Ultraviolet Line Spectra of Metal-poor Star-forming Galaxies
Ultraviolet Line Spectra of Metal-poor Star-forming Galaxies
复制标题
贫金属恒星形成星系的紫外线光谱
DOI：
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发表时间：
2000
期刊：
影响因子：
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通讯作者：
C. Robert
中科院分区：
文献类型：
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作者：
C. Leitherer;J. Leão;T. Heckman;D. Lennon;M. Pettini;C. Robert
我们提出了合成的紫外光谱的贫金属恒星形成的星系，计算与Starburst 99包。一个新的光谱库是从哈勃太空望远镜对大麦哲伦星云和小麦哲伦星云中O型星的观测中产生的。合成光谱的相应平均金属丰度约为Z。光谱的分辨率为1 μ m，光谱范围为1200-1600 μ m。一组模型光谱计算的标准初始质量函数和星星形成的历史，并在太阳金属丰度合成光谱进行比较。我们发现，光谱线一般较弱，在较低的金属丰度，预期从较低的元素丰度。然而，恒星风线表现出更复杂的行为：电离平衡的金属丰度依赖性在痕量离子中可能很重要，如N4+和Si 3+。因此，NV λ1240和Si IV λ1400的强度并不与金属丰度单调成比例。我们比较我们的新模型的紫外光谱的NGC 5253和MS 1512-cB 58，两个恒星形成星系的四分之一的太阳金属丰度在低和高的红移，分别。与使用Z反馈库的早期模型相比，新库提供了更好的观测拟合。我们讨论了利用恒星光球和风线来估计恒星形成星系的化学成分的潜力。新的贫金属合成光谱可通过Starburst 99网站获得。
We present synthetic ultraviolet spectra of metal-poor star-forming galaxies that were calculated with the Starburst99 package. A new spectral library was generated from Hubble Space Telescope observations of O stars in the Large and Small Magellanic Clouds. The corresponding mean metallicity of the synthetic spectra is approximately Z☉. The spectra have a resolution of 1 Å and cover the spectral range 1200-1600 Å. A set of model spectra was calculated for a standard initial mass function and star formation history and is compared to synthetic spectra at solar metallicity. We find that the spectral lines are generally weaker at lower metallicity, as expected from the lower elemental abundances. Stellar wind lines, however, show a more complex behavior: the metallicity dependence of the ionization balance can be important in trace ions, like N4+ and Si3+. Therefore, the strength of N V λ1240 and Si IV λ1400 does not scale monotonically with metallicity. We compare our new models to ultraviolet spectra of NGC 5253 and MS 1512-cB58, two star-forming galaxies with one-fourth solar metallicity at low and high redshifts, respectively. The new library provides significantly better fits to the observations than earlier models using the Z☉ library. We discuss the potential of utilizing stellar photospheric and wind lines to estimate the chemical composition of star-forming galaxies. The new metal-poor synthetic spectra are available via the Starburst99 Web site.