ALMA Measurements of Circumstellar Material in the GQ Lup System
MacGregor et al
We present ALMA observations of the GQ Lup system, a young Sun-like star with a substellar mass companion in a wide-separation orbit. These observations of 870
μm continuum and CO J=3-2 line emission with beam size ∼0.3″( ∼45AU) resolve the disk of dust and gas surrounding the primary star, GQ Lup A, and provide deep limits on any circumplanetary disk surrounding the companion, GQ Lup b. The circumprimary dust disk is compact with a FWHM of 59±12AU, while the gas has a larger extent with a characteristic radius of 46.5±1.8AU. By forward-modeling the velocity field of the circumprimary disk based on the CO emission, we constrain the mass of GQ Lup A to be M∗=(1.03±0.05)∗(d/156 pc) M⊙, where dis a known distance, and determine that we view the disk at an inclination angle of 60.5∘±0.5∘and a position angle of 346∘±1∘. The 3σupper limit on the 870 μm flux density of any circumplanetary disk associated with GQ Lup b of <0.15mJy implies an upper limit on the dust disk mass of <0.04 M⊕for standard assumptions about optically thin emission. We discuss proposed mechanisms for the formation of wide-separation substellar companions given the non-detection of circumplanetary disks around GQ Lup b and other similar systems.