2025ApJ...984L...6T

Planet formation is a hugely dynamic process requiring the transport, concentration, and assimilation of gas and dust to form the first planetesimals and cores. With access to observations with extremely high spatial and spectral resolution at unprecedented sensitivities, it is now possible to probe the planet-forming environment in detail. To this end, the exoALMA Large Program targeted 15 large protoplanetary disks, ranging between ∼1″ and ∼7″ in radius, and mapped the gas and dust distributions. ¹²CO J = 3-2, ¹³CO J = 3-2, and CS J = 7-6 molecular emission was imaged at high angular ($\sim 0\mathop{.}\limits^{^{\prime\prime} }15$) and spectral (∼100 m s^–1) resolution, achieving a surface brightness temperature sensitivity of ∼1.5 K over a single channel, while the 330 GHz continuum emission was imaged at 90 mas resolution and achieved a point source sensitivity of ∼40 μJy beam^–1. These observations constitute some of the deepest observations of protoplanetary disks to date. Extensive substructure was found in all but one disk, traced by both dust continuum and molecular line emission. In addition, the molecular emission allowed for the velocity structure of the disks to be mapped with excellent precision (uncertainties of the order of 10 m s^–1), revealing a variety of kinematic perturbations across all sources. From this sample it is clear that, when observed in detail, all disks appear to exhibit physical and dynamical substructure indicative of ongoing dynamical processing due to young, embedded planets, large-scale (magneto)hydrodynamical instabilities or winds.