Gas infall in the massive star formation core G192.16-3.84
  Previous observations have revealed an accretion disk and outflow motion in
high-mass star-forming region G192.16-3.84. While collapse have not been
reported before. We present here molecular line and continuum observations
toward massive core G192.16-3.84 with the Submillimeter Array. C$^{18}$O(2-1)
and HCO$^{+}$(3-2) lines show pronounced blue profiles, indicating gas
infalling in this region. This is the first time that the infall motion has
been reported in G192.16-3.84 core. Two-layer model fitting gave infall
velocities of 2.0$\pm$0.2 and 2.8$\pm$0.1 km s$^{-1}$. Assuming that the cloud
core follows a power-law density profile ($\rho$$\propto$$r^{1.5}$), the
corresponding mass infall rates are (4.7$\pm$1.7)$\times10^{-3}$ and
(6.6$\pm$2.1)$\times10^{-3}$ M$_{\sun}$ yr$^{-1}$ for C$^{18}$O(2-1) and
HCO$^{+}$(3-2), respectively. The derived infall rates are in agreement with
the turbulent core model and those in other high-mass star-forming regions,
suggesting that high accretion rate is a general requirement to form a massive
star.
