exoALMA. II. Data Calibration and Imaging Pipeline

The exoALMA Large Program was designed to search for subtle kinematic deviations from Keplerian motion, indicative of embedded planets, in high-angular-resolution and high-spectral-resolution Band 7 observations of ¹²CO, ¹³CO, and CS emission from protoplanetary disks. This Letter summarizes the calibration and imaging pipelines used by the exoALMA collaboration. With sources ranging in diameter from 2.″4 to 13.″8 when probed by ¹²CO, multiple antennae configurations were required to maximally recover all spatial information (including Atacama Compact Array data for seven sources). Combining these data sets warranted particular care in their alignment during calibration and prior to imaging so as not to introduce spurious features that might resemble the kinematic deviations being investigated. Phase decoherence was found in several data sets, which was corrected by an iterative self-calibration procedure, and we explored the effects of the order of operations of spatial alignment, flux scaling, and self-calibration. A number of different imaging sets were produced for the continuum and line emission, employing an iterative masking procedure that minimizes bias due to non-Keplerian motions in the disk.