Software

GPCAL

I wrote GPCAL, a novel instrumental polarization calibration pipeline for VLBI data. It overcomes several limitations in existing calibration tools and improves calibration accuracy and dynamic ranges of linear polarimetric images. GPCAL has already been applied to the polarization analysis of the first M87 EHT results (EHTC2021+). Furthermore, it has revealed a linear polarimetric structure in the subparsec core of the M87 jet at 43 GHz, which has not been possible with existing calibration tools due to the limited accuracy. The new linear polarization image of M87 based on Very Long Baseline Array (VLBA) observations at 43 GHz is shown below. More details can be found here. The code is available on GitHub.

*Image of the M87 jet observed with the VLBA at 43 GHz. The colored ticks show linear polarization vectors.