We present the first high-resolution sub-mm survey of both dust and gas for a large population of protoplanetary disks. Characterizing fundamental properties of protoplanetary disks on a statistical level is critical to understanding how disks evolve into the diverse exoplanet population. We use ALMA to survey 89 protoplanetary disks around stars with M * > 0.1 M in the young (1-3 Myr), nearby (150-200 pc) Lupus complex. Our observations cover the 890 µm continuum and the 13 CO and C 18 O 3-2 lines. We use the sub-mm continuum to constrain M dust to a few Martian masses (0.2-0.4 M ⊕ ) and the CO isotopologue lines to constrain M gas to roughly a Jupiter mass (assuming ISM-like [CO]/[H 2 ] abundance). Of 89 sources, we detect 62 in continuum, 36 in 13 CO, and 11 in C 18 O at > 3σ significance. Stacking individually undetected sources limits their average dust mass to 6 Lunar masses (0.03 M ⊕ ), indicating rapid evolution once disk clearing begins. We find a positive correlation between M dust and M * , and present the first evidence for a positive correlation between M gas and M * , which may explain the dependence of giant planet frequency on host star mass. The mean dust mass in Lupus is 3× higher than in Upper Sco, while the dust mass distributions in Lupus and Taurus are statistically indistinguishable. Most detected disks have M gas 1 M Jup and gas-to-dust ratios < 100, assuming ISM-like [CO]/[H 2 ] abundance; unless CO is very depleted, the inferred gas depletion indicates that planet formation is well underway by a few Myr and may explain the unexpected prevalence of super-Earths in the exoplanet population.

Context. Recent years have seen building evidence that planet formation starts early, in the first ~0.5 Myr. Studying the dust masses available in young disks enables us to understand the origin of planetary systems given that mature disks are lacking the solid material necessary to reproduce the observed exoplanetary systems, especially the massive ones. Aims. We aim to determine if disks in the embedded stage of star formation contain enough dust to explain the solid content of the most massive exoplanets. Methods. We use Atacama Large Millimeter/submillimeter Array (ALMA) Band 6 (1.1–1.3 mm) continuum observations of embedded disks in the Perseus star-forming region together with Very Large Array (VLA) Ka-band (9 mm) data to provide a robust estimate of dust disk masses from the flux densities measured in the image plane. Results. We find a strong linear correlation between the ALMA and VLA fluxes, demonstrating that emission at both wavelengths is dominated by dust emission. For a subsample of optically thin sources, we find a median spectral index of 2.5 from which we derive the dust opacity index β = 0.5, suggesting significant dust growth. Comparison with ALMA surveys of Orion shows that the Class I dust disk mass distribution between the two regions is similar, but that the Class 0 disks are more massive in Perseus than those in Orion. Using the DIANA opacity model including large grains, with a dust opacity value of κ9 mm = 0.28 cm2 g−1, the median dust masses of the embedded disks in Perseus are 158 M⊕ for Class 0 and 52 M⊕ for Class I from the VLA fluxes. The lower limits on the median masses from ALMA fluxes are 47 M⊕ and 12 M⊕ for Class 0 and Class I, respectively, obtained using the maximum dust opacity value κ1.3 mm = 2.3 cm2 g−1. The dust masses of young Class 0 and I disks are larger by at least a factor of ten and three, respectively, compared with dust masses inferred for Class II disks in Lupus and other regions. Conclusions. The dust masses of Class 0 and I disks in Perseus derived from the VLA data are high enough to produce the observed exoplanet systems with efficiencies acceptable by planet formation models: the solid content in observed giant exoplanets can be explained if planet formation starts in Class 0 phase with an efficiency of ~15%. A higher efficiency of ~30% is necessary if the planet formation is set to start in Class I disks.

