Star-forming S0 Galaxies in SDSS-MaNGA: fading spirals or rejuvenated
  S0s?
  We investigate the origin of rare star-formation in an otherwise red-and-dead
population of S0 galaxies using spatially resolved spectroscopy. Our sample
consists of $120$ low redshift ($z<0.1$) star-forming S0 (SF-S0) galaxies from
the SDSS-IV MaNGA DR15. We have selected this sample after a visual inspection
of deep images from the DESI Legacy Imaging Surveys DR9 and the Subaru/HSC-SSP
survey PDR3, to remove contamination from spiral galaxies. We also construct
two control samples of star-forming spirals (SF-Sps) and quenched S0s (Q-S0s)
to explore their evolutionary link with the star-forming S0s. To study
star-formation at resolved scales, we use dust-corrected $H_\alpha$ luminosity
and stellar density ($\Sigma_\star$) maps to construct radial profiles of
star-formation rate (SFR) surface density ($\Sigma_{SFR}$) and specific SFR
(sSFR). Examining these radial profiles, we find that star-formation in SF-S0s
is centrally dominated as opposed to disc dominated star-formation in spirals.
We also compared various global (size-mass relation, bulge-to-total luminosity
ratio) and local (central stellar velocity dispersion) properties of SF-S0s to
those of the control sample galaxies. We find that SF-S0s are structurally
similar to the quenched S0s and are different from star-forming spirals. We
infer that SF-S0s are unlikely to be fading spirals. Inspecting stellar and gas
velocity maps, we find that more than $50\%$ of the SF-S0 sample shows signs of
recent galaxy interactions such as kinematic misalignment, counter-rotation,
and unsettled kinematics. Based on these results, we conclude that in our
sample of SF-S0s, star-formation has been rejuvenated, with minor mergers
likely to be a major driver.
