SDSS IV MaNGA - sSFR profiles and the slow quenching of discs in green valley galaxies

We study radial profiles in Hα equivalent width and specific star formation rate (sSFR) derived from spatially-resolved SDSS-IV MaNGA spectroscopy to gain insight on the physical mechanisms that suppress star formation and determine a galaxy’s location in the SFR- M⋆ diagram. Even within the star-forming ‘main sequence’, the measured sSFR decreases with stellar mass, both in an integrated and spatially-resolved sense. Flat sSFR radial profiles are observed for log(M⋆/M⊙)⋆/M⊙)>10.0 are classified spectroscopically as central low-ionisation emission-line regions (cLIERs). Despite displaying a higher central stellar mass concentration, the sSFR suppression observed in cLIER galaxies is not simply due to the larger mass of the bulge. Drawing a comparison sample of star forming galaxies with the same M⋆ and Σ1 kpc (the mass surface density within 1 kpc), we show that a high Σ1 kpc is not a sufficient condition for determining central quiescence