Star-formation in CALIFA early-type galaxies. A matter of discs
  The star formation main sequence (SFMS) is a tight relation between the
galaxy star formation rate (SFR) and its total stellar mass ($M_\star$).
Early-type galaxies (ETGs) are often considered as low-SFR outliers of this
relation. We study, for the first time, the separated distribution in the SFR
vs. $M_\star$ of bulges and discs of 49 ETGs from the CALIFA survey. This is
achieved using C2D, a new code to perform spectro-photometric decompositions of
integral field spectroscopy datacubes. Our results reflect that: i) star
formation always occurs in the disc component and not in bulges; ii)
star-forming discs in our ETGs are compatible with the SFMS defined by star
forming galaxies at $z \sim 0$; iii) the star formation is not confined to the
outskirts of discs, but it is present at all radii (even where the bulge
dominates the light); iv) for a given mass, bulges exhibit lower sSFR than
discs at all radii; and v) we do not find a deficit of molecular gas in bulges
with respect to discs for a given mass in our ETGs. We speculate our results
favour a morphological quenching scenario for ETGs.
