Probing the star formation origin of gamma rays from 3FHL J1907.0+0713
  Star-forming (SF) regions embedded inside giant molecular clouds (GMCs) are
potential contributors to Galactic gamma rays. The gamma-ray source 3FHL
J1907.0+0713 is detected with a significance of roughly 13$\sigma$ in the 0.2
$-$ 300 GeV energy range after the removal of gamma-ray pulsation periods of
PSR J1906+0722 from the Fermi-LAT data set of about 10 years. The energy
spectrum of 3FHL J1907.0+0713 is best-fitted to a power law model with a
spectral index of 2.26 $\pm$ 0.05. The CO($J$ = 1$-$0) data taken by NANTEN2
revealed that 3FHL J1907.0+0713 is overlapping with a GMC having a peak
velocity of about 38 km s$^{-1}$. The best-fitting location of 3FHL
J1907.0+0713 is measured to be approximately 0.13 degrees away from the
Galactic supernova remnant (SNR) 3C 397 and it overlaps with a star that is
associated with a bow-shock nebula. We show that there is no physical
connection between 3FHL J1907.0+0713, 3C 397, as well as any positional
coincidence with the pulsar. The spectrum of 3FHL J1907.0+0713 is fitting to
both hadronic and leptonic gamma-ray emission models and the total luminosity
at a distance of 2.6 kpc is calculated to be 1.1 $\times$ 10$^{34}$ erg
s$^{-1}$. We also discuss possible SF origins of gamma rays from 3FHL
J1907.0+0713, where SNRs, massive protostar outflows, stellar winds from
runaway stars, colliding wind binaries, and young stellar clusters are
considered as candidate sources.
