Near-infrared H2 and Continuum Survey of Extended Green Objects. II.
  Complete Census for the Northern Galactic Plane
  We discuss 94 Extended Green Objects (EGOs) in the northern Galactic plane
cataloged by Cyganowski et al, based on near-infrared narrowband H2 (2.122
{\mu}m and continuum observations from the United Kingdom Infrared Telescope.
This data set is three times larger than our previous study, and is unbiased by
preselection. As discussed in the previous paper, the morphologies of the 4.5
{\mu}m emission generally resemble those of the near-infrared continuum, but
are different from those of the H2 emission. Of our sample, only 28% of EGOs
with H2 emission show similar morphologies between 4.5 {\mu}m and H2 emission.
These results suggest that the 4.5 {\mu}m emission mainly comes from scattered
continuum from the embedded young stellar object (YSO), and partially from H2
emission. About half of EGOs are associated with H2 outflows, if the H2 outflow
incompleteness is considered. The H2 outflow detection rate for EGOs with
K-band detections (61%) is significantly higher than for those without K-band
detections (36%). This difference may be due to the fact that both H2 and
K-band emissions are associated with outflows, i.e., H2 emission and K-band
continuum are associated with shocks and outflow cavities, respectively. We
also compared the correlation between the H2 outflows and Class I 44 GHz
methanol masers from literature. The methanol masers can be located upstream or
downstream of the H2 outflows and some bright H2 spots or outflows are not
associated with methanol masers, suggesting that methanol masers and H2
emission trace different excitation conditions.
