LambdaCDM宇宙学中的星系形态
Galaxy morphology in the LambdaCDM cosmology
摘要：
我们调查的起源星系形态（定义为膨胀总K波段光度）在Lambda CDM宇宙学使用两个星系形成模型，基于千年模拟，由鲍尔等人（达勒姆模型）和德露西亚和布莱佐（MPA模型）。这两个模型对星系形态的预测有许多相似之处，但也有根本的分歧。例如，考虑到现有观测数据的不确定性，两者都产生了现实的形态组合，但其演变非常不同。这种差异和其他差异的一个主要原因是对盘不稳定性的处理，这在达勒姆模型中起着更突出的作用。我们的分析证实了以前的理论预测，即椭圆星系在星系大部分组装之前形成了大部分恒星。螺旋往往有较晚的“组装”时间作为一个结果，在原地恒星形成。除了最亮的椭圆星系（恒星质量> 2.5e ~（11）M_sun/h）外，我们发现主要的合并不是大多数椭球体（椭圆星系和螺旋凸起）聚集质量的主要机制。事实上，大多数椭圆星系（以及绝大多数螺旋星系）从未经历过重大的合并（高于我们模拟的分辨率限制）。大多数椭圆星系和螺旋星系通过较小的合并或盘的不稳定性获得它们的恒星质量。这些结论对两种模型都是相同的。在这些模型中，球体的旋转特性可能有助于限制盘不稳定性的重要性。
英文摘要：
We investigate the origins of galaxy morphology (defined by bulge-to-total K-band luminosity) in the LambdaCDM cosmology using two galaxy formation models ,based on the Millennium simulation, by Bower et al. (the Durham model) and De Lucia & Blaizot (the MPA model). There are many similarities, but also fundamental disagreements in the predictions of the two models for galaxy morphology. For example, taking into account uncertainties in the available observational data, both produce a realistic morphological mix today, but its evolution is very different. A main cause of this and other differences is the treatment of disk instabilities which play a more prominent role in the Durham model. Our analysis confirms previous theoretical predictions that elliptical galaxies form most of their stars before the bulk of the galaxy is assembled. Spirals tend to have later `assembly' times as a consequence of in-situ star formation. With the exception of the brightest ellipticals (stellar mass > 2.5e11 M_sun/h), we find that major mergers are not the primary mechanism by which most spheroids (ellipticals and spiral bulges) assemble their mass. In fact, the majority of ellipticals (and the overwhelming majority of spirals) never experience a major merger (above the resolution limit of our simulation.) Most ellipticals and spiral bulges acquire their stellar mass through minor mergers or disk instabilities. These conclusions are common to both models. The rotation properties of spheroids may help to constrain the importance of disk instabilities in these models.
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