标题： H II星系发射线序列的建模 显示英文标题

标题： Modeling the emission line sequence of H II galaxies

摘要： 利用一个前所未有的样本（约400个天体）的电离氢区星系，其中氧丰度是通过 [OIII] 4363/5007 线比所推导的温度获得的，我们确认电离氢区星系在许多与线比和Hβ当量宽度相关的图中形成一条非常窄的序列。 我们将样本分为三个金属丰度区间，每个区间都与对应金属丰度的演化星暴光致电离模型序列进行比较。 我们的目标是找出在什么条件下理论序列可以再现所有观测到的趋势。 考虑到存在一个较老的非电离恒星群体（已有独立证据表明这一点），如果考虑视场修正，并假设覆盖因子以指数方式随时间衰减，衰减时间尺度为3百万年，则简单的大气泡绝热膨胀模型能很好地再现观测图。 我们发现He II 4686 谱线发射过于频繁且出现在太宽范围的Hβ当量宽度内，无法归因于沃尔夫-拉叶星的硬辐射场或最新一代恒星产生的X射线。 假设He II 4686谱线是由温度为10^6 K的热等离子体光致电离引起的，那么至少有一半的源需要总X射线亮度为10^40 - 4x10^40 erg/s。 我们发现了在几百万年的时标上氮元素自富集的证据，并认为氧元素也可能发生自富集。 显示英文摘要

摘要： Using a sample of unprecedented size (about 400 objects) of H II galaxies in which the oxygen abundances have been obtained using the temperature derived from the [OIII] 4363/5007 line ratio, we confirm that the H II galaxies form a very narrow sequence in many diagrams relating line ratios and Hbeta equivalent width. We divide our sample in three metallicity bins, each of which is compared with sequences of photoionization models for evolving starbursts with corresponding metallicity. Our aim is to find under what conditions a theoretical sequence can reproduce all the observed trends. Taking into account the presence of an older, non-ionizing stellar population, for which independent indications exist, we find that the simple model of an adiabatic expanding bubble reproduces the observational diagrams very well if account is taken of an aperture correction and the covering factor is assumed to decrease with time exponentially with an e-folding time of 3 Myr. We find that the He II 4686 nebular line emission occurs too frequently and in too wide a range of EW(Hbeta) to be attributable to either the hard radiation field from Wolf-Rayet stars or the X-rays produced by the latest stellar generation. Assuming that the He II 4686 line is due to photoionization by a hot plasma at a temperature of 10^6 K, a total X-ray luminosity of 10^40 - 4x10^40 erg/s is required for at least half of the sources. We find evidence for self-enrichment in nitrogen on a time scale of several Myr, and argue for a possible self-enrichment in oxygen as well.