exoALMA. XVIII. Interpreting Large-scale Kinematic Structures as Moderate Warping
Andrew J. Winter, M. Benisty, Andrés F. Izquierdo, Giuseppe Lodato, Richard Teague, C. N. Kimmig, Smaranda Andrews, Jaehan Bae, Marcelo Barraza-Alfaro, Nicolás Cuello, Pietro Curone, Ian Czekala, Stefano Facchini, Daniele Fasano, Cassandra Hall, Caitlyn Hardiman, Thomas Hilder, John D. Ilee, Misato Fukagawa, Cristiano Longarini, F. Ménard, Ryuta Orihara, C. Pinte, Daniel J. Price, Giovanni Rosotti, Jochen Stadler, David J. Wilner, Lisa Wölfer, Hsi-Wei Yen, Tomohiro C. Yoshida, Brianna Zawadzki
Abstract
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 (∼0 <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mover> <mml:mrow> <mml:mo>.</mml:mo> </mml:mrow> <mml:mrow> <mml:mtext>°</mml:mtext> </mml:mrow> </mml:mover> </mml:math> 5–2°) 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 ∼10 K variations in MWC 758. Within the exoALMA sample, warp properties correlate with stellar accretion rates, suggesting a link between the inner disk and outer disk kinematics. If warps cause large-scale kinematic structure, this has far-reaching implications for turbulence, angular momentum transport, and planet formation.