exoALMA. XVIII. Interpreting large scale kinematic structures as moderate warping

TL;DR

This paper proposes that moderate warps in protoplanetary disks can explain large-scale kinematic features observed by exoALMA, linking disk warping to observable velocity structures and potential planet formation processes.

Contribution

It introduces a simple model interpreting velocity variations as disk warps, suggesting warps are common and influence disk morphology and dynamics.

Findings

Moderate warps can explain large-scale velocity features.

Warp-induced structures can produce spiral patterns in scattered light.

Warp properties correlate with stellar accretion rates.

Abstract

The exoALMA program gave an unprecedented view of the complex kinematics of protoplanetary disks, revealing diverse structures that remain poorly understood. We show that moderate disk warps ($\sim 0.5-2^\circ$) can naturally explain many of the observed large-scale velocity features with azimuthal wavenumber $m = 1$. Using a simple model, we interpret line-of-sight velocity variations as changes in the projected Keplerian rotation caused by warping of the disk. While not a unique explanation, this interpretation aligns with growing observational evidence that warps are common. We demonstrate that such warps can also produce spiral structures in scattered light and CO brightness temperature, with $\sim 10$ K variations in MWC 758. Within the exoALMA sample, warp properties correlate with stellar accretion rates, suggesting a link between the inner disc and outer disc kinematics. If warps cause large-scale kinematic structure, this has far reaching implications for turbulence, angular momentum transport, and planet formation.