Spatially-resolved NUV-r color of local star-forming galaxies and clues for quenching

TL;DR

This study investigates how the spatial distribution of NUV-r color in local star-forming galaxies relates to galaxy structure and quenching, revealing mass-dependent differences in star formation activity and bulge development.

Contribution

It provides the first detailed analysis of spatially-resolved NUV-r colors in relation to galaxy mass and structure, linking color gradients to quenching processes.

Findings

Central NUV-r becomes redder than outer regions in massive galaxies.

No dependence of central NUV-r on Sersic index at lower masses.

Massive, high-n galaxies show evidence of inactive bulges.

Abstract

Using a sample of ~6,000 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 S\'{e}rsic index n in order 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 Dn4000, supporting that NUV-r is a good photometric indicator of stellar age (or specific star formation rate). We find that: (1) At M*<10^{10.2}M_{\sun}, 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_{\sun}. (2) The central NUV-r shows no dependence on S\'{e}rsic index n at M*<10^{10.2}M_{\sun}, 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*<10^{10.2}M_{\sun} 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*>10^{10.2}M_{\sun} galaxies, especially those with a high n, have harbored a relatively inactive bulge component.