Testing Models of Triggered Star Formation with Young Stellar Objects in
  Cepheus OB4
  OB associations are home to newly formed massive stars, whose turbulent winds
and ionizing flux create H II regions rich with star formation. Studying the
distribution and abundance of young stellar objects (YSOs) in these ionized
bubbles can provide essential insight into the physical processes that shape
their formation, allowing us to test competing models of star formation. In
this work, we examined one such OB association, Cepheus OB4 (Cep OB4) - a
well-suited region for studying YSOs due to its Galactic location, proximity,
and geometry. We created a photometric catalog from Spitzer/IRAC mosaics in
bands 1 (3.6 $\mu$m) and 2 (4.5 $\mu$m). We supplemented the catalog with
photometry from WISE, 2MASS, IRAC bands 3 (5.8 $\mu$m) and 4 (8.0 $\mu$m), MIPS
24 $\mu$m, and MMIRS near IR data. We used color-color selections to identify
821 YSOs, which we classified using the IR slope of the YSOs' spectral energy
distributions (SEDs), finding 67 Class I, 103 flat spectrum, 569 Class II, and
82 Class III YSOs. We conducted a clustering analysis of the Cep OB4 YSOs and
fit their SEDs. We found many young Class I objects distributed in the
surrounding shell and pillars as well as a relative age gradient of unclustered
sources, with YSOs generally decreasing in age with distance from the central
cluster. Both of these results indicate that the expansion of the H II region
may have triggered star formation in Cep OB4.
