Observational evidence for the evolution of nuclear metallicity and star formation rate with the merger stage  

作　　者：Rui Guo Cai-Na Hao Xiao-Yang Xia Peng Wei Xin Guo 

机构地区：[1]National Astronomical,Observatories,Chinese Academy of Sciences,Beijing 100012,China [2]University of Chinese Academy of Sciences,Beijing 100049,China [3]Tianjin Astrophysics Center,Tianjin Normal University,Tianjin 300387,China [4]School of Astronomy and Space Science,Nanjing University,Nanjing 210093,China

出　　处：《Research in Astronomy and Astrophysics》2016年第7期113-124,共12页天文和天体物理学研究（英文版）

基　　金：supported by the National Natural Science Foundation of China(Grant Nos.11373027 and11003015);SRF for ROCS,SEM.Funding for the creation and distribution of the SDSS Archive has been provided by the Alfred P.Sloan Foundation,the Participating Institutions,the National Aeronautics and Space Administration,the National Science Foundation,the U.S.Department of Energy,the Japanese Monbukagakusho,and the Max Planck Society

摘　　要：We investigate the evolution of nuclear gas-phase oxygen abundance and star formation rate（SFR） of local far-infrared selected star-forming galaxies along the merger sequence, as traced by their optical morphologies. The sample was drawn from a cross-correlation analysis of the IRAS Point Source Catalog Redshift Survey and 1 Jy ultraluminous infrared galaxy sample with the Sloan Digital Sky Survey Data Release 7 database. The investigation is done by comparing our sample to a control sample matched in the normalized redshift distribution in two diagnostics, which are the nuclear gas-phase metallicity vs.stellar mass and the nuclear SFR vs. stellar mass diagrams. Galaxies with different morphological types show different mass-metallicity relations（MZRs）. Compared to the MZR defined by the control sample,isolated spirals have comparable metallicities with the control sample at a given stellar mass. Spirals in pairs and interacting galaxies with projected separations of rp 〉 20 kpc show a mild metallicity dilution of0.02–0.03 dex. Interacting galaxies with rp 〈 20 kpc, pre-mergers and advanced mergers are underabundant by～0.06,～0.05 and～0.04 dex, respectively. This shows an evolutionary trend that the metallicity is increasingly depressed as the merging proceeds and it is diluted most dramatically when two galaxies are closely interacting. Afterwards, the interstellar medium（ISM） is enriched when the galaxies coalesce.This is the first time that such ISM enrichment at the final coalescence stage has been observed, which demonstrates the importance of supernova explosions in affecting the nuclear metallicity. Moreover, the central SFR enhancement relative to the control sample evolves simultaneously with the nuclear gas-phase oxygen abundance. Our results support the predictions from numerical simulations.We investigate the evolution of nuclear gas-phase oxygen abundance and star formation rate（SFR） of local far-infrared selected star-forming galaxies along the merger sequence, as traced by their optical morphologies. The sample was drawn from a cross-correlation analysis of the IRAS Point Source Catalog Redshift Survey and 1 Jy ultraluminous infrared galaxy sample with the Sloan Digital Sky Survey Data Release 7 database. The investigation is done by comparing our sample to a control sample matched in the normalized redshift distribution in two diagnostics, which are the nuclear gas-phase metallicity vs.stellar mass and the nuclear SFR vs. stellar mass diagrams. Galaxies with different morphological types show different mass-metallicity relations（MZRs）. Compared to the MZR defined by the control sample,isolated spirals have comparable metallicities with the control sample at a given stellar mass. Spirals in pairs and interacting galaxies with projected separations of rp 〉 20 kpc show a mild metallicity dilution of0.02–0.03 dex. Interacting galaxies with rp 〈 20 kpc, pre-mergers and advanced mergers are underabundant by～0.06,～0.05 and～0.04 dex, respectively. This shows an evolutionary trend that the metallicity is increasingly depressed as the merging proceeds and it is diluted most dramatically when two galaxies are closely interacting. Afterwards, the interstellar medium（ISM） is enriched when the galaxies coalesce.This is the first time that such ISM enrichment at the final coalescence stage has been observed, which demonstrates the importance of supernova explosions in affecting the nuclear metallicity. Moreover, the central SFR enhancement relative to the control sample evolves simultaneously with the nuclear gas-phase oxygen abundance. Our results support the predictions from numerical simulations.

关 键 词：GALAXIES abundances galaxies evolution galaxies interactions galaxies starburst galaxies star formation infrared GALAXIES 

分 类 号：P152[天文地球—天文学]