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arXiv 1111.1392astro-ph.CO
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低金属丰度发射线星系的VLT光谱学:丰度图和丰度差异

VLT spectroscopy of low-metallicity emission-line galaxies: abundance patterns and abundance discrepancies

N. G. Guseva, Y. I. Izotov, G. Stasinska, K. J. Fricke, C. Henkel, P. Papaderos

摘要:

我们提出了一个大样本的低金属丰度发射线星系的深光谱。这项研究的主要目标是在这些低金属量星系的元素丰度。本文分析了46个低金属丰度发射线星系中HII区的121个VLT谱。这些光谱中的83个是档案VLT/FORS 1 +UVES光谱的HII区的31个低金属丰度的发射线星系,研究了第一次与标准的直接方法,以确定电子温度,电子数密度,和化学丰度。样品的氧丰度在12 + log O/H = 7.2-8.4的范围内。Ne/O比随着氧丰度的增加而增加。铁/氧比从最低金属丰度时的太阳能值下降到太阳能值的十分之一,表明铁在尘埃颗粒中的消耗程度取决于金属丰度。在12+logO/H<7.5的极低金属量星系中,N/O比随着氧丰度的降低而略有增加。本文首次给出了低金属丰度星系中电子温度的经验关系式,即由[SIII]6312/9069或[NII]5755/6583导出的电子温度与由[OIII]4363/(4959+5007)导出的电子温度之间的经验关系。在许多天体中,C^++和O^++的丰度可以从重组谱线中推导出来。我们的研究证实了从复合线(RL)和碰撞激发线(CEL)发现的丰度之间的差异,以及C/O随O/H增加。

英文摘要:

(abridged) We present deep spectroscopy of a large sample of low-metallicity emission-line galaxies. The main goal of this study is to derive element abundances in these low-metallicity galaxies. We analyze 121 VLT spectra of HII regions in 46 low-metallicity emission-line galaxies. 83 of these spectra are archival VLT/FORS1+UVES spectra of HII regions in 31 low-metallicity emission-line galaxies that are studied for the first time with standard direct methods to determine the electron temperatures, the electron number densities, and the chemical abundances. The oxygen abundance of the sample lies in the range 12 + log O/H = 7.2-8.4. The Ne/O ratio increases with increasing oxygen abundance. The Fe/O ratio decreases from roughly solar at the lowest metallicities to about one tenth of solar, indicating that the degree of depletion of iron into dust grains depends on metallicity. The N/O ratio in extremely low-metallicity galaxies with 12+logO/H<7.5 shows a slight increase with decreasing oxygen abundance. We present the first empirical relation between the electron temperature derived from [SIII]6312/9069 or [NII]5755/6583 and the one derived from [OIII]4363/(4959+5007) in low-metallicity galaxies. In a number of objects, the abundances of C^++ and O^++ could be derived from recombination lines. Our study confirms the discrepancy between abundances found from recombination lines (RLs) and collisionally excited lines (CELs) and that C/O increases with O/H.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

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