Dust masses of young disks: constraining the initial solid reservoir for
  planet formation
  In recent years evidence has been building that planet formation starts
early, in the first $\sim$ 0.5 Myr. Studying the dust masses available in young
disks enables understanding the origin of planetary systems since mature disks
are lacking the solid material necessary to reproduce the observed exoplanetary
systems, especially the massive ones. 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. We use Atacama Large
Millimeter/submillimeter Array (ALMA) Band 6 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. Using the DIANA opacity model including large grains, with a dust
opacity value of $\kappa_{\rm 9\ mm}$ = 0.28 cm$^{2}$ g$^{-1}$, the median dust
masses of the embedded disks in Perseus are 158 M$_\oplus$ for Class 0 and 52
M$_\oplus$ for Class I from the VLA fluxes. The lower limits on the median
masses from ALMA fluxes are 47 M$_\oplus$ and 12 M$_\oplus$ for Class 0 and
Class I, respectively, obtained using the maximum dust opacity value
$\kappa_{\rm 1.3mm}$ = 2.3 cm$^{2}$ g$^{-1}$. The dust masses of young Class 0
and I disks are larger by at least a factor of 10 and 3, respectively, compared
with dust masses inferred for Class II disks in Lupus and other regions. 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 $\sim$ 15%. Higher efficiency of $\sim$ 30% is necessary if the
planet formation is set to start in Class I disks.
