exoALMA XXII: A Two-dimensional Atlas of Deviations from Keplerian Disks

TL;DR

This study presents a comprehensive 2D atlas of gas kinematic deviations from Keplerian rotation in 15 protoplanetary disks, revealing widespread substructures such as spirals and rings that indicate complex physical processes and potential planet formation.

Contribution

First systematic 2D mapping of gas deviations in a large, uniform sample of protoplanetary disks, highlighting the ubiquity and variety of kinematic substructures.

Findings

All disks show deviations from Keplerian rotation.

Spiral-like features are detected in several Herbig Ae/Fe disks.

Kinematic substructures are common in large, young disks.

Abstract

Protoplanetary disks are the birthplaces of planetary systems, and deviations from Keplerian rotation imprinted in disk gas kinematics serve as key tracers of physical processes and the presence of protoplanets within disks. Using the the CO (J=3-2) data from the exoALMA Large Program encompassing 15 disks, we constructed two-dimensional (2D) maps of centroid velocity, line width, and peak intensity, and extracted non-Keplerian deviations by subtracting smooth Keplerian models. This paper provides the first systematic and uniform overview of 2D gas substructures across the entire exoALMA sample. We find that all targets exhibit large-scale deviations from smooth Keplerian disks, displaying a variety of morphologies including spiral-like structures, arc- or ring-like features, and patterns indicative of variations in the emitting surface height. Non-axisymmetric spiral-arm features are detected or suggested in five disks (CQ Tau, MWC 758, HD 135344B, HD 34282, and SY Cha), and are preferentially found in Herbig Ae/Fe systems. In contrast, some other sources (J1852, PDS 66, and V4046 Sgr), despite exhibiting noticeable deviations, appear to be dynamically quieter. This 2D atlas suggests that kinematic substructures are ubiquitous in large ($\gtrsim$ 100 au) protoplanetary disks with ages of a few million years, based on the observations obtained with sufficient sensitivity at moderate-to-high spatial resolution of $\sim$20 au and high velocity resolution of $\sim$0.1 km s$^{-1}$.