Molecules with ALMA at Planet-forming Scales (MAPS): A Circumplanetary Disk Candidate in Molecular-line Emission in the AS 209 Disk

• Published in: Astrophysical journal. Letters Vol. 934; no. 2; p. L20
• Main Authors: Bae, Jaehan, Teague, Richard, Andrews, Sean M., Benisty, Myriam, Facchini, Stefano, Galloway-Sprietsma, Maria, Loomis, Ryan A., Aikawa, Yuri, Alarcón, Felipe, Bergin, Edwin, Bergner, Jennifer B., Booth, Alice S., Cataldi, Gianni, Cleeves, L. Ilsedore, Czekala, Ian, Guzmán, Viviana V., Huang, Jane, Ilee, John D., Kurtovic, Nicolas T., Law, Charles J., Gal, Romane Le, Liu, Yao, Long, Feng, Ménard, François, Öberg, Karin I., Pérez, Laura M., Qi, Chunhua, Schwarz, Kamber R., Sierra, Anibal, Walsh, Catherine, Wilner, David J., Zhang, Ke
• Format: Journal Article
• Language: English
• Published: Austin The American Astronomical Society 01-08-2022; IOP Publishing; Bristol : IOP Publishing
• Subjects: Accretion disks; Annular gaps; Astrochemistry; Astrophysics; Continuum radiation; Deposition; Dust; Emissions; Exoplanet formation; Extrasolar planets; Flux density; Gas temperature; Gravitational instability; Lunar dust; Millimeter astronomy; Perturbation; Planet formation; Planetary orbits; Planets; Point sources; Protoplanetary disks; Radio interferometry; Sciences of the Universe; Submillimeter astronomy; T Tauri stars; Protoplanetary disks; Submillimeter astronomy; Planet formation; Astrophysics - Earth and Planetary Astrophysics; Radio interferometry; Millimeter astronomy; Exoplanet formation; Astrophysics - Solar and Stellar Astrophysics
• ISSN: 2041-8205; 2041-8213
• DOI: 10.3847/2041-8213/ac7fa3

We report the discovery of a circumplanetary disk (CPD) candidate embedded in the circumstellar disk of the T Tauri star AS 209 at a radial distance of about 200 au (on-sky separation of 1.″4 from the star at a position angle of 161°), isolated via
13
CO
J
= 2−1 emission. This is the first instance of CPD detection via gaseous emission capable of tracing the overall CPD mass. The CPD is spatially unresolved with a 117 × 82 mas beam and manifests as a point source in
13
CO, indicating that its diameter is ≲14 au. The CPD is embedded within an annular gap in the circumstellar disk previously identified using
12
CO and near-infrared scattered-light observations and is associated with localized velocity perturbations in
12
CO. The coincidence of these features suggests that they have a common origin: an embedded giant planet. We use the
13
CO intensity to constrain the CPD gas temperature and mass. We find that the CPD temperature is ≳35 K, higher than the circumstellar disk temperature at the radial location of the CPD, 22 K, suggesting that heating sources localized to the CPD must be present. The CPD gas mass is ≳0.095
M
Jup
≃ 30
M
⊕
adopting a standard
13
CO abundance. From the nondetection of millimeter continuum emission at the location of the CPD (3
σ
flux density ≲26.4
μ
Jy), we infer that the CPD dust mass is ≲0.027
M
⊕
≃ 2.2 lunar masses, indicating a low dust-to-gas mass ratio of ≲9 × 10
−4
. We discuss the formation mechanism of the CPD-hosting giant planet on a wide orbit in the framework of gravitational instability and pebble accretion.