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外文期刊>The Astrophysical journal
>O VI + Lyβ + C II from Starburst and Poststarburst Galaxies. I. Stellar Library and Evolutionary Synthesis Profiles
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O VI + Lyβ + C II from Starburst and Poststarburst Galaxies. I. Stellar Library and Evolutionary Synthesis Profiles
Evolutionary synthesis models of a stellar population in the far-ultraviolet are presented. The spectra include the lines O VI λλ1032, 1038, Lyβ, and C II λλ1036, 1037. They are based on a stellar library built with observations of O and B stars collected with Copernicus and the Hopkins Ultraviolet Telescope (HUT). This library is used as input into an evolutionary synthesis code. The line profile of O VI + Lyβ + C II is computed for different star formation histories (instantaneous burst and continuous star formation) and different assumptions about the initial mass function (IMF). The metallicity is near the solar value. O VI λλ1032, 1038 is a very sensitive indicator of the presence or absence of O stars. O VI develops a P Cygni profile when formed in stellar winds of the most massive stars. When these stars are absent, no O VI is formed. In contrast, Lyβ and C II are very sensitive indicators for B stars. If these stars dominate, as is the case in poststarburst galaxies, Lyβ and C II are present as strong absorption features, and they are formed in the photosphere of B stars. An equivalent width of Lyβ + C II larger than 1 ? always indicates a population younger than 1 Gyr. Because of the universal strength of O VI in O stars, O VI is not a good discriminator between instantaneous versus continuous star formation for ages in the starburst phase, but the absence of O VI and the presence of stellar Lyβ and C II is a good indicator of a short burst duration and for the galaxy being in a poststarburst phase. Application of this technique to starburst or poststarburst galaxies will require careful attention to interstellar absorption.
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机译:提出了远紫外线恒星种群的进化综合模型。光谱包括线O VI λλ1032、1038,Lyβ和C II λλ1036、1037。它们基于一个恒星库,该库是用哥白尼和霍普金斯紫外线望远镜(HUT)收集的O和B星观测建立的。该库用作进化综合代码的输入。针对不同的恒星形成历史(瞬时爆发和连续恒星形成)以及关于初始质量函数(IMF)的不同假设,计算了O VI +Lyβ+ C II的线廓。金属性接近太阳值。 O VI λλ1032、1038是O星星存在与否的非常敏感的指示。当在最大质量恒星的恒星风中形成时,O VI会形成P Cygni轮廓。当这些恒星不存在时,不会形成O VI。相反,Lyβ和C II对B星非常敏感。如果这些恒星占主导地位(如爆发后星系中的情况),则Lyβ和C II作为强吸收特征存在,它们形成在B星的光球中。 Lyβ+ C II的等效宽度大于1?始终表示小于1 Gyr的人口。由于O VI在O星中具有普遍强度,因此O VI不能很好地区分星爆阶段年龄的瞬时恒星形成与连续恒星形成,但是O VI的缺乏以及恒星Lyβ和C II的存在是一个很好的选择短暂的爆发持续时间和星系处于后爆发阶段的指示。将该技术应用于星爆或星爆后星系将需要仔细注意星际吸收。
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