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

doi:10.1088/2041-8205/792/1/L4

paper

Quenching depends on morphologies: implications from the ultraviolet-optical radial color distributions in Green Valley Galaxies

arXiv:1407.6715 · doi:10.1088/2041-8205/792/1/L4

Abstract

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 $r > 0.5 R_{50}$ for late-type galaxies (LTGs). More than a half of the ETGs 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 $\sim$ 50 % ETGs have EW(H $α$ ) $> 6.0$ Å. For the LTGs, 95% of them show uniform 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.

ApJ Letter, accepted. Five figures

Quenching depends on morphologies: implications from the ultraviolet-optical radial color distributions in Green Valley Galaxies

Abstract

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