  Stellar population studies of massive early-type galaxies (ETGs) suggest that
the stellar initial mass function may not be universal. In particular, the
centres of ETGs seem to contain an excess of low-mass dwarf stars compared to
our own Galaxy. Through high resolution MUSE IFU data, we carry out a detailed
study of the stellar populations of eight massive ETGs. We use full spectrum
fitting to determine ages, element abundances, and IMF slopes for spatially
binned spectra. We measure flat gradients in age and [Mg/Fe] ratio, as well as
negative gradients in metallicity and [Na/Fe]. We detect IMF gradients in some
galaxies, with the centres hosting bottom-heavy IMFs and mass excess factors
between 1.5-2.5 compared to a Kroupa IMF. The IMF slope below 0.5~M$_\odot$
varies for our galaxy sample between 1-2.8, with negative radial gradients,
while the IMF slope between 0.5-1~M$_\odot$ has a steep value of $\sim$3 with
mildly positive gradients for most galaxies. For M87, we find excellent
agreement with the dynamical M/L as a function of radius. For the other
galaxies, we find systematically higher M/L from stellar populations compared
to orbit-based dynamical analysis of the same data. This discrepancy increases
with NaI strength, suggesting a combination of calibration issues of this line
and correlated uncertainties.
