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

Abstract

Using a sample of ∼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 Sérsic 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 , supporting  NUV– r as a good photometric indicator of stellar age (or specific star formation rate). First, we find that at 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 . Second, the central NUV– r shows no dependence on Sérsic index n at , 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 exhibit similar star formation activity from the inner region to the region. In contrast, a considerable fraction of the galaxies, especially those with a high n , have harbored a relatively inactive bulge component.