Star formation rate density, $Sigma_{rm SFR}$, has shown a remarkable correlation with both components of the baryonic mass at kpc scales (i.e., the stellar mass density, and the molecular gas mass density; $Sigma_{ast}$, and $Sigma_{rm mol}$, respectively) for galaxies in the nearby Universe. In this study we propose an empirical relation between $Sigma_{rm SFR}$ and the baryonic mass surface density ($Sigma_{rm b}$ =$Sigma_{rm mol,Av}$ + $Sigma_{ast}$; where $Sigma_{rm mol,Av}$ is the molecular gas density derived from the optical extinction, Av) at kpc scales using the spatially-resolved properties of the MaNGA survey - the largest sample of galaxies observed via Integral Field Spectroscopy (IFS, $sim$ 8400 objects). We find that $Sigma_{rm SFR}$ tightly correlates with $Sigma_{rm b}$. Furthermore, we derive an empirical relation between the $Sigma_{rm SFR}$ and a second degree polynomial of $Sigma_{rm b}$ yielding a one-to-one relation between these two observables. Both, $Sigma_{rm b}$ and its polynomial form show a stronger correlation and smaller scatter with respect to $Sigma_{rm SFR}$ than the relations derived using the individual components of $Sigma_{rm b}$. Our results suggest that indeed these three parameters are physically correlated, suggesting a scenario in which the two components of the baryonic mass regulate the star-formation activity at kpc scales.
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