Star formation activity beyond the outer Arm I: WISE-selected candidate
  star-forming regions
  The outer Galaxy beyond the Outer Arm provides a good opportunity to study
star formation in an environment significantly different from that in the solar
neighborhood. However, star-forming regions in the outer Galaxy have never been
comprehensively studied or cataloged because of the difficulties in detecting
them at such large distances. We studied 33 known young star-forming regions
associated with 13 molecular clouds at $R_{\rm G}$ $\ge$ 13.5 kpc in the outer
Galaxy with data from the Wide-field Infrared Survey Explorer (WISE)
mid-infrared all-sky survey. From their color distribution, we developed a
simple identification criterion of star-forming regions in the outer Galaxy
with the WISE color. We applied the criterion to all the WISE sources in the
molecular clouds in the outer Galaxy at $R_{\rm G}$ $\ge$ 13.5 kpc detected
with the Five College Radio Astronomy Observatory (FCRAO) $^{12}$CO survey of
the outer Galaxy, of which the survey region is 102$^\circ$.49 $\le$ $l$ $\le$
141$^\circ$.54, $-$3$^\circ$.03 $\le$ $b$ $\le$ 5$^\circ$.41, and successfully
identified 711 new candidate star-forming regions in 240 molecular clouds. The
large number of samples enables us to perform the statistical study of
star-formation properties in the outer Galaxy for the first time. This study is
crucial to investigate the fundamental star-formation properties, including
star-formation rate, star-formation efficiency, and initial mass function, in a
primordial environment such as the early phase of the Galaxy formation.
