We present Atacama Large Millimeter/submillimeter Array 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 mu m continuum and CO J = 3-2 line emission with beam size similar to 0."3 (similar to 45 au) 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 an FWHM of 59 +/- 12 au, while the gas has a larger extent with a characteristic radius of 46.5 +/- 1.8 au. 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-circle dot, where d is a known distance, and determine that we view the disk at an inclination angle of 60 degrees 5 +/- 0 degrees 5 and a position angle of 346 degrees +/- 1 degrees. The 3s upper limit on the 870 mu m flux density of any circumplanetary disk associated with GQ Lup b of <0.15 mJy implies an upper limit on the dust disk mass of <0.04M(circle dot) 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.

We present ALMA mosaic observations at 1.3. mm (223 GHz) of the Fomalhaut system with a sensitivity of 14 mu Jy/beam. These observations provide the first millimeter map of the continuum dust emission from the complete outer debris disk with uniform sensitivity, enabling the first conclusive detection of apocenter glow. We adopt an MCMC modeling approach that accounts for the eccentric orbital parameters of a collection of particles within the disk. The outer belt is radially confined with an inner edge of 136.3 +/- 0.9. au and width of 13.5 +/- 1.8. au. We determine a best-fit eccentricity of 0.12 +/- 0.01. Assuming a size distribution power-law index of q. =. 3.46 +/- 0.09, we constrain the dust absorptivity power-law index a to be 0.9 <beta <. 1.5. The geometry of the disk is robustly constrained with inclination 65 degrees. 6 +/- 0 degrees. 3, position angle 337 degrees 9 +/- 0 degrees.3, and argument of periastron 22 degrees.5 +/- 4 degrees. 3. Our observations do not confirm any of the azimuthal features found in previous imaging studies of the disk with Hubble Space Telescope, SCUBA, and ALMA. However, we cannot rule out structures. 10 au in size or that only affect smaller grains. The central star is clearly detected with a flux density of 0.75 +/- 0.02. mJy, significantly lower than predicted by current photospheric models. We discuss the implications of these observations for the directly imaged Fomalhaut b and the inner dust belt detected at infrared wavelengths.

The mass of a protoplanetary disk limits the formation and future growth of any planet. Masses of protoplanetary disks are usually calculated from measurements of the dust continuum emission by assuming an interstellar gas-to-dust ratio. To investigate the utility of CO as an alternate probe of disk mass, we use ALMA to survey (CO)-C-13 and (CO)-O-18 J = 3-2 line emission from a sample of 93 protoplanetary disks around stars and brown dwarfs with masses from 0.03 to 2 M-circle dot in the nearby Chamaeleon I star-forming region. We detect (CO)-C-13 emission from 17 sources and (CO)-O-18 from only one source. Gas masses for disks are then estimated by comparing the CO line luminosities to results from published disk models that include CO freeze-out and isotope-selective photodissociation. Under the assumption of a typical interstellar medium CO-to-H-2 ratio of 10(-4), the resulting gas masses are implausibly low, with an average gas mass of similar to 0.05M(Jup) as inferred from the average flux of stacked (CO)-C-13 lines. The low gas masses and gas-to-dust ratios for Cha I disks are both consistent with similar results from disks in the Lupus star-forming region. The faint CO line emission may instead be explained if disks have much higher gas masses, but freeze-out of CO or complex C-bearing molecules is underestimated in disk models. The conversion of CO flux to CO gas mass also suffers from uncertainties in disk structures, which could affect gas temperatures. CO emission lines will only be a good tracer of the disk mass when models for C and CO depletion are confirmed to be accurate.

The disk mass is among the most important input parameter for every planet formation model to determine the number and masses of the planets that can form. We present an ALMA 887 mu m survey of the disk population around objects from similar to 2 to 0.03 M-circle dot in the nearby similar to 2 Myr old Chamaeleon I star-forming region. We detect thermal dust emission from 66 out of 93 disks, spatially resolve 34 of them, and identify two disks with large dust cavities of about 45 au in radius. Assuming isothermal and optically thin emission, we convert the 887 mu m flux densities into dust disk masses, hereafter M-dust. We find that the M-dust-M* relation is steeper than linear and of the form M-dust proportional to (M*)(1.3-1.9), where the range in the power-law index reflects two extremes of the possible relation between the average dust temperature and stellar luminosity. By reanalyzing all millimeter data available for nearby regions in a self-consistent way, we show that the 1-3 Myr old regions of Taurus, Lupus, and Chamaeleon. I share the same M-dust-M* relation, while the 10 Myr old Upper. Sco association has a steeper relation. Theoretical models of grain growth, drift, and fragmentation reproduce this trend and suggest that disks are in the fragmentation-limited regime. In this regime millimeter grains will be located closer in around lower-mass stars, a prediction that can be tested with deeper and higher spatial resolution ALMA observations.

Recent Atacama Large Millimeter/submillimeter Array observations present mounting evidence for the presence of exocometary gas released within Kuiper Belt analogs around nearby main-sequence stars. This represents a unique opportunity to study their ice reservoir at the younger ages when volatile delivery to planets is most likely to occur. We here present the detection of CO J=2-1 emission colocated with dust emission from the cometary belt in the 440 Myr old Fomalhaut system. Through spectrospatial filtering, we achieve a 5.4s detection and determine that the ring's sky-projected rotation axis matches that of the star. The CO mass derived (0.65-42) x10(-7) M-circle plus is the lowest of any circumstellar disk detected to date and must be of exocometary origin. Using a steady-state model, we estimate the CO+ CO2 mass fraction of exocomets around Fomalhaut to be between 4.6% and 76%, consistent with solar system comets and the two other belts known to host exocometary gas. This is the first indication of a similarity in cometary compositions across planetary systems that may be linked to their formation scenario and is consistent with direct interstellar medium inheritance. In addition, we find tentative evidence that(49 +/- 27)% of the detected flux originates from a region near the eccentric belt's pericenter. If confirmed, the latter may be explained through a recent impact event or CO pericenter glow due to exocometary release within a steady-state collisional cascade. In the latter scenario, we show how the azimuthal dependence of the CO release rate leads to asymmetries in gas observations of eccentric exocometary belts.