标题： 观测证据表明，核金属丰度和恒星形成率随着合并阶段而演化 显示英文标题

标题： Observational evidence for the evolution of nuclear metallicity and star formation rate as the merger stage

摘要： 我们研究了在合并序列中，通过其光学形态追踪的本地远红外选中的恒星形成星系的核气体相氧丰度和恒星形成率（SFR）的演化。 样本来自于IRAS点源目录红移巡天与1 Jy超亮红外星系样本和斯隆数字天空调查数据发布7数据库的交叉相关分析。 通过将我们的样本与在两个诊断中匹配归一化红移分布的对照样本进行比较来进行研究，这两个诊断分别是核气体相金属量与恒星质量的关系图和核SFR与恒星质量的关系图。 具有不同形态类型的星系表现出不同的质量-金属量关系（MZR）。 与对照样本定义的MZR相比，在给定恒星质量下，孤立螺旋星系的金属量与对照样本相当。 成对的螺旋星系和投影分离距离为$r_{p} >$20 kpc的相互作用星系表现出轻微的金属量稀释，为0.02-0.03 dex。 分离距离为$r_{p} <$20 kpc的相互作用星系、前合并体和高级合并体分别缺乏约0.06、0.05和0.04 dex的金属量。 这表明了一个演化趋势，即随着合并的进行，金属量逐渐降低，并且当两个星系紧密相互作用时，金属量最显著地被稀释。 随后，当星系合并时，星际介质（ISM）得到丰富。 这是首次观察到最终合并阶段的ISM丰富现象，这证明了超新星爆炸在影响核金属量方面的重要性。 同时，相对于对照样本的中心SFR增强与核气体相氧丰度同时演化。 我们的结果支持数值模拟的预测。 显示英文摘要

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 galaxies 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 (MZR). 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 $r_{p} >$ 20 kpc show mild metallicity dilution of 0.02-0.03 dex. Interacting galaxies with $r_{p} <$ 20 kpc, pre-mergers and advanced mergers are under-abundant 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 is observed, which demonstrates the importance of supernova explosion in affecting the nuclear metallicity. Meanwhile 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.