在等级宇宙进化论中再现大质量星系的集合
Reproducing the assembly of massive galaxies within the hierarchical cosmogony
摘要：
为了深入了解恒星形成及其在星系中聚集的物理机制，我们将MORGANA与GRASIL分光光度模型相结合，将MORGANA模型的预测结果与K-和850 μ m选择星系的性质（如数计数、红移分布和光度函数）进行了比较。我们发现，这是可能的，以重现K-和850微米波段的数据集在同一时间，并与标准的萨尔彼得IMF，并归因于这一成功，我们改进的DM晕冷却建模。然后，我们预测，大规模的恒星形成盘在z~2处很常见，并主导着恒星形成率，但它们中的大多数在~ 1亿年内与其他星系合并。我们的首选模型在z<1处产生了过多的明亮星系;这种过多可能与星系团中弥漫恒星成分的积累有关，正如Monaco et al.（2006）所建议的那样，但是该论文中提出的机制的天真实现并没有产生足够的减缓这些物体的演化。此外，我们的模型高估了在z~1处10^{10}-10 11} M_sun星系的数量;这是Fontana et al.（2006）所示的理论模型的常见行为。这些发现表明，虽然星系形成模型正确地再现了恒星质量的总体积累，但星系的“缩小”趋势尚未完全再现。这暗示了一些缺失的反馈机制，以便同时再现大质量和小星系的形成。
英文摘要：
In order to gain insight into the physical mechanisms leading to the formation of stars and their assembly in galaxies, we compare the predictions of the MOdel for the Rise of GAlaxies aNd Active nuclei (MORGANA) to the properties of K- and 850 micron-selected galaxies (such as number counts, redshift distributions and luminosity functions) by combining MORGANA with the spectrophotometric model GRASIL. We find that it is possible to reproduce the K- and 850 micron-band datasets at the same time and with a standard Salpeter IMF, and ascribe this success to our improved modeling of cooling in DM halos. We then predict that massively star-forming discs are common at z~2 and dominate the star-formation rate, but most of them merge with other galaxies within ~100 Myr. Our preferred model produces an overabundance of bright galaxies at z<1; this overabundance might be connected to the build-up of the diffuse stellar component in galaxy clusters, as suggested by Monaco et al. (2006), but a naive implementation of the mechanism suggested in that paper does not produce a sufficient slow-down of the evolution of these objects. Moreover, our model over-predicts the number of 10^{10}-10^{11} M_sun galaxies at z~1; this is a common behavior of theoretical models as shown by Fontana et al. (2006). These findings show that, while the overall build-up of the stellar mass is correctly reproduced by galaxy formation models, the ``downsizing'' trend of galaxies is not fully reproduced yet. This hints to some missing feedback mechanism in order to reproduce at the same time the formation of both the massive and the small galaxies.
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