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

Published version
Peer-reviewed

Type

Article

Change log

Authors

Belfiore, F 
Bundy, K 
Masters, K 
Bershady, M 

Abstract

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⊙)<10.5, while star-forming galaxies of higher mass show a significant decrease in sSFR in the central regions, a likely consequence of both larger bulges and an inside-out growth history. Our primary focus is the green valley, constituted by galaxies lying below the star formation main sequence, but not fully passive. In the green valley we find sSFR profiles that are suppressed with respect to star-forming galaxies of the same mass at all galactocentric distances out to 2 effective radii. The responsible quenching mechanism therefore appears to affect the entire galaxy, not simply an expanding central region. The majority of green valley galaxies of log(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 Σkpc (the mass surface density within 1 kpc), we show that a high Σkpc is not a sufficient condition for determining central quiescence.

Description

Keywords

galaxies: evolution, galaxies: fundamental parameters, galaxies: ISM

Journal Title

Monthly Notices of the Royal Astronomical Society

Conference Name

Journal ISSN

0035-8711
1365-2966

Volume Title

477

Publisher

Oxford University Press (OUP)

Rights

All rights reserved
Sponsorship
Science and Technology Facilities Council (ST/M001172/1)
European Research Council (695671)