Understanding the origin of substructures in protoplanetary discs is central to constraining planet formation, yet most high-resolution studies remain biased toward a small number of bright, massive discs. In this talk, I will present results from a comprehensive high-resolution analysis of approximately 100 discs from the Ophiuchus Disk Survey Employing ALMA (ODISEA), spanning a wide range of continuum fluxes from ∼4 to 400 mJy at 225 GHz.
Using ALMA Band 8 continuum observations at 0.7 mm, we probe disc substructures across nearly two orders of magnitude in disc mass, extending down to systems containing only a few Earth masses of dust. By fitting non-parametric models directly to the visibilities, we achieve sub-beam resolution and systematically classify disc morphologies into an evolutionary sequence ranging from featureless discs to systems with gaps, rings, and central cavities. This allows us to investigate how substructures depend on both disc mass and evolutionary stage, independent of traditional SED-based classifications.
Our results show that Band 8 is an efficient tracer of disc substructures, recovering gaps and cavities even in optically thick regimes and with relatively short integration times. We find that prominent substructures are strongly associated with more massive discs (≳10 M⊕ of dust), while lower-mass discs largely appear smooth—though this may partly reflect current resolution limits.
In the final part of the talk, I will present new ALMA Band 1 (42 GHz; 7.5 mm) observations of the 15 brightest discs in our sample, obtained very recently. At these wavelengths, we trace millimeter-sized grains rather than sub-millimeter grains, allowing a direct comparison of disc morphology as a function of grain size. Notably, several discs exhibit distinct structures at Band 1 and Band 8, providing new insights into dust growth, radial drift, and particle trapping. These early Band 1 results highlight the power of multi-wavelength, high-resolution studies in disentangling the physical origins of disc substructures and advancing our understanding of planet formation across the full disc population.