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Three basic ingredients are required to generate a simple stellar population(SSP) library, i.e., an initial mass function (IMF), a stellar evolutionmodel/isochrones, and an empirical/theoretical stellar spectral library.However, there are still some uncertainties to the determination andunderstanding of these ingredients. We perform the spectral fitting to test therelative parameter offsets between these uncertainties using two differentstellar population models, two different empirical stellar libraries, twodifferent isochrones, and the Salpeter and Chabrier IMFs. Based on thesesetups, we select five SSP libraries generated with the Galaxev/STELIB andVazdekis/MILES models, and apply them to the pPXF full-spectrum fitting of bothMaNGA and mock spectra. We find that: 1) Compared to the Galaxev/STELIB model,spectral fitting qualities with the Vazdekis/MILES model have significantimprovements for those metal-rich (especially over-solar) spectra, which causebetter reduced $\chi^2$ distributions and more precisely fitted absorptionlines. This might due to the lack of metal rich stars in the empirical STELIBlibrary, or code improvement of the Vazdekis model. 2) When applying theVazdekis/MILES model for spectral fitting, the IMF variation will lead to notonly a systematic offset in $M_*/L_r$, but also offsets in age and metallicity,and these offsets increase with increasing stellar population ages. However,the IMF-variation caused metallicity offsets disappear in the case ofGalaxev/STELIB based libraries. 3) The Padova2000 model provides a better matchto the MaNGA galaxy spectra at [M/H]$_L<-1.0$, while the BaSTI model match thelocal galaxy spectra better at [M/H]$_L>-1.0$. Current tests suggest thatspectral fitting with the Vazdekis/MILES+BaSTI combination would be a betterchoice for local galaxies.

Recovering stellar population parameters via different population models and stellar libraries