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arXiv 0909.4735astro-ph.GA
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扰动蓝色致密星系UM 420和UM 462的VLT VIMOS积分场光谱研究

A VLT VIMOS integral field spectroscopic study of perturbed blue compact galaxies: UM 420 and UM 462

B. L. James, Y. G. Tsamis, M. J. Barlow

摘要:

我们报告了两个不相关的蓝色致密星系的光学积分场光谱,它们是用分辨率为0.33 x 0.33 arcsec ^2的13 x 13 arcsec ^2 VIMOS积分场单位绘制的。给出了在[O III] 5007、H-α和[N II] 6584光下的连续谱和扣除背景的发射谱线图。这两个星系都显示出正在进行的扰动和/或相互作用的迹象。UM 420首次被解析为由两个星爆式分量组成的合并系统,其中最大的分量具有“臂状”结构。UM 462是一个不规则形态的破裂系统,被分解成至少四个星爆区。图的H-α径向速度和半高宽进行了讨论。由于发射线仅与单一高斯分布拟合良好,因此在两个星系中都没有检测到潜在的宽线区域。电子温度和密度以及氦,氧,氮和硫的丰度计算光谱集成在整个星系和最近的恒星形成的每一个领域。地图的O/H比:这些星系显示的氧丰度是太阳的~ 20%。没有证据表明星系之间存在大量的丰度变化,这将指向显着的氮或氧自我富集(<0.2 dex极限)。与以前的观测结果相反,这种分析并不支持这些BCGs作为沃尔夫-拉叶星系的分类,因为在我们的光谱中没有检测到特征性的宽发射线特征。Baldwin-Phillips-Terlevich发射线比率图是在逐像素的基础上构建的,表明这些系统的光谱主要由恒星光电离激发。

英文摘要:

We report on optical integral field spectroscopy of two unrelated blue compact galaxies mapped with the 13 x 13 arcsec^2 VIMOS integral field unit at a resolution of 0.33 x 0.33 arcsec^2. Continuum and background subtracted emission line maps in the light of [O III] 5007, H-alpha, and [N II] 6584 are presented. Both galaxies display signs of ongoing perturbation and/or interaction. UM 420 is resolved for the first time to be a merging system composed of two starbursting components with an 'arm-like' structure associated with the largest component. UM 462 which is a disrupted system of irregular morphology is resolved into at least four starbursting regions. Maps of the H-alpha radial velocity and FWHM are discussed. No underlying broad line region was detected from either galaxy as the emission lines are well-fitted with single Gaussian profiles only. Electron temperatures and densities as well as the abundances of helium, oxygen, nitrogen, and sulphur were computed from spectra integrated over the whole galaxies and for each area of recent star formation. Maps of the O/H ratio are presented: these galaxies show oxygen abundances that are ~20 per cent solar. No evidence of substantial abundance variations across the galaxies that would point to significant nitrogen or oxygen self-enrichment is found (<0.2 dex limit). Contrary to previous observations, this analysis does not support the classification of these BCGs as Wolf-Rayet galaxies as the characteristic broad emission line features have not been detected in our spectra. Baldwin-Phillips-Terlevich emission line ratio diagrams which were constructed on a pixel by pixel basis indicate that the optical spectra of these systems are predominantly excited by stellar photoionization.

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