Upper limits on protolunar disc masses using ALMA observations of directly-imaged exoplanets

Abstract

The Solar System gas giants are each surrounded by many moons, with at least 50 prograde satellites thought to have formed from circumplanetary material. Just like the Sun is not the only star surrounded by planets, extrasolar gas giants are likely surrounded by satellite systems. Here, we report on ALMA observations of four <40 Myr old stars with directly-imaged companions: PZ Tel, AB Pic, 51 Eri, and $\kappa$ And. Continuum emission at 1.3 mm is undetected for any of the systems. Since these are directly-imaged companions, there is knowledge of their temperatures, masses and locations. These allow for upper limits on the amount of circumplanetary dust to be derived from detailed radiative transfer models. These protolunar disc models consider two disc sizes: 0.4 and 0.04 times the exoplanet's Hill radius. The former is representative of hydrodynamic simulations of circumplanetary discs while the latter a case with significant radial drift of solids. The more compact case is also motivated by the semi-major axis of Callisto, enclosing Jupiter's Galilean satellites. All upper limits fall below the expected amount of dust required to explain regular satellite systems ($10^{-4}$ times the mass of their central planet). Upper limits are compared with viscous evolution and debris disc models. Our analysis suggests that the non detections can be interpreted as evidence of dust growth beyond metre sizes to form moonetesimals in timescales <10 Myr. This sample increases by 50% the number of ALMA non-detections of young companions available in the literature.

6 pages, 3 figures, accepted for publication in MNRAS

References in corpus (16)

• Direct Imaging of Multiple Planets Orbiting the Star HR 8799
• Seven temperate terrestrial planets around the nearby ultracool dwarf star TRAPPIST-1
• Astrophysics Source Code Library
• Formation of Regular Satellites from Ancient Massive Rings in the Solar System
• Modeling giant extrasolar ring systems in eclipse and the case of J1407b: sculpting by exomoons?
• Kuiper Belt-Like Hot and Cold Populations of Planetesimal Inclinations in the $\beta$ Pictoris Belt Revealed by ALMA
• Evidence for a circumplanetary disk around protoplanet PDS 70 b
• The evolution of photo-evaporating viscous discs in binaries
• An ALMA and MagAO Study of the Substellar Companion GQ Lup B
• ALMA 1.3 Millimeter Map of the HD 95086 System
• An ALMA Constraint on the GSC 6214-210 B Circum-Substellar Accretion Disk Mass
• ALMA Observations of the Young Substellar Binary System 2M1207
• New Extinction and Mass Estimates from Optical Photometry of the Very Low Mass Brown Dwarf Companion CT Chamaeleontis B with the Magellan AO System
• An Explanation of the Very Low Radio Flux of Young Planet-mass Companions
• An upper limit on the mass of the circumplanetary disk for DH Tau b
• VLA observations of the disk around the young brown dwarf 2MASS J044427+2512

Cited by in corpus (3)

• The search for disks or planetary objects around directly imaged companions: A candidate around DH Tau B
• Can close-in giant exoplanets preserve detectable moons?
• ALMA and NACO observations towards the young exoring transit system J1407 (V1400 Cen)