Triggered star formation surrounding Wolf-Rayet star HD 211853
  The environment surrounding Wolf-Rayet star HD 211853 is studied in molecular
emission, infrared emission, as well as radio and HI emission. The molecular
ring consists of well-separated cores, which have a volume density of 10$^{3}$
cm$^{-3}$ and kinematic temperature $\sim$20 K. Most of the cores are under
gravitational collapse due to external pressure from the surrounding ionized
gas. From SED modeling towards the young stellar objects (YSOs), sequential
star formation is revealed on a large scale in space spreading from the
Wolf-Rayet star to the molecular ring. A small scale sequential star formation
is revealed towards core A, which harbors a very young star cluster. Triggered
star formations is thus suggested. The presence of PDR, the fragmentation of
the molecular ring, the collapse of the cores, the large scale sequential star
formation indicate the "Collect and Collapse" process functions in this region.
The star forming activities in core A seem to be affected by the
"Radiation-Driven Implosion" (RDI) process.
