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(HδA) and Dn(4000)) on the NUV-r color-mass and SFR-M* diagrams.The distributions of EW(Hα)and Dn(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 Dn (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 Dn (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.