Mapping the Merging Zone of Late Infall in the AB Aur Planet-forming System

Abstract Late infall events challenge the traditional view that planet formation occurs without external influence. Here we present deep Atacama Large Millimeter/submillimeter Array 12 CO J = 2–1 and SO J N = 5 6 –4 5 observations toward AB Aurigae (AB Aur), a Class II disk system with strong signs of gravitational instability and ongoing planet formation. By applying Keplerian and anti-Keplerian masks, we separate disk-like and non-disk-like motions of 12 CO, considering the two outputs as the “disk” and “exo-disk” (out of disk) emission components, respectively. The disk component of 12 CO extends to ∼1600 au in radius and exhibits a stunningly rich architecture of global spiral structure. The exo-disk emission consists predominantly of three spiral structures—S1, S2, and S3—whose projections are cospatial with the disk. We successfully reproduce their trajectories with a ballistic accretion flow model, finding that S1 and S2 (both redshifted) are infalling toward the disk from in front, and S3 (blueshifted) is infalling from behind. Where the terminal ends of S1 and S2 become indistinguishable from the disk, we observe a brightness peak in SO emission 2.5× the azimuthal average of a background SO ring. This merging zone lies within a relatively confined region 15°–100 ∘ east of north, and between ∼150 and 300 au from the star, at scales relevant to where planet candidates have been previously identified. The AB Aur system provides a unified picture of late infall inducing replenishment of the disk, triggering gravitational instability, and modifying the conditions of forming planets.

Authors

Publication Details

Journal
The Astrophysical Journal Letters
Published
2025-03-06
DOI
https://doi.org/10.3847/2041-8213/adb7d5
Citations
18
Primary Topic
Stellar, planetary, and galactic studies
Type
article
Field-Weighted Citation Impact
20.79

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article

Mapping the Merging Zone of Late Infall in the AB Aur Planet-forming System

Giuseppe Lodato, Dominique Segura-Cox, Ruobing Dong, Teresa Paneque-Carreño et al.
18 citations
The Astrophysical Journal Letters
Stellar, planetary, and galactic studies
20.79
article

Mapping the Merging Zone of Late Infall in the AB Aur Planet-forming System

Giuseppe Lodato, Dominique Segura-Cox, Ruobing Dong, Teresa Paneque-Carreño, J. E. Pineda, Jun Hashimoto, Benedetta Veronesi, Jessica Speedie, Richard Teague, Cassandra Hall, Cristiano Longarini, Josh Calcino, Ya‐Wen Tang
article en
18 citations

Abstract

Abstract Late infall events challenge the traditional view that planet formation occurs without external influence. Here we present deep Atacama Large Millimeter/submillimeter Array 12 CO J = 2–1 and SO J N = 5 6 –4 5 observations toward AB Aurigae (AB Aur), a Class II disk system with strong signs of gravitational instability and ongoing planet formation. By applying Keplerian and anti-Keplerian masks, we separate disk-like and non-disk-like motions of 12 CO, considering the two outputs as the “disk” and “exo-disk” (out of disk) emission components, respectively. The disk component of 12 CO extends to ∼1600 au in radius and exhibits a stunningly rich architecture of global spiral structure. The exo-disk emission consists predominantly of three spiral structures—S1, S2, and S3—whose projections are cospatial with the disk. We successfully reproduce their trajectories with a ballistic accretion flow model, finding that S1 and S2 (both redshifted) are infalling toward the disk from in front, and S3 (blueshifted) is infalling from behind. Where the terminal ends of S1 and S2 become indistinguishable from the disk, we observe a brightness peak in SO emission 2.5× the azimuthal average of a background SO ring. This merging zone lies within a relatively confined region 15°–100 ∘ east of north, and between ∼150 and 300 au from the star, at scales relevant to where planet candidates have been previously identified. The AB Aur system provides a unified picture of late infall inducing replenishment of the disk, triggering gravitational instability, and modifying the conditions of forming planets.

The Astrophysical Journal LettersVol. 981(2)
National Science Foundation, National Aeronautics and Space Administration, Alfred P. Sloan Foundation, California Institute of Technology, Canadian Foundation for AIDS Research, Canarie, University of Lethbridge, Space Telescope Science Institute, National Radio Astronomy Observatory, Imperial College London, European Commission, University of Sussex, Cardiff University, National Natural Science Foundation of China, Centre National d’Etudes Spatiales, Università degli Studi di Padova, Korea Astronomy and Space Science Institute, KU Leuven, Centre National de la Recherche Scientifique, Bundesministerium für Verkehr, Innovation und Technologie, National Astronomical Observatory of Japan, National Science and Technology Council, Alliance de recherche numérique du Canada, Max-Planck-Institut für Astronomie, Centro de Estudos Ambientais e Marinhos, Universidade de Aveiro, Observatoire de Paris, Université de Recherche Paris Sciences et Lettres, Canadian Space Agency, Natural Sciences and Engineering Research Council of Canada, Science and Technology Facilities Council, Japan Society for the Promotion of Science, National Institutes of Natural Sciences, National Astronomical Observatories, Chinese Academy of Sciences
Openalex Percentile: Top 1%
Stellar, planetary, and galactic studies
20.79
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