The Evolution of Advanced Merger (U)LIRGs on the Color-Stellar Mass Diagram

摘要

Based on a sample of 79 local advanced merger(adv-merger)(U)LIRGs, we search for evidence of quenching processes by investigating the distributions of star formation history indicators(EW(Hα),EW(Hδ_A) and D_n(4000)) on the NUV-r color-mass and SFR-M_* diagrams. The distributions of EW(Hα)and D_n(4000) on the NUV-r color-mass diagram show clear trends that at a given stellar mass, galaxies with redder NUV-r colors have smaller EW(Hα) and larger D_n(4000). The reddest adv-merger(U)LIRGs close to the green valley mostly have Dn(4000)> 1.4. In addition, in the SFR-M_* diagram, as the SFR decreases, the EW(Hα) decreases and the D_n(4000) increases, implying that the adv-merger(U)LIRGs on the star formation main sequence have more evolved stellar populations than those above the main sequence.These results indicate that a fraction of the adv-merger(U)LIRGs have already exhibited signs of fading from the starburst phase and that the NUV-r reddest adv-merger(U)LIRGs are likely at the initial stage of post-starbursts with an age of ~ 1 Gyr, which is consistent with the gas exhaustion time-scales. Therefore,our results offer additional support for the fast evolutionary track from the blue cloud to the red sequence.