Centrality dependence of low-momentum direct-photon production in Au$+$Au collisions at $sqrt{s_{_{NN}}}=200$ GeV

The PHENIX experiment at RHIC has measured the centrality dependence of the direct photon yield from Au$+$Au collisions at $sqrt{s_{_{NN}}}=200$ GeV down to $p_T=0.4$ GeV/$c$. Photons are detected via photon