Abstract
Abstract Characterizing the physical properties and compositions of circumplanetary disks can provide important insights into the formation of giant planets and satellites. We report Atacama Large Millimeter/submillimeter Array 0.88 mm (Band 7) continuum observations of six planetary-mass (10–20 M Jup) companions: CT Cha b, 1RXS 1609 b, ROXs 12 b, ROXs 42B b, DH Tau b, and FU Tau b. No continuum sources are detected at the locations of the companions down to 3σ limits of 120–210 μJy. Given these nondetections, it is not clear whether disks around planetary-mass companions indeed follow the disk-flux–host-mass trend in the stellar regime. The faint radio brightness of these companion disks may result from a combination of fast radial drift and a lack of dust traps. Alternatively, as disks in binary systems are known to have significantly lower millimeter fluxes due to tidal interactions, these companion disks may instead follow the relationship of moderate-separation binary stars. This scenario can be tested with sensitive continuum imaging at rms levels of ≲10 μJy.
Highlights
Analogous to circumstellar disks, circumplanetary disks regulate mass accretion and angular momentum transport as giant planets form, thereby determining the formation timescale, temperature, luminosity, and terminal spin velocity of giant planets (e.g., Eisner 2015; Zhu 2015; Szulágyi & Mordasini 2017; Batygin 2018; Bryan et al 2018)
Characterizing circumplanetary disks helps reveal the physical mechanisms involved in giant planet formation as well as the initial conditions and bulk composition of exomoons, providing insight into similar processes that occurred for giant planets in the early solar system (e.g., Stamatellos & Herczeg 2015; Szulágyi et al 2017, 2018a; Drażkowska & Szulágyi 2018)
Circumplanetary disks inside gapped protoplanetary disks are expected to be detectable with the Atacama Large Millimeter/submillimeter Array (ALMA) across a range of millimeter and submillimeter wavelengths (e.g., Zhu et al 2016, 2018; Szulágyi et al 2018b), and recently the first such tentative detections have been reported around PDS 70 (Isella et al 2019)
Summary
Circumplanetary disks regulate mass accretion and angular momentum transport as giant planets form, thereby determining the formation timescale, temperature, luminosity, and terminal spin velocity of giant planets (e.g., Eisner 2015; Zhu 2015; Szulágyi & Mordasini 2017; Batygin 2018; Bryan et al 2018). While binary-like formation, such as prestellar core collapse (Low & Lynden-Bell 1976) or disk fragmentation (e.g., Kratter et al 2010), is often invoked to explain their existence, the bottomheavy mass distribution of PMCs may imply that they are. Resolved dust and gas observations of PMC disks may reveal substructures that could be linked to exomoons, and allow direct dynamical mass measurements which would enable tests of evolutionary models in the planet-mass regime. We present ALMA 0.88 mm (Band 7) observations of six PMCs (CT Cha b, 1RXS J160929.1–210524 b, ROXs 12 b, ROXs 42B b, DH Tau b, and FU Tau b) and discuss the implications
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