Filamentary Flows and Clump-fed High-mass Star Formation in G22
  G22 is a hub-filament system composed of four supercritical filaments.
Velocity gradients are detected along three filaments. A total mass infall rate
of 440 $M_\odot$~Myr$^{-1}$ would double the hub mass in about six free-fall
times. The most massive clump C1 would be in global collapse with an infall
velocity of 0.31 km s$^{-1}$ and a mass infall rate of $ 7.2\times10^{-4} $
$M_\odot$ yr$^{-1}$, which is supported by the prevalent HCO$^+$ (3-2) and
$^{13}$CO (3-2) blue profiles. A hot molecular core (SMA1) was revealed in C1.
At the SMA1 center, there is a massive protostar (MIR1) driving multipolar
outflows which are associated with clusters of class I methanol masers. MIR1
may be still growing with an accretion rate of $7\times10^{-5}$ $M_\odot$
yr$^{-1}$. Filamentary flows, clump-scale collapse, core-scale accretion
coexist in G22, suggesting that high-mass starless cores may not be
prerequisite to form high-mass stars. In the high-mass star formation process,
the central protostar, the core, and the clump can grow in mass simultaneously.
