Complex central structures suggest complex evolutionary paths for barred S0 galaxies

We investigate three barred lenticular galaxies (NGC 2681, NGC 3945 and NGC 4371), which were previously reported to have complex central structures but without a detailed structural analysis of these galaxies' high-resolution data. We have therefore performed fourto six-component (pseudo-) bulge/disc/bar/ring/point source) decompositions of the composite (Hubble Space Telescope plus ground-based) surface brightness profiles. We find that NGC 2681 hosts three bars, while NGC 3945 and NGC 4371 are double-and single-barred galaxies, respectively, in agreement with past isophotal analysis. We find that the bulges in these galaxies are compact, and have Sersic indices of n similar to 2.2-3.6 and stellar masses of M-* similar to 0.28 x 10(10)-1.1 x 10(10) M-circle dot. NGC 3945 and NGC 4371 have intermediate-scale 'pseudo-bulges' that are well described by a Sersic model with low n less than or similar to 0.5 instead of an exponential (n = 1) profile as done in the past. We measure emission line fluxes enclosed within nine different elliptical apertures, finding that NGC 2681 has a low-ionization nuclear emission region (LINER)-type emission inside R similar to 3 arcsec, but the emission line due to star formation is significant when aperture size is increased. In contrast, NGC 3945 and NGC 4371 have composite (active galactic nucleus plus star-forming)-and LINER-type emissions inside and outside R similar to 2 arcsec, respectively. Our findings suggest that the three galaxies have experienced a complex evolutionary path. The bulges appear to be consequences of an earlier violent merging event while subsequent disc formation via gas accretion and bar-driven perturbations may account for the build-up of pseudo-bulges, bars, rings and point sources.