  In the QGP motivated threshold model, in addition to the normal nuclear
absorption, $J/\psi$'s are subjected to an additional "anomalous" suppression.
We have analysed the recently published PHENIX data on the participant number
dependence of the nuclear modification factor for $J/\psi$'s in Au+Au
collisions and extracted the anomalous suppression required to explain the
data. At mid rapidity $J/\psi$'s are anomalously suppressed only above a
threshold density $n_c$=3.73 fm$^{-2}$. The forward rapidity data on the
otherhand require that $J/\psi$'s are continuously "anomalously" suppressed.
The analysis strongly indicate that in mid rapidity $J/\psi$'s are suppressed
in a deconfined medium. Using the PHENIX data on the participant number
dependence of the Bjorken energy density, we have also estimated the QGP
formation time. For critical temperature $T_c$=192 MeV, estimated QGP formation
time ranges between 0.06-0.08 fm/c.
