  SONYC -- Substellar Objects in Nearby Young Clusters -- is a program to
investigate the frequency and properties of young substellar objects with
masses down to a few times that of Jupiter. Here we present a census of very
low mass objects in the ~1 Myr old cluster NGC1333. We analyze near-infrared
spectra taken with FMOS/Subaru for 100 candidates from our deep, wide-field
survey and find 10 new likely brown dwarfs with spectral types of M6 or later.
Among them, there are three with >~M9 and one with early L spectral type,
corresponding to masses of 0.006 to <~0.02 Msol, so far the lowest mass objects
identified in this cluster. The combination of survey depth, spatial coverage,
and extensive spectroscopic follow-up makes NGC1333 one of the most
comprehensively surveyed clusters for substellar objects. In total, there are
now 51 objects with spectral type M5 or later and/or effective temperature of
3200 K or cooler identified in NGC1333; 30-40 of them are likely to be
substellar. NGC1333 harbours about half as many brown dwarfs as stars, which is
significantly more than in other well-studied star forming regions, thus
raising the possibility of environmental differences in the formation of
substellar objects. The brown dwarfs in NGC1333 are spatially strongly
clustered within a radius of ~1 pc, mirroring the distribution of the stars.
The disk fraction in the substellar regime is <66%, lower than for the total
population (83%) but comparable to the brown dwarf disk fraction in other 2-3
Myr old regions.
