通过定制模型解开HII星系的金属丰度和恒星形成历史
Disentangling the metallicity and star formation history of HII galaxies through tailor-made models
摘要：
我们提出了一个自洽的研究的恒星星族和电离气体的样本中的10个HII星系，至少有四个测量的电子温度和离子丰度的精确测定以下的“直接方法”。我们使用STARLIGHT程序拟合了星系的光谱能量分布，以量化潜在的恒星星族对EW（Hbeta）的贡献，对于大多数物体来说，这一贡献约为10%。然后，我们研究了沃尔夫-拉叶恒星星族在七个星系中检测到的。这些星族的存在和校正后的EW（H β）值表明电离恒星星族是在一个持续时间为1000万年的连续恒星形成事件之后产生的，因此WR星可能存在于所有的天体中，即使它们在其中一些天体中没有被探测到。导出的恒星特征，电离光子数和最强发射线的相对强度被用作输入参数，计算定制的模型与光电离代码云。我们的模型是能够y再现他们的热和电离结构推导出碰撞激发的发射线，因此，没有丰度差异的因素，这类对象是隐含的。只有S+的电子温度被模型高估，指出这些物体中可能存在扩散气体的外壳。这种几何效应会影响到用依赖于低激发发射谱线的定标器测定电离团簇的等效有效温度。
英文摘要：
We present a self-consistent study of the stellar populations and the ionized gas in a sample of 10 HII galaxies with, at least, four measured electron temperatures and a precise determination of ionic abundances following the "direct method". We fitted the spectral energy distribution of the galaxies using the program STARLIGHT in order to quantify the contribution of the underlying stellar population to EW(Hbeta), which amounts to about 10% for most of the objects. We then studied the Wolf-Rayet stellar populations detected in seven of the galaxies. The presence of these populations and the corrected EW(Hbeta) values indicate that the ionizing stellar populations were created following a continuous star formation episode of 10 Myr duration, hence WR stars may be present in all of objects even if they are not detected in some of them. The derived stellar features, the number of ionizing photons and the relative intensities of the strongest emission lines were used as input parameters to compute tailored models with the photoionization code CLOUDY. Our models are able to y reproduce their thermal and ionization structure as deduced from their collisionally excited emission lines and, hence, no abundance discrepancy factors are implied for this kind of objects. Only the electron temperature of S+ is overestimated by the models, pointing to the possible presence of outer shells of diffuse gas in these objects. This kind of geometrical effects can affect the determination of the equivalent effective temperature of the ionizing cluster using calibrators which depend on low-excitation emission lines.
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