  Post-Starburst Quasars (PSQs) are hypothesized to represent a stage in the
evolution of massive galaxies in which the star formation has been recently
quenched due to the feedback of the nuclear activity. In this paper our goal is
to test this scenario with a resolved stellar population study of the PSQ
J0210-0903, as well as of its emitting gas kinematics and excitation. We have
used optical Integral Field Spectroscopy obtained with the Gemini GMOS
instrument at a velocity resolution of ~120 km/s and spatial resolution of ~0.5
kpc. We find that old stars dominate the luminosity (at 4700 \AA) in the inner
0.3 kpc (radius), while beyond this region (at ~0.8 kpc) the stellar population
is dominated by both intermediate age and young ionizing stars. The gas
emission-line ratios are typical of Seyfert nuclei in the inner 0.3 kpc, where
an outflow is observed. Beyond this region the line ratios are typical of
LINERs and may result from the combination of diluted radiation from the
nucleus and ionization from young stars. The gas kinematics show a combination
of rotation in the plane of the galaxy and outflows, observed with a maximum
blueshift of -670 km/s. We have estimated a mass outflow rate in ionized gas in
the range 0.3--1.1 M_sun/yr and a kinetic power for the outflow of dE/dt ~
1.4--5.0 x 10^40 erg/s ~0.03% - 0.1% x L_bol. This outflow rate is two orders
of magnitude higher than the nuclear accretion rate of ~8.7 x 10^-3 M_sun/yr,
thus being the result of mass loading of the nuclear outflow by circumnuclear
galactic gas. Our observations support an evolutionary scenario in which the
feeding of gas to the nuclear region has triggered a circumnuclear starburst
100's Myr ago, followed by the triggering of the nuclear activity, producing
the observed gas outflow which may have quenched further star formation in the
inner 0.3 kpc.
