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The ALMA survey to Resolve exoKuiper belt Substructures (ARKS) I: Motivation, sample, data reduction, and results overview

The outer regions of planetary systems host dusty debris discs analogous to the Kuiper belt (exoKuiper belts), which provide crucial constraints on planet formation and evolution processes. ALMA dust observations have revealed a great diversity, and that some belts contain CO gas, whose origin and implications are uncertain. Most of this progress, however, has been limited by low-resolution observations. We conducted the first ALMA large programme dedicated to debris discs: the ALMA survey to Resolve exoKuiper belt Substructures (ARKS). We selected the 24 most promising belts to constrain their detailed radial and vertical structure, and to characterise the gas content. We constrained the radial and vertical distribution of dust, as well as the presence of asymmetries. For a subset of six belts with CO gas, we constrained the gas distribution and kinematics. To interpret these observations, we used a wide range of dynamical models. The first ARKS results are presented as a series of ten papers. We discovered that up to 33% of our sample exhibits multiple dusty rings. For highly inclined belts, we found that non-Gaussian vertical distributions are common and are indicative of multiple dynamical populations. We also found that 10 of the 24 belts present asymmetries. We find that the CO gas is radially broader than the dust, but this could be an effect of optical depth. At least one system shows non-Keplerian kinematics due to strong pressure gradients, which may have triggered a vortex that trapped dust in an arc. Finally, we find evidence that the micron-sized grains may be affected by gas drag in gas rich systems. ARKS has revealed a great diversity of structures in exoKuiper belts that may arise when they are formed in protoplanetary discs or subsequently via interactions with planets and/or gas. We encourage the community to explore the reduced data and data products.