Understanding disk evolution and dissipation is essential for studies of planet formation. Transition disks, i.e., disks with large dust cavities and gaps, are promising candidates of active evolution. About two dozen candidates, selected by their spectral energy distribution (SED), have been confirmed to have dust cavities through millimeter interferometric imaging, but this sample is biased toward the brightest disks. The Spitzer surveys of nearby low-mass star-forming regions have resulted in more than 4000 young stellar objects. Using color criteria, we selected a sample of ∼150 candidates and an additional 40 candidates and known transition disks from the literature. The Spitzer data were complemented by new observations at longer wavelengths, including new JCMT and APEX submillimeter photometry, and WISE and Herschel-PACS mid-and far-infrared photometry. Furthermore, optical spectroscopy was obtained and stellar types were derived for 85% of the sample, including information from the literature. The SEDs were fit to a grid of RADMC-3D disk models with a limited number of parameters: disk mass, inner disk mass, scale height and flaring, and disk cavity radius, where the latter is the main parameter of interest. About 72% of our targets possibly have dust cavities based on the SED. The derived cavity sizes are consistent with imaging/modeling results in the literature, where available. Trends are found with L disk over L * ratio and stellar mass and a possible connection with exoplanet orbital radii. A comparison with a previous study where color observables are used reveals large overlap between their category of planet-forming disks and our transition disks with cavities. A large number of the new transition disk candidates are suitable for follow-up observations with ALMA.

Context. The mass evolution of protoplanetary disks is driven by both internal processes, and external factors, such as photoevaporation. Disentangling these two effects, however, has remained difficult. Aims. We measure the dust masses of a sample of 132 disks in the Orion Molecular Cloud (OMC)-2 region, and compare them to (i) externally photoevaporated disks in the Trapezium cluster, and (ii) disks in nearby low-mass star forming regions (SFRs). This allows us to test if initial disk properties are the same in high-and low-mass SFRs, and enables a direct measurement of the effect of external photoevaporation on disks. Methods. A ∼ 20 × 4 mosaic of 3 mm continuum observations from the Atacama Large Millimeter/submillimeter Array (ALMA) was used to measure the fluxes of 132 disks and 35 protostars > 0.5 pc away from the Trapezium. We identify and characterize a sample of 34 point sources not included in the Spitzer catalog on which the sample is based. Results. Of the disks, 37 (28%) are detected, with masses ranging from 7 − 270 M ⊕ . The detection rate for protostars is higher, at 69%. Disks near the Trapezium are found to be less massive by a factor 0.18 +0.18 −0.11 , implying a mass loss rate of 8 × 10 −8 M yr −1 . Conclusions. Our observations allow us to distinguish the impact of time and environment on disk evolution in a single SFR. The disk mass distribution in OMC-2 is statistically indistinguishable from that in nearby low-mass SFRs, like Lupus and Taurus. We conclude that age is the main factor determining the evolution of these disks. This result is robust with respect to assumptions of dust temperature, sample incompleteness and biases. The difference between the OMC-2 and Trapezium cluster samples is consistent with mass loss driven by far-ultraviolet radiation near the Trapezium. Together, this implies that in isolation, disk formation and evolution proceed similarly, regardless of cloud mass.

Context. Protoplanetary disks in dense, massive star-forming regions are strongly affected by their environment. How this environmental impact changes over time is an important constraint on disk evolution and external photoevaporation models. Aims. We characterize the dust emission from 179 disks in the core of the young (0.5 Myr) NGC 2024 cluster. By studying how the disk mass varies within the cluster, and comparing these disks to those in other regions, we aim to determine how external photoevaporation influences disk properties over time. Methods. Using the Atacama Large Millimeter/submillimeter Array, a 2.9′× 2.9′ mosaic centered on NGC 2024 FIR 3 was observed at 225 GHz with a resolution of 0.25″, or ~100 AU. The imaged region contains 179 disks identified at IR wavelengths, seven new disk candidates, and several protostars. Results. The overall detection rate of disks is 32 ± 4%. Few of the disks are resolved, with the exception of a giant (R = 300 AU) transition disk. Serendipitously, we observe a millimeter flare from an X-ray bright young stellar object (YSO), and resolve continuum emission from a Class 0 YSO in the FIR 3 core. Two distinct disk populations are present: a more massive one in the east, along the dense molecular ridge hosting the FIR 1-5 YSOs, with a detection rate of 45 ± 7%. In the western population, towards IRS 1, only 15 ± 4% of disks are detected. Conclusions. NGC 2024 hosts two distinct disk populations. Disks along the dense molecular ridge are young (0.2–0.5 Myr) and partly shielded from the far ultraviolet radiation of IRS 2b; their masses are similar to isolated 1–3 Myr old SFRs. The western population is older and at lower extinctions, and may be affected by external photoevaporation from both IRS 1 and IRS 2b. However, it is possible these disks had lower masses to begin with.