  Intergalactic magnetic fields in the voids of the large-scale structure can
be probed via measurements of secondary gamma-ray emission from gamma-ray
interactions with extragalactic background light. Lower bounds on the magnetic
field in the voids were derived from the non-detection of this emission. It is
not clear a priori what kind of magnetic field is responsible for the
suppression of the secondary gamma-ray flux: a cosmological magnetic field that
might be filling the voids or the field spread by galactic winds driven by star
formation and active galactic nuclei. We used IllustrisTNG cosmological
simulations to study the effect of magnetized galactic wind bubbles on the
secondary gamma-ray flux. We show that within the IllustrisTNG model of
baryonic feedback, the galactic wind bubbles typically provide
energy-independent secondary flux suppression at the level of about 10%. The
observed flux suppression effect has to be due to the cosmological magnetic
field in the voids. This might not be the case for a special case when the
primary gamma-ray source has a hard intrinsic gamma-ray spectrum that peaks in
the energy range above 50 TeV. In this case, the observational data may be
strongly affected by the magnetized bubble that is blown by the source host
galaxy.
