Gaps and Rings: A Near-Universal Trait of Extended Protoplanetary Discs

TL;DR

This study reveals that nearly all extended protoplanetary discs exhibit substructures like rings and gaps, suggesting these features are a near-universal trait crucial for understanding dust evolution and planet formation.

Contribution

The paper provides high-resolution ALMA observations of 26 previously unresolved extended discs, demonstrating that substructures are nearly universal in such discs across multiple star-forming regions.

Findings

91% of extended discs show substructures

Substructures are more common in larger, massive discs

Structured discs tend to retain their dust mass over time

Abstract

Substructures such as rings, gaps, and cavities are commonly observed in protoplanetary discs and are thought to play a key role in dust evolution and planet formation. However, a fraction of the extended discs (68% dust radii > 30 AU) in nearby star-forming regions remain unresolved, leaving their substructure content uncertain and thereby limiting our understanding of dust evolution and the initial conditions for planet formation across the full disc population. We aim to investigate the presence of substructures in previously unresolved, extended discs to assess whether all extended protoplanetary discs in the Solar neighbourhood exhibit substructures. We present new high-resolution ($\sim$0.12") ALMA Band 6 continuum observations at 1.33 mm of 26 previously unresolved, extended discs within 200 pc, completing the high-resolution sample of extended discs in Taurus, Ophiuchus, Chamaeleon, Lupus, Upper Scorpius, Upper Centaurus-Lupus and Lower Centaurus-Crux. We analyse radial intensity profiles using Frankenstein and Galario to detect substructures. Seventeen discs show clear substructures, while nine appear compact and structureless, smooth or ambiguous due to inclination or possible binarity/late-stage infall. We detect $^{12}$CO J=2-1 emission in 15 discs, with extended emission in four. Combined with literature data, our complete sample of 730 protoplanetary discs reveals that nearly all extended discs exhibit substructures, $\sim$91% detected in the full sample, and up to $\sim$98% when correcting for high-inclination systems where substructures may be hidden. Substructures are a near-universal feature of extended protoplanetary discs. They are more commonly detected in larger, massive discs and around higher-mass stars, and structured discs retain their dust mass over time. This supports the scenario in which dust traps, possibly induced by giant planets, shape disc morphologies.