Variation of physical properties across the green valley for local galaxies

Abstract

We selected a sample of nearby galaxies from the Sloan Digital Sky Survey Data Release 7 (SDSS DR7) to investigate the variation of physical properties from the blue cloud to green valley to red sequence. The sample is limited to a narrow range in the color-stellar mass diagram. After splitting green valley galaxies into two parts—a bluer green valley (green 1) and a redder one (green 2) and three stellar mass bins, we investigate the variation of physical properties across the green valley region. Our main results are as follows: (i) The percentages of pure bulge and bulge-dominated/elliptical galaxies increase gradually from blue cloud to red sequence while the percentages of pure disk and disk-dominated/spiral galaxies decrease gradually in all stellar mass bins and different environments. (ii) With the analysis of morphological and structural parameters (e.g., concentration (C) and the stellar mass surface density within the central 1 kpc (Σ1)), red galaxies show more luminous and compact cores than both green valley and blue galaxies, while blue galaxies show the opposite behavior in all stellar mass bins. (iii) A strong negative (positive) relationship between bulge-to-total light ratio (B/T) and specific star formation rate (sSFR) (D4000) is found from blue to red galaxies. Our results indicate that the growth in bulge plays an important role when the galaxies change from the blue cloud, to the green valley and to the red sequence.