Do blue compact galaxies have red halos?
  Red halos are faint, extended and extremely red structures that have been
reported around various types of galaxies since the mid-1990s. The colours of
these halos are too red to be reconciled with any hitherto known type of
stellar population, and instead indicative of a very bottom-heavy stellar
initial mass function (IMF). Due to the large mass-to-light ratios of such
stellar halos, they could contribute substantially to the baryonic masses of
galaxies while adding very little to their overall luminosities. The red halos
of galaxies therefore constitute potential reservoirs for some of the baryons
still missing from inventories in the low-redshift Universe. While most studies
of red halos have focused on disk galaxies, a red excess has also been reported
in the faint outskirts of blue compact galaxies (BCGs). A bottom-heavy IMF can
explain the colours of these structures as well, but due to model degeneracies,
stellar populations with standard IMFs and abnormally high metallicities have
also been demonstrated to fit the data. Here, we show that due to recent
developments in the field of spectral synthesis, the metallicities required in
this alternative scenario may be less extreme than previously thought. This
suggests that the red excess seen in the outskirts of BCGs may stem from a
normal, intermediate-metallicity host galaxy rather than a red halo of the type
seen around disk galaxies. The inferred host metallicity does, however, still
require the host to be more metal-rich than the gas in the central starburst of
BCGs, in contradiction with current simulations of how BCGs form.
