrishna Sekhar (IDIA)
High Fidelity Imaging at Radio Frequencies
Abstract
This talk will describe the work that I have been doing to enable accurate, high fidelity imaging at radio frequencies. This includes work on novel radio frequency interference (RFI) flagging algorithms, high performance calibration pipelines, and full Stokes primary beam modeling. I will also highlight some science that has been facilitated by these developments. I briefly describe these developments below.
RFI is an ubiquitous issue that affects a large number of radio observing bands. I have previously developed a flagging algorithm called GRIDflag that identifies and flags RFI in the UV-domain, preserving UV coverage while eliminating RFI. Preserving UV coverage has the twin advantages of retaining sensitivity to sky emission at different scales, and maintaining deconvolution accuracy.
In order to process the large data volumes routinely generated by today's telescopes (JVLA, MeerKAT, uGMRT etc.) it is imperative to have a calibration pipeline that can process the data on reasonable timescales. I discuss the CASA-based automated parallel, full Stokes IDIA calibration pipeline, which has been deployed on the ilifu cluster in Cape Town to calibrate MeerKAT data. We routinely achieve calibration times that are only a fraction of the total observing time (< 0.5T_obs), while producing near thermal noise limited fullStokes images.
Performing widefield polarimetry requires that the leakage patterns from the antenna primary beam are taken care of. I will describe the work we have
done to obtain accurate full Stokes PB models for JVLA, MeerKAT & ALMA. The modeling method can be used to generate PB models for any telescope with antenna holography. I also describe a standalone package to perform image plane leakage corrections using these models.
Finally, I will also discuss the corresponding astrophysics that has been made possible by these technical developments - namely, deep spectral index maps of
restarting AGN, and the first results from the MeerKAT MIGHTEE polarization survey.
