  Recent experimental results from RHIC and LHC on hard photon emission rates
in heavy-ion collisions indicate a large azimuthal asymmetry of photon emission
rate parameterized by the elliptic flow v_2. Motivated by a recent proposal
that the early magnetic field created by two colliding heavy-ions may be
responsible for this large azimuthal asymmetry of photon emission rate, we
compute the azimuthal dependence of the photon emission rate from a strongly
coupled finite temperature plasma with magnetic field in the framework of
gauge/gravity correspondence. We also propose and compute a new observable,
"in/out-plane polarization asymmetry", constructed from the polarization
dependence of the photon emission rates. We observe that both the azimuthal and
polarization asymmetry of photon emissions are strongly affected by the
triangle anomaly (chiral anomaly) for low frequency regime below 1 GeV.
