A high-resolution survey of protoplanetary disks in Lupus and the nature of compact disks (2503.19504v1)

Abstract: Most of the exoplanets discovered in our galaxy to date orbit low-mass stars, which tend to host small disks in their early stages. To better elucidate the link between planet formation and disk substructures, observational biases should be reduced through observations of these small, faint disks at the highest resolution using the Atacama Large Millimeter Array (ALMA). In this work, we present new high-resolution (0.03-0.04") ALMA observations at 1.3 mm of 33 disks located in the Lupus star-forming region. Combining archival data and previously published work, we provide a near-complete high resolution image library of 73 protoplanetary (Class II) disks in Lupus. This enable us to measure dust disk radii down to a limit of 0.6 au and analyze intensity profiles using visibility modeling. We show that 67% of Lupus protoplanetary disks have dust radii smaller than 30 au, with new substructures detected in 11, showing some of the shortest separation gaps. The size-luminosity relation in Lupus aligns well with a drift-dominated dust evolution scenario and, for the most compact disks (< 30 au), we found dust masses ranging from 0.3 to 26.3 Earth masses. Assuming that the detected substructures were dynamical effects of planets, we estimated the planet masses to range from 20 to 2000 Earth masses with separations between 2 to 74 au. Our results indicate that two-thirds of the protoplanetary disks in Lupus are smooth, and compact, with substructures being more prominent in the few larger disks. These compact disks are consistent with drift-dominated evolution, with their masses and optical depths suggesting that they may have already experienced some planet formation, with most of the small solids converted into planetesimals and planets. This makes them prime candidates, for explaining the formation and origin of super-Earths. [Abridged]

A High-Resolution Survey of Protoplanetary Disks in Lupus and the Nature of Compact Disks

The paper "A high-resolution survey of protoplanetary disks in Lupus and the nature of compact disks" by Guerra-Alvarado et al. presents an extensive high-resolution survey of protoplanetary disks in the Lupus star-forming region using the Atacama Large Millimeter Array (ALMA). This work focuses on understanding the properties and evolution of small, compact disks, which is essential for elucidating the relationship between disk substructures and planet formation in low-mass star environments.

The authors conducted high-resolution (0.03-0.04'') ALMA observations of 33 disks with dust continuum fluxes below 25 mJy in the Lupus region at a wavelength of 1.3 mm. This dataset, combined with existing archives and previous observations, provides a near-complete image library of 73 Class II protoplanetary disks.

Key Findings and Methodology

1. Dust Disk Radii Measurement:
   • The paper finds that 67% of the Lupus protoplanetary disks possess dust radii smaller than 30 astronomical units (au). This confirms the prevalence of compact disks in low-mass star systems.
2. Substructure Characterization:
   • New substructures were identified in 11 disks with especially tight separation gaps, emphasizing the importance of high-resolution imaging to discern finer disk features that might be pivotal in planet formation scenarios.
3. Size-Luminosity Relationship:
   • The size-luminosity relation, when accounting for smaller disks, supports a drift-dominated dust evolution scenario. This suggests that dust particles in these disks grow and migrate inward significantly, possibly influenced by external pressures or forming planets.
4. Radial Drift and Disk Masses:
   • For compact disks less than 30 au in radius, the paper compares measured sizes and fluxes to a grid of radiative transfer models to deduce the millimeter-emitting dust masses, which range from 0.3 to 26.3 M$_{\oplus}$. The estimates of dynamically influencing planet masses within these structures span 20-2000 M$_{\oplus}$ at separations from 2 to 74 au.

Implications and Future Prospects

The implications of this paper are significant for our understanding of planet formation in small disks, particularly those surrounding low-mass stars. The compact nature and, in some cases, the smoothness of these disks imply that much of the solid material may have already been converted into planetesimals or planets, making them prime candidates for studying the origins of super-Earths.

The observed alignment with drift-dominated evolution models indicates that further theoretical work is warranted to explore why certain disks develop prominent substructures while others remain largely featureless. Moreover, the estimation of planet masses in connection with disk substructures provides a valuable method for predicting the characteristics of forming planetary systems.

Future research is likely to focus on improving the resolution and sensitivity of observations to detect even smaller substructures and bridge the gap between the smallest observed protoplanetary disks and exoplanet statistics. Additionally, incorporating high-resolution gas observations could further inform our understanding of the formation and evolution of both disks and the planets forming within them.

Conclusively, this survey sets a new benchmark for the paper of protoplanetary disks in star-forming regions, emphasizing the role of high-resolution observations in unraveling the complex processes driving planet formation in compact disk environments.