Stellar Mass Census of $S^4G$ Local Bars

Abstract: Bars are stellar structures commonly found in disk galaxies and important agents of secular evolution. Quantifying the stellar mass content of bars provides a physically motivated approach to assess how bar growth depends on galaxy mass and internal structure. We perform a GALFITM multi-band mid-infrared two-dimensional decomposition of 344 barred galaxies from the Spitzer Survey of Stellar Structure in Galaxies ($S<sup>4G$) in the 3.6 and 4.5 $μ$m bands. We estimate the stellar mass associated with each structural component (i.e., disk, bulge, bar, and nuclear point source) and investigate how bar properties correlate with global galaxy characteristics. Our final models consist of 2-4 components per galaxy, with the simplest configuration (disk + bar) typically associated with low-mass systems. We find that more massive galaxies with prominent bulges host more massive bars and higher median bar-to-total stellar mass ratios. These bulges generally present Sérsic indices below 2, consistent with a photometric signature of nuclear stellar disks. Additionally, when we consider the relative bar lengths at a fixed galaxy mass, we find a bimodal distribution where galaxies with bulges host relatively longer bars compared to their bulgeless counterparts. These findings could be the result of different evolutionary paths, possibly linked to different disk formation epochs, allowing bars more time to grow in size and mass. Our study indicates that bar evolution may follow distinct pathways across different galaxy mass regimes, and is likely influenced by secular processes and environmental effects.