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 Σ 1 kpc (the mass surface density within 1 kpc), we show that a high Σ 1 kpc is not a sufficient condition for determining central quiescence.