Constraining the thermally-pulsing asymptotic giant branch phase with
  resolved stellar populations in the Small Magellanic Cloud
  The thermally-pulsing asymptotic giant branch (TP-AGB) experienced by low-
and intermediate-mass stars is one of the most uncertain phases of stellar
evolution and the models need to be calibrated with the aid of observations. To
this purpose, we couple high-quality observations of resolved stars in the
Small Magellanic Cloud (SMC) with detailed stellar population synthesis
simulations computed with the TRILEGAL code. The strength of our approach
relies on the detailed spatially-resolved star formation history of the SMC,
derived from the deep near-infrared photometry of the VISTA survey of the
Magellanic Clouds, as well as on the capability to quickly and accurately
explore a wide variety of parameters and effects with the COLIBRI code for the
TP-AGB evolution. Adopting a well-characterized set of observations -- star
counts and luminosity functions -- we set up a calibration cycle along which we
iteratively change a few key parameters of the TP-AGB models until we
eventually reach a good fit to the observations. Our work leads to identify two
best-fitting models that mainly differ in the efficiencies of the third
dredge-up and mass loss in TP-AGB stars with initial masses larger than about 3
M$_{\odot}$. On the basis of these calibrated models we provide a full
characterization of the TP-AGB stellar population in the SMC in terms of
stellar parameters (initial masses, C/O ratios, carbon excess, mass-loss
rates). Extensive tables of isochrones including these improved models are
publicly available.
