FROM OUTSIDE-IN TO INSIDE-OUT: GALAXY ASSEMBLY MODE DEPENDS ON STELLAR MASS

In this Letter, we investigate how galaxy mass assembly mode depends on stellar mass M-* using a large sample of similar to 10,000 low-redshift galaxies. Our galaxy sample is selected to have SDSS R-90 > 5 ''(), 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-* 10(10.5) M-circle dot galaxies have negative color gradients. When their central D(n)4000 index values exceed 1.6, the M-* 10(10.5) M-circle dot 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-* 10(10.5) M-circle dot. 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.