  High energy radiation from nonthermal particles accelerated in relativistic
magnetic reconnection is thought to be important in many astrophysical systems,
ranging from blazar jets and black hole accretion disk coronae to pulsars and
magnetar flares. The presence of a substantial density of high energy photons
($>$MeV) in these systems can make two-photon pair production ($\gamma\gamma\to
e^-e^+$) an additional source of plasma particles and can affect the radiative
properties of these objects. We present the results of novel particle-in-cell
simulations that track both the radiated synchrotron photons and the created
pairs, with which we study the evolution of a two-dimensional reconnecting
current sheet in pair plasma. Synchrotron radiation from accelerated particles
in the current sheet produces hot secondary pairs in the upstream which are
later advected into the current sheet where they are reaccelerated and produce
more photons. In the optically thin regime, when most of the radiation is
leaving the upstream unaffected, this process is self-regulating and depends
only on the background magnetic field and the optical depth of photons to pair
production. The extra plasma loading also affects the properties of
reconnection. We study how the inflow of the secondary plasma, with
multiplicities up to several hundred, reduces the effective magnetization of
the plasma, suppressing the acceleration and thus decreasing the high energy
photon spectrum cutoff. This offers an explanation for the weak dependence of
the observed gamma-ray cutoff in pulsars on the magnetic field at the light
cylinder.
