  The observed radial accelerations of 462 Early-type galaxies (ETGs) at their
half-mass radii are discussed. They are compared to the baryonic masses of the
same galaxies, which are derived from theoretical expectations for their
stellar populations and cover a range from $\approx 10^4 \, {\rm M}_{\odot}$ to
$\approx 10^{11} \, {\rm M}_{\odot}$. Both quantities are plotted against each
other, and it is tested whether they lie (within errors) along theoretical
radial acceleration relations (RARs). We choose the Newtonian RAR and two
Milgromian, or MONDian RARs. At low radial accelerations (corresponding to low
masses), the Newtonian RAR fails without non-baryonic dark matter, but the two
MONDian ones may work, provided moderate out-of-equilibrium dynamics in some of
the low-mass ETGs. However all three RARs fail at high accelerations
(corresponding to high masses) if all ETGs have formed their stellar
populations with the canonical stellar initial mass function (IMF). A much
better agreement with the observations can however be accomplished, if the
theory of the integrated galaxy-wide stellar initial mass functions (IGIMFs) is
used instead. This is because the IGIMF-theory predicts the formation of an
overabundance of stellar remnants during the lifetime of the massive ETGs. Thus
their baryonic masses today are higher than they would be if the ETGs had
formed with a canonical IMF. Also the masses of the stellar-mass black holes
should be rather high, which would mean that most of them probably formed when
the massive ETGs were not as metal-enriched as they are today. The
IGIMF-approach confirms downsizing.
