  Nearby galaxies are the end result of their cosmological evolution, which is
predicted to be influenced by the growth of their host dark matter halos. This
co-evolution potentially leaves signatures in present-day observed galaxy
properties, which might be essential to further understand how the growth and
properties of galaxies are connected to those of their host halos. In this
work, we study the evolutionary histories of nearby galaxies both in terms of
their host halos and the scatter of the star-forming main sequence by
investigating their time-resolved stellar populations using absorption optical
spectra drawn from the Sloan Digital Sky Survey. We find that galaxy star
formation histories depend on the masses of their host halos, and hence they
shape the evolution of the star-forming main sequence over cosmic time.
Additionally, we also find that the scatter around the z=0 star-forming main
sequence is not (entirely) stochastic, as galaxies with currently different
star formation rates have experienced, on average, different star formation
histories. Our findings suggest that dark matter halos might play a key role in
modulating the evolution of star formation in galaxies, and thus of the main
sequence, and further demonstrate that galaxies at different evolutionary
stages contribute to the observed scatter of this relation.
