A SiO J = 5 - 4 Survey Toward Massive Star Formation Regions
  We performed a survey in the SiO $J=5\rightarrow4$ line toward a sample of
199 Galactic massive star-forming regions at different evolutionary stages with
the SMT 10 m and CSO 10.4 m telescopes. The sample consists of 44 infrared dark
clouds (IRDCs), 86 protostellar candidates, and 69 young \HII\ regions. We
detected SiO $J=5\rightarrow4$ line emission in 102 sources, with a detection
rate of 57\%, 37\%, and 65\% for IRDCs, protostellar candidates, and young
\HII\ regions, respectively. We find both broad line with Full Widths at Zero
Power (FWZP) $>$ 20 \kms and narrow line emissons of SiO in objects at various
evolutionary stages, likely associated with high-velocity shocks and
low-velocity shocks, respectively. The SiO luminosities do not show apparent
differences among various evolutionary stages in our sample. We find no
correlation between the SiO abundance and the luminosity-to-mass ratio,
indicating that the SiO abundance does not vary significantly in regions at
different evolutionary stages of star formation.
