QUENCHING DEPENDS ON MORPHOLOGIES: IMPLICATIONS FROM THE ULTRAVIOLET-OPTICAL RADIAL COLOR DISTRIBUTIONS IN GREEN VALLEY GALAXIES

Zhizheng Pan, Jinrong Li, Weipeng Lin, Jing Wang, Xu Kong
2014 Astrophysical Journal Letters  
In this Letter, we analyse the radial UV-optical color distributions in a sample of low redshift green valley (GV) galaxies, with the Galaxy Evolution Explorer (GALEX)+Sloan Digital Sky Survey (SDSS) images, to investigate how the residual recent star formation distribute in these galaxies. We find that the dust-corrected u-r colors of early-type galaxies (ETGs) are flat out to R_90, while the colors turn blue monotonously when r>0.5R_50 for late-type galaxies (LTGs). More than a half of the
more » ... s are blue-cored and have remarkable positive NUV-r color gradients, suggesting that their star formation are centrally concentrated; the rest have flat color distributions out to R_90. The centrally concentrated star formation activity in a large portion of ETGs is confirmed by the SDSS spectroscopy, showing that ∼50 ETGs have EW(Hα)>6.0 Å. For the LTGs, 95 radial color profiles, which can be interpreted as a red bulge plus an extended blue disk. The links between the two kinds of ETGs, e.g., those objects having remarkable "blue-cored" and those having flat color gradients, are less known and require future investigations. It is suggested that the LTGs follow a general picture that quenching first occur in the core regions, and then finally extend to the rest of the galaxy. Our results can be re-examined and have important implications for the IFU surveys, such as MaNGA and SAMI.
doi:10.1088/2041-8205/792/1/l4 fatcat:574trzmxqzgjfbympzwfrbsjey