Synthetic Spectra of H Balmer and He I Absorption Lines. II. Evolutionary Synthesis Models for Starburst and Poststarburst Galaxies
Synthetic Spectra of H Balmer and He I Absorption Lines. II. Evolutionary Synthesis Models for Starburst and Poststarburst Galaxies
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H Balmer 和 He I 吸收线的合成光谱。
DOI：
10.1086/313285
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发表时间：
1999
期刊：
影响因子：
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通讯作者：
T. Heckman
中科院分区：
文献类型：
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作者：
R. G. González Delgado;C. Leitherer;T. Heckman
我们提出了演化恒星人口合成模型来预测光谱的单金属丰度恒星人口，光谱采样为0.3？在5个光谱区域之间的3700和5000？这些模型是针对有活跃星星形成的星系而优化的，它们综合了氢的Balmer系列的轮廓（Hβ、Hγ、Hδ、H8、H9、H10、H11、H12和H13）和中性氦吸收线（He I λ4922，He I λ4471，He I λ4388，He I λ4144，He I λ4121，He I λ4026，He I λ4009，和He I λ3819）的恒星初始质量函数（IMF）。给出了持续1 Gyr的连续星星形成模型。输入恒星库包括温度高于25，000 K的恒星的非LTE吸收剖面和温度较低的LTE剖面。温度和重力覆盖范围分别为4000 K ≤ Teff ≤ 50，000 K和0.0 ≤ log g ≤ 5.0。金属丰度是太阳能。它被发现，巴耳末和他我线的配置文件是敏感的年龄，除了在第一个4万年的演变，当这些线的等效宽度是恒定的。在这些演变的早期阶段，线条的轮廓对货币基金组织也很敏感。然而，强H巴耳末和他我线预测，即使低质量的国际货币基金组织的截止高达10 M。巴耳末线的等效宽度范围为2 - 16 μ m，He I线的等效宽度范围为0.2 - 1.2 μ m。在星云阶段（星系团年龄约为10 Myr），Hβ的范围为2至5 Å，He I λ4471的范围为0.5至1.2 Å。当簇是几百万年（对于巴尔末线）和几十万年（对于He I线）时，线的强度是最大的。在连续的星星形成的情况下，巴耳末线和He I线的强度随着时间单调增加，直到500和100万年，分别。然而，由于大质量恒星的贡献对巴耳末线和He I线的稀释，这些线比爆发模型中的弱。高光谱分辨率的配置文件是有用的，以重现吸收翼观察到的地区最近的星星形成和估计的影响，潜在的吸收星云发射线。与恒星吸收分量相比，星云发射的巴耳末和He I谱线的强度表明，如果一个瞬时爆发的年龄大于1.5亿年，那么Hδ和巴耳末级数的高阶项以及He I谱线都是由恒星吸收分量控制的。一些He I线（例如，He I λ3819和He I λ4922）比其它的（例如，He I λ4471），用于在星云辐射存在下探测恒星特征。我们估计，当He I λ4471星云的发射线的等效宽度在10 ~ 2.5 μ m之间（对应于爆发年龄在100 ~ 300万年之间）时，恒星吸收对该星云发射线的修正在5%~ 25%之间。该模型可用于日期星暴和poststarburst星系，直到1 Gyr。它们已经在大麦哲伦星系中的星团、星暴星系NGC 1569中的超级星团B、矮椭圆星系NGC 205的核心和一个发光的“E+A”星系的数据上进行了测试。完整的数据集可在我们的网站上检索或应作者的要求检索。
We present evolutionary stellar population synthesis models to predict the spectrum of a single-metallicity stellar population, with a spectral sampling of 0.3 Å in five spectral regions between 3700 and 5000 Å. The models, which are optimized for galaxies with active star formation, synthesize the profiles of the hydrogen Balmer series (Hβ, Hγ, Hδ, H8, H9, H10, H11, H12, and H13) and the neutral helium absorption lines (He I λ4922, He I λ4471, He I λ4388, He I λ4144, He I λ4121, He I λ4026, He I λ4009, and He I λ3819) for a burst with an age ranging from 106 to 109 yr, and different assumptions about the stellar initial mass function (IMF). Continuous star formation models lasting for 1 Gyr are also presented. The input stellar library includes non-LTE absorption profiles for stars hotter than 25,000 K and LTE profiles for lower temperatures. The temperature and gravity coverage is 4000 K ≤ Teff ≤ 50,000 K and 0.0 ≤ log g ≤ 5.0, respectively. The metallicity is solar. It is found that the Balmer and He I line profiles are sensitive to the age, except during the first 4 Myr of the evolution, when the equivalent widths of these lines are constant. At these early stages of the evolution, the profiles of the lines are also sensitive to the IMF. However, strong H Balmer and He I lines are predicted even when the low-mass cutoff of the IMF is as high as 10 M☉. The equivalent widths of the Balmer lines range from 2 to 16 Å and those of the He I lines from 0.2 to 1.2 Å. During the nebular phase (cluster younger than about 10 Myr), Hβ ranges from 2 to 5 Å and He I λ4471 ranges between 0.5 and 1.2 Å. The strength of the lines is maximum when the cluster is a few hundred (for the Balmer lines) and a few tens (for the He I lines) of Myr old. In the continuous star formation scenario, the strength of the Balmer and He I lines increases monotonically with time until 500 and 100 Myr, respectively. However, the lines are weaker than in the burst models owing to the dilution of the Balmer and He I lines by the contribution from very massive stars. The high spectral resolution of the profiles is useful to reproduce the absorption wings observed in regions of recent star formation and to estimate the effect of the underlying absorption on the nebular emission lines. The strength of the nebular emission Balmer and He I lines compared with the stellar absorption components indicates that Hδ and the higher order terms of the Balmer series and He I are dominated by the stellar absorption component if an instantaneous burst is older than ≃5 Myr. Some of the He I lines (e.g., He I λ3819 and He I λ4922) are more favorable than others (e.g., He I λ4471) for the detection of stellar features in the presence of nebular emission. We estimate that the correction to the He I λ4471 nebular emission line due to the stellar absorption is between 5% and 25%, if the nebular emission has equivalent width between 10 and 2.5 Å (corresponding to a burst age between 1 and 3 Myr). The models can be used to date starburst and poststarburst galaxies until 1 Gyr. They have been tested on data for clusters in the LMC, the super-star cluster B in the starburst galaxy NGC 1569, the nucleus of the dwarf elliptical NGC 205 and a luminous "E+A" galaxy. The full data set is available for retrieval at our websites or on request from the authors.