  We compute the spectra and elliptic flow of thermal photons emitted in
ultrarelativistic heavy-ion collisions (URHICs) at RHIC and LHC. The thermal
emission rates are taken from complete leading-order rates for the QGP and
hadronic many-body calculations including baryons and antibaryons, as well as
meson-exchange reactions (including Bremsstrahlung). We first update previous
thermal fireball calculations by implementing a lattice-QCD based equation of
state and extend them to compare to recent LHC data. We then scrutinize the
space-time evolution of Au-Au collisions at RHIC by employing an ideal
hydrodynamic model constrained by bulk- and multistrange-hadron spectra and
elliptic flow, including a non-vanishing initial flow. We systematically
compare the evolutions of temperature, radial flow, azimuthal anisotropy and
four-volume, and exhibit the temperature profile of thermal photon radiation.
Based on these insights, we put forward a scenario with a "pseudo-critical
enhancement" of thermal emission rates, and investigate its impact on RHIC and
LHC direct photon data.
