标题： 星系缩小和氧与氮丰度的红移演化：N/H-O/H图中的散射起源 显示英文标题

标题： Galaxy downsizing and the redshift evolution of oxygen and nitrogen abundances: origin of the scatter in the N/H-O/H diagram

摘要： 发射线星系的氧和氮丰度随红移的变化在斯隆数字巡天中被考虑，针对四个不同恒星质量范围的星系，从10^11.3 M_sun到10^10.2 M_sun。 我们测量了它们的谱线流量，并使用最近的标定方法推导出O和N的丰度。 O和N丰度随红移的变化明显显示出星系缩小效应，其中高质量星系在较早时期停止了富集（以及恒星形成），并在较晚时期转移到低质量星系。 对N/H - O/H图中的散射来源进行了研究。 最高质量的星系，其中O和N的富集以及恒星形成已经停止，在N/H -- O/H图中占据一个狭窄的区域，定义了一个上限。 当前仍在进行恒星形成的低质量星系则向下移动，趋向于N/H - O/H图中较低的N/H值。 这种向下移动是由于N和O富集之间的时间延迟造成的。 这种时间延迟以及星系中不同的恒星形成历史导致了N/H -- O/H图中的较大散射。 显示英文摘要

摘要： The oxygen and nitrogen abundance evolutions with redshift of emission-line galaxies in the Sloan Digital Sky Survey are considered for four intervals of galaxy stellar masses, ranging from 10^11.3 M_sun to 10^10.2 M_sun. We have measured their line fluxes and derived the O and N abundances using recent calibrations. The evolution of O and N abundances with redshift clearly shows the galaxy downsizing effect, where enrichment (and hence star formation) ceases in high-mass galaxies at earlier times and shifts to lower-mass galaxies at later epochs. The origin of the scatter in the N/H - O/H diagram has been examined. The most massive galaxies, where O and N enrichment and star formation has already stopped, occupy a narrow band in the N/H -- O/H diagram, defining an upper envelope. The less massive galaxies which are still undergoing star formation at the current epoch are shifted downwards, towards lower N/H values in the N/H - O/H diagram. This downward shift is caused by the time delay between N and O enrichment. This time delay together with the different star formation histories in galaxies is responsible for the large scatter in the N/H -- O/H diagram.