Discovery of an extremely wide-angle bipolar outflow in AFGL 5142
  Most bipolar outflows are associated with individual young stellar objects
and have small opening angles. Here we report the discovery of an extremely
wide-angle ($\sim$180$\arcdeg$) bipolar outflow ("EWBO") in a cluster forming
region AFGL 5142 from low-velocity emission of the HCN (3-2) and HCO$^{+}$
(3-2) lines. This bipolar outflow is along a north-west to south-east direction
with a line-of-sight flow velocity of about 3 km~s$^{-1}$ and is spatially
connected to the high-velocity jet-like outflows. It seems to be a collection
of low-velocity material entrained by the high-velocity outflows due to
momentum feedback. The total ejected mass and mass loss rate due to both high
velocity jet-like outflows and the "EWBO" are $\sim$24.5 M$_{\sun}$ and
$\sim1.7\times10^{-3}$ M$_{\sun}$~yr$^{-1}$, respectively. Global collapse of
the clump is revealed by the "blue profile" in the HCO$^{+}$ (1-0) line. A
hierarchical network of filaments was identified in NH$_{3}$ (1,1) emission.
Clear velocity gradients of the order of 10 km~s$^{-1}$~pc$^{-1}$ are found
along filaments, indicating gas inflow along the filaments. The sum of the
accretion rate along filaments and mass infall rate along the line of sight is
$\sim$3.1$\times10^{-3}$ M$_{\sun}$~yr$^{-1}$, which exceeds the total mass
loss rate, indicating that the central cluster is probably still gaining mass.
The central cluster is highly fragmented and 22 condensations are identified in
1.1 mm continuum emission. The fragmentation process seems to be determined by
thermal pressure and turbulence. The magnetic field may not play an important
role in fragmentation.
