From outside-in to inside-out: galaxy assembly mode depends on stellar mass.
PAN Z., LI J., LIN W., WANG J., FAN L. and KONG X.
Abstract (from CDS):
In this Letter, we investigate how galaxy mass assembly mode depends on stellar mass M* using a large sample of ∼10,000 low-redshift galaxies. Our galaxy sample is selected to have SDSS R90 > 5°.0, which allows the measures of both the integrated and the central NUV-r color indices. We find that in the M*-(NUV-r) green valley (GV), the M* < 1010M☉ galaxies mostly have positive or flat color gradients, while most of the M* > 1010.5 M☉ galaxies have negative color gradients. When their central Dn4000 index values exceed 1.6, the M* < 1010.0 M☉ galaxies have moved to the UV red sequence, whereas a large fraction of the M* > 1010.5 M☉ galaxies still lie on the UV blue cloud or the GV region. We conclude that the main galaxy assembly mode is transiting from ''the outside-in'' mode to ''the inside-out'' mode at M* < 1010.0 M☉ and at M* > 1010.5 M☉. We argue that the physical origin of this is the compromise between the internal and the external processes that drive the star formation quenching in galaxies. These results can be checked with the upcoming large data produced by the ongoing integral field spectroscopic survey projects, such as CALIFA, MaNGA, and SAMI in the near future.
galaxies: evolution - galaxies: star formation