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A High-Resolution View of Planet Formation Signatures in exoALMA Protoplanetary Disks

Presentation #621.01 in the session Protoplanetary Disks - Observations.

Published onApr 03, 2024
A High-Resolution View of Planet Formation Signatures in exoALMA Protoplanetary Disks

In recent years, protoplanetary disks have been observed at high enough resolutions to detect and characterize a variety of disk substructures, some of which are indicative of active planet formation. The planet-hunting ALMA large program exoALMA has observed 15 protoplanetary disks at high angular and spectral resolution, characterizing disk structures and kinematics in enough detail to detect non-Keplerian features (NKFs) caused by forming protoplanets. As these signatures of young planets can be faint and tiny, robust imaging procedures are critical for detecting embedded protoplanets at high confidence. The exoALMA collaboration is employing two different imaging procedures to ensure that we consistently detect the NKFs: CLEAN, the traditional iterative deconvolution process, and Regularized Maximum Likelihood (RML), an imaging process recently popularized by the Event Horizon Telescope Collaboration. RML produces an image by maximizing the likelihood of visibility data given predicted model visibility values and regularizers. Applying RML imaging techniques to sub-mm interferometric observations can achieve higher angular resolution and image fidelity compared to CLEAN, and serve as an independent verification of marginal features seen in CLEAN images. We used the open source Python package MPoL to obtain RML images from the exoALMA observations of several protoplanetary disks with tentative NKFs. We find that RML imaging methods successfully reproduce the NKFs seen in the CLEAN images of the 12CO emission around LkCa 15, SY Cha, and RXJ1842.9-3532, suggesting that the NKFs are real features rather than artifacts from a specific imaging procedure. We also present a comparison of CLEAN and RML image analyses, including retrievals of emission heights, surface temperatures, and gas velocities.

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