Ages and metallicities of central and satellite galaxies: implications for galaxy formation and evolution
Ages and metallicities of central and satellite galaxies: implications for galaxy formation and evolution
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DOI：
10.1111/j.1365-2966.2010.17074.x
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发表时间：
2009-12
影响因子：
4.8
通讯作者：
A. Pasquali;A. Gallazzi;F. Fontanot;F. V. D. Bosch;G. Lucia;H. Mo;Xiaohu Yang
中科院分区：
文献类型：
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作者：
A. Pasquali;A. Gallazzi;F. Fontanot;F. V. D. Bosch;G. Lucia;H. Mo;Xiaohu Yang
利用Gallazzi等人获得的斯隆数字巡天(SDSS)中星系的恒星年龄和金属丰度。和Yang等人的SDSS星系表，我们研究了中心星系和卫星星系的恒星年龄和金属度与恒星质量M(*)和晕质量M(H)的关系。我们发现，与相同恒星质量的中心相比，卫星更老，金属更丰富，而且这种差异随着M(*)的减小而增大。此外，年龄-恒星质量和金属丰度-恒星质量关系的斜率在密度更大的环境(更大质量的晕)中被发现变得更浅。这是由于低质量卫星星系(M(*)小于或类似于1010h-2M(圆点))的平均年龄和金属丰度随着其所在晕的质量而增加。为了了解这些趋势的物理根源，我们将我们的结果与Wang等人的半解析模型进行了比较。该模型预测了恒星质量函数和两点相关函数，总体上与观测结果吻合得很好，还再现了卫星比相同恒星质量的中心更老，年龄差异随着卫星晕质量的增加而增大的事实。这是因为卫星在被宿主光环吸积后不久就被剥夺了热气库(扼杀)。随之而来的恒星形成的猝灭使得恒星群体的卫星被动地进化，而中央恒星形成活动的延长使它们的平均年龄保持在更年轻的年龄。在质量更大的环境中，由此产生的年龄偏差更大，因为它们的卫星被吸积得更早。该模型没有再现低质量卫星金属度的晕质量依赖关系，给出了太浅的金属度-恒星质量和年龄-恒星质量关系，并预测卫星星系与相同恒星质量的中心具有相同的金属度，这与数据不一致。我们认为，这些差异可能表明需要(I)修改超新星反馈和活动星系核反馈的配方，(Ii)使用更现实的扼杀描述，以及(Iii)包括对卫星星系的潮汐剥离、加热和破坏的适当处理。
Using the stellar ages and metallicities of galaxies in the Sloan Digital Sky Survey (SDSS) obtained by Gallazzi et al. and the SDSS galaxy group catalogue of Yang et al., we study how the stellar ages and metallicities of central and satellite galaxies depend on stellar mass, M(*), and halo mass, M(h). We find that satellites are older and metal richer than centrals of the same stellar mass, and this difference increases with decreasing M(*). In addition, the slopes of the age-stellar mass and metallicity-stellar mass relations are found to become shallower in denser environments (more massive haloes). This is due to the fact that the average age and metallicity of low-mass satellite galaxies (M(*) less than or similar to 1010 h-2 M(circle dot)) increase with the mass of the halo in which they reside. In order to gain understanding of the physical origin of these trends, we compare our results with the semi-analytical model of Wang et al. The model, which predicts stellar mass functions and two-point correlation functions in good overall agreement with observations, also reproduces the fact that satellites are older than centrals of the same stellar mass and that the age difference increases with the halo mass of the satellite. This is a consequence of the fact that satellites are stripped of their hot gas reservoir shortly after they are accreted by their host haloes (strangulation). The ensuing quenching of star formation leaves the stellar populations of satellites to evolve passively, while the prolonged star formation activity of centrals keeps their average ages younger. The resulting age offset is larger in more massive environments because their satellites were accreted earlier. The model does not reproduce he halo mass dependence of the metallicities of low-mass satellites, yields metallicity-stellar mass and age-stellar mass relations that are too shallow and predicts that satellite galaxies have the same metallicities as centrals of the same stellar mass, in disagreement with the data. We argue that these discrepancies are likely to indicate the need to (i) modify the recipes of both supernova feedback and active galactic nucleus feedback, (ii) use a more realistic description of strangulation and (iii) include a proper treatment of the tidal stripping, heating and destruction of satellite galaxies.