探测成星矮星系UM 461和Mrk 600中贫金属气体的吸积
Detecting metal-poor gas accretion in the star-forming dwarf galaxies UM 461 and Mrk 600
摘要：
利用VIMOS-IFU观测，我们研究了两个成星矮星系UM 461和Mrk 600的星际介质（ISM）。我们的目的是寻找金属丰度不均匀性的存在，可能会出现从近原始气体进料正在进行本地化的恒星形成的下降。使用说明书的数据使我们能够研究外部气体吸积对这些星系的化学演化以及电离气体运动学和形态的影响。这两个系统都显示出形态扭曲的迹象，包括彗星状的形态。本文用直接法（T_e）和广泛应用的HII-CHI-mistry程序，以及采用不同的标准刻度，分析了两个星系中12 + log（O/H）丰度的空间变化。对于UM 461，我们的结果表明，ISM在大尺度上是相当好的混合，然而，我们使用直接方法在最亮的HII区域的SW部分发现了一个偏离中心的低金属丰度区域，12 + log（O/H）< 7.6。这一结果是一致的，最近的低质量的贫金属矮星或HI云到该地区现在表现出最低的金属丰度，这也显示本地化扰动中性和电离气体运动学。相比之下，Mrk 600在大尺度和小尺度上似乎都是化学均匀的。在我们分析的星系中的ISM的空间分辨特性的内在差异是一致的，这些系统处于不同的演化阶段。
英文摘要：
Using VIMOS-IFU observations, we study the interstellar medium (ISM) of two star-forming dwarf galaxies, UM 461 and Mrk 600. Our aim was to search for the existence of metallicity inhomogeneities that might arise from infall of nearly pristine gas feeding ongoing localized star-formation. The IFU data allowed us to study the impact of external gas accretion on the chemical evolution as well as the ionised gas kinematics and morphologies of these galaxies. Both systems show signs of morphological distortions, including cometary-like morphologies. We analysed the spatial variation of 12 + log(O/H) abundances within both galaxies using the direct method (T_e), the widely applied HII-CHI-mistry code, as well as by employing different standard calibrations. For UM 461 our results show that the ISM is fairly well mixed, at large scales, however we find an off-centre and low-metallicity region with 12 + log(O/H) < 7.6 in the SW part of the brightest HII region, using the direct method. This result is consistent with the recent infall of a low mass metal-poor dwarf or HI cloud into the region now exhibiting the lowest metallicity, which also displays localized perturbed neutral and ionized gas kinematics. Mrk 600 in contrast, appears to be chemically homogeneous on both large and small scales. The intrinsic differences in the spatially resolved properties of the ISM in our analysed galaxies are consistent with these systems being at different evolutionary stages.
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