  Recent classical-statistical numerical simulations have established the
"bottom-up" thermalization scenario of Baier et al. as the correct weak
coupling effective theory for thermalization in ultrarelativistic heavy-ion
collisions. We perform a parametric study of photon production in the various
stages of this bottom-up framework to ascertain the relative contribution of
the off-equilibrium "Glasma" relative to that of a thermalized Quark-Gluon
Plasma. Taking into account the constraints imposed by the measured charged
hadron multiplicities at RHIC and the LHC, we find that Glasma contributions
are important especially for large values of the saturation scale at both
energies. These non-equilibrium effects should therefore be taken into account
in studies where weak coupling methods are employed to compute photon yields.
