The VLA/ALMA Nascent Disk and Multiplicity (VANDAM) Survey of Orion
  Protostars. A Statistical Characterization of Class 0 and I Protostellar
  Disks
  We have conducted a survey of 328 protostars in the Orion molecular clouds
with ALMA at 0.87 mm at a resolution of $\sim$0.1" (40 au), including
observations with the VLA at 9 mm toward 148 protostars at a resolution of
$\sim$0.08" (32 au). This is the largest multi-wavelength survey of protostars
at this resolution by an order of magnitude. We use the dust continuum emission
at 0.87 mm and 9 mm to measure the dust disk radii and masses toward the Class
0, Class I, and Flat Spectrum protostars, characterizing the evolution of these
disk properties in the protostellar phase. The mean dust disk radii for the
Class 0, Class I, and Flat Spectrum protostars are 44.9$^{+5.8}_{-3.4}$,
37.0$^{+4.9}_{-3.0}$, and 28.5$^{+3.7}_{-2.3}$ au, respectively, and the mean
protostellar dust disk masses are 25.9$^{+7.7}_{-4.0}$, 14.9$^{+3.8}_{-2.2}$,
11.6$^{+3.5}_{-1.9}$ Earth masses, respectively. The decrease in dust disk
masses is expected from disk evolution and accretion, but the decrease in disk
radii may point to the initial conditions of star formation not leading to the
systematic growth of disk radii or that radial drift is keeping the dust disk
sizes small. At least 146 protostellar disks (35% out of 379 detected 0.87 mm
continuum sources plus 42 non-detections) have disk radii greater than 50 au in
our sample. These properties are not found to vary significantly between
different regions within Orion. The protostellar dust disk mass distributions
are systematically larger than that of Class II disks by a factor of $>$4,
providing evidence that the cores of giant planets may need to at least begin
their formation during the protostellar phase.
