A Census of Young Stars and Brown Dwarfs in IC 348 and NGC 1333
  We have obtained optical and near-infrared spectra of candidate members of
the star-forming clusters IC 348 and NGC 1333. We classify 100 and 42
candidates as new members of the clusters, respectively, which brings the total
numbers of known members to 478 and 203. We also have performed spectroscopy on
a large majority of the previously known members of NGC 1333 in order to
provide spectral classifications that are measured with the same scheme that
has been applied to IC 348 in previous studies. The new census of members is
nearly complete for Ks<16.8 at Aj<1.5 in IC 348 and for Ks<16.2 at Aj<3 in NGC
1333, which correspond to masses of <=0.01 Msun for ages of 3 Myr according to
theoretical evolutionary models. The faintest known members extend below these
completeness limits and appear to have masses of ~0.005 Msun. In
extinction-limited samples of cluster members, NGC 1333 exhibits a higher
abundance of objects at lower masses than IC 348. It would be surprising if the
initial mass functions of these clusters differ significantly given their
similar stellar densities and formation environments. Instead, it is possible
that average extinctions are lower for less massive members of star-forming
clusters, in which case extinction-limited samples could be biased in favor of
low-mass objects in the more heavily embedded clusters like NGC 1333. In the
H-R diagram, the median sequences of IC 348 and NGC 1333 coincide with each
other for the adopted distances of 300 and 235 pc, which would suggest that
they have similar ages. However, NGC 1333 is widely believed to be younger than
IC 348 based on its higher abundance of disks and protostars and its greater
obscuration. Errors in the adopted distances may be responsible for this
discrepancy.
