Molecules with ALMA at Planet-forming Scales (MAPS XVIII): Kinematic\n Substructures in the Disks of HD 163296 and MWC 480

Abstract

We explore the dynamical structure of the protoplanetary disks surrounding HD\n163296 and MWC 480 as part of the Molecules with ALMA at Planet Forming Scales\n(MAPS) large program. Using the $J = 2-1$ transitions of $^{12}$CO, $^{13}$CO\nand C$^{18}$O imaged at spatial resolutions of $\\sim 0.^{\\prime \\prime}15$ and\nwith a channel spacing of $200$ ${\\rm m\\,s^{-1}}$, we find perturbations from\nKeplerian rotation in the projected velocity fields of both disks\n($\\lesssim\\!5\\%$ of the local Keplerian velocity), suggestive of large-scale\n(10s of au in size), coherent flows. By accounting for the azimuthal dependence\non the projection of the velocity field, the velocity fields were decomposed\ninto azimuthally averaged orthogonal components, $v_{\\phi}$, $v_r$ and $v_z$.\nUsing the optically thick $^{12}$CO emission as a probe of the gas temperature,\nlocal variations of $\\approx\\! 3$ K ($\\approx\\! 5 \\%$ relative changes) were\nobserved and found to be associated with the kinematic substructures. The MWC\n480 disk hosts a suite of tightly wound spiral arms. The spirals arms, in\nconjunction with the highly localized perturbations in the gas velocity\nstructure (kinematic planetary signatures), indicate a giant planet, $\\sim\\! 1$\n$M_{\\rm Jup}$, at a radius of $\\approx 245$ au. In the disk of HD 163296, the\nkinematic substructures were consistent with previous studies of Pinte et al.\n(2018a) and Teague et al. (2018a) advocating for multiple $\\sim\\! 1$ $M_{\\rm\nJup}$ planets embedded in the disk. These results demonstrate that molecular\nline observations that characterize the dynamical structure of disks can be\nused to search for the signatures of embedded planets. This paper is part of\nthe MAPS special issue of the Astrophysical Journal Supplement.\n