THE SPATIALLY RESOLVED NUV-r COLOR OF LOCAL STAR-FORMING GALAXIES AND CLUES FOR QUENCHING

Using a sample of similar to 6000 local face-on star-forming galaxies (SFGs) we examine the correlations between the NUV-r colors both inside and outside the half-light radius, stellar mass M-*, and Sersic index n to understand how the quenching of star formation is linked to galaxy structure. For these less dust-attenuated galaxies, NUV-r is found to be linearly correlated with D-n 4000, supporting NUV-r as a good photometric indicator of stellar age (or specific star formation rate). First, we find that at M-* < 10(10.2)M(circle dot) the central NUV-r is on average only 0.25 mag redder than the outer NUV-r; the intrinsic value would be even smaller after accounting for dust correction. However, the central NUV-r becomes systematically much redder than the outer NUV-r for more massive galaxies at M* > 10(10.2)M(circle dot). Second, the central NUV-r shows no dependence on Sersic index n at M* < 10(10.2)M(circle dot), while above this mass galaxies with a higher n tend to be redder in the central NUV-r color. These results suggest that galaxies with M* < 101 2M(circle dot) exhibit similar star formation activity from the inner R < R-50 region to the R > R-50 region. In contrast, a considerable fraction of the M* > 101(0.2)M(circle dot) galaxies, especially those with a high n, have harbored a relatively inactive bulge component.