  We investigate shock structures driven by merger events in high-resolution
simulations that result in a galaxy with a virial mass M ~ 1e12 Msol. We find
that the sizes and morphologies of the internal shocks resemble remarkably well
those of the newly-detected class of odd radio circles (ORCs). This would
highlight a so-far overlooked mechanism to form radio rings, shells and even
more complex structures around elliptical galaxies. Mach numbers of M = 2-3 for
such internal shocks are in agreement with the spectral indices of the observed
ORCs. We estimate that ~5 percent of galaxies could undergo merger events which
occasionally lead to such prominent structures within the galactic halo during
their lifetime, explaining the low number of observed ORCs. At the time when
the shock structures are matching the physical sizes of the observed ORCs, the
central galaxies are typically classified as early-type galaxies, with no
ongoing star formation, in agreement with observational findings. Although the
energy released by such mergers could potentially power the observed radio
luminosity already in Milky-Way-like halos, our predicted luminosity from a
simple, direct shock acceleration model is much smaller than the observed one.
Considering the estimated number of candidates from our cosmological
simulations and the higher observed energies, we suggest that the proposed
scenario is more likely for halo masses around 1e13 Msol in agreement with the
observed stellar masses of the galaxies at the center of ORCs. Such shocks
might be detectable with next generation X-ray instruments like the Line
Emission Mapper (LEM).
