  The PHENIX collaboration has measured low momentum direct photon radiation in
Au+Au collisions at 200 GeV, 62.4 GeV and 39 GeV, in Cu+Cu at 200 GeV as well
as in p+p, p+Au and d+Au at $\sqrt{s_{NN}} =$ 200 GeV. In these measurements
PHENIX has discovered a large excess over the scaled p+p yield of direct
photons in A+A collisions, and a non-zero excess, observed within systematic
uncertainties, over the scaled p+p yield in central p+A collisions. Another
finding is that at low-$p_{T}$ the integrated yield of direct photons,
$dN_{\gamma}/dy$, from large systems shows a behavior of universal scaling as a
function of the charged-particle multiplicity, $(dN_{ch}/d\eta)^{\alpha}$, with
$\alpha = 1.25$, which means that the photon production yield increases faster
than the charged-particle multiplicity.
