椭球体中倾斜梯度斜率与质量的关系：整体模型的预测
Abundance gradient slopes versus mass in spheroids: predictions by monolithic models
摘要：
我们调查是否有可能解释的早期类型的星系在整体模型的框架内观察到的梯度范围很广。为此，我们扩展了Pipino等人（2008 a）的流体动力学模拟，包括低质量椭圆星系和螺旋（真实）凸起。这些模型满足质量-金属丰度和质量-[α/Fe]关系。我们的模型预测的典型金属丰度梯度的斜率为-0.3 dex每十年的半径变化，与几个观测样本的平均值一致。然而，我们也发现了一些相当大的星系，其中这个斜率是-0.5德克斯每十年，与最近的一些数据一致。特别地，当我们将恒星丰度梯度转换成Mg_2线强度指数的径向变化时，我们发现了对质量示踪剂的轻微依赖，但在Mg_b中没有。我们的结论是，而不是一个质量斜率的关系，是更合适的说，在散射的梯度斜率与银河系质量的增加。我们可以解释这样的行为与不同的恒星形成效率的框架内修订的整体形成的情况下，因此，分散在所观察到的梯度不应该被用来作为证据的需要合并。事实上，表现出最陡梯度斜率的模型星系优先是那些在给定质量下具有最高恒星形成效率的星系。
英文摘要：
We investigate whether it is possible to explain the wide range of observed gradients in early type galaxies in the framework of monolithic models. To do so, we extend the set of hydrodynamical simulations by Pipino et al. (2008a) by including low-mass ellipticals and spiral (true) bulges. These models satisfy the mass-metallicity and the mass-[alpha/Fe] relations. The typical metallicity gradients predicted by our models have a slope of -0.3 dex per decade variation in radius, consistent with the mean values of several observational samples. However, we also find a few quite massive galaxies in which this slope is -0.5 dex per decade, in agreement with some recent data. In particular, we find a mild dependence from the mass tracers when we transform the stellar abundance gradients into radial variations of the Mg_2 line-strength index, but not in the Mg_b. We conclude that, rather than a mass- slope relation, is more appropriate to speak of an increase in the scatter of the gradient slope with the galactic mass. We can explain such a behaviour with different efficiencies of star formation in the framework of the revised monolithic formation scenario, hence the scatter in the observed gradients should not be used as an evidence of the need of mergers. Indeed, model galaxies that exhibit the steepest gradient slopes are preferentially those with the highest star formation efficiency at that given mass.
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。
