Confronting Outflow-Regulated Cluster Formation Model with Observations
  Protostellar outflows have been shown theoretically to be capable of
maintaining supersonic turbulence in cluster-forming clumps and keeping the
star formation rate per free-fall time as low as a few percent. We aim to test
two basic predictions of this outflow-regulated cluster formation model, namely
(1) the clump should be close to virial equilibrium and (2) the turbulence
dissipation rate should be balanced by the outflow momentum injection rate,
using recent outflow surveys toward 8 nearby cluster-forming clumps (B59,
L1551, L1641N, Serpens Main Cloud, Serpens South, $\rho$ Oph, IC 348, and NGC
1333). We find, for almost all sources, that the clumps are close to virial
equilibrium and the outflow momentum injection rate exceeds the turbulence
momentum dissipation rate. In addition, the outflow kinetic energy is
significantly smaller than the clump gravitational energy for intermediate and
massive clumps with $M_{\rm cl} \gtrsim {\rm a \ few} \times 10^2 M_\odot$,
suggesting that the outflow feedback is not enough to disperse the clump as a
whole. The number of observed protostars also indicates that the star formation
rate per free-fall time is as small as a few percent for all clumps. These
observationally-based results strengthen the case for outflow-regulated cluster
formation.
