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arXiv 1506.03084astro-ph.GAastro-ph.CO
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大质量星系的z~3形态--见证两个核团生长通道

The morphologies of massive galaxies from z~3 - Witnessing the 2 channels of bulge growth

Marc Huertas-Company, Pablo G. Pérez-González, Simona Mei, Francesco Shankar, Mariangela Bernardi, Emanuele Daddi, Guillermo Barro, Guillermo Cabrera-Vives, And… 展开作者

Marc Huertas-Company, Pablo G. Pérez-González, Simona Mei, Francesco Shankar, Mariangela Bernardi, Emanuele Daddi, Guillermo Barro, Guillermo Cabrera-Vives, Andrea Cattaneo, Paola Dimauro, Romaric Gravet

摘要:

在5个CANDELS场中,我们对z~0质量星系($M*/M_\odot\sim10^{11}$)从z~3开始的形态演化进行了定量研究。使用丰度匹配技术选择祖细胞以解释质量生长。从z~3开始,形貌强烈演化。在z<1时,人口与哈勃序列的大质量端相匹配,其中30%的球状体,50%的星系具有同等主导的盘和凸起成分,20%的盘。在z~2-3处,存在大多数不规则系统(~60-70%),仍有30%的球状体。然后,我们独立地分析不同形态的SFR、气体分数和结构性质。我们的研究结果表明,两个不同的渠道增长的大质量星系的凸起。约30-40%在z~2.5处已经是凸起,具有低的平均SFR和气体分数(10-15%)、高的Sersic指数(n>3-4)和小的有效半径($R_e$ ~1 kpc),表明通过富含气体的合并或挤压形成早期地层。在z~ 2.5和z~0之间,它们的大小迅速增加~4-5倍,变得完全被动,但它们的整体形态保持不变。构造演化是独立的气体馏分,这表明它是由异位事件驱动。剩下的60%经历了一个逐渐的形态转变,从clubleshoot盘到更规则的bulge+disks系统,基本上发生在z>1。结果表明,2/3的系统可能通过团簇的迁移而形成了一个显著的凸起(n~3),而其余1/3的系统则保持了一个较小的凸起(n~1.5-2)。扰动和松弛系统之间的过渡阶段和隆起的出现与恒星形成活动和气体分数的减少有关。有效半径的增长大致与$H(z)^{-1}$成比例,因此与星系晕中圆盘的预期增长一致。

英文摘要:

[abridged] We quantify the morphological evolution of z~0 massive galaxies ($M*/M_\odot\sim10^{11}$) from z~3 in the 5 CANDELS fields. The progenitors are selected using abundance matching techniques to account for the mass growth. The morphologies strongly evolve from z~3. At z<1, the population matches the massive end of the Hubble sequence, with 30% of spheroids, 50% of galaxies with equally dominant disk and bulge components and 20% of disks. At z~2-3 there is a majority of irregular systems (~60-70%) with still 30% of spheroids. We then analyze the SFRs, gas fractions and structural properties for the different morphologies independently. Our results suggest two distinct channels for the growth of bulges in massive galaxies. Around 30-40% were already bulges at z~2.5, with low average SFRs and gas-fractions (10-15%), high Sersic indices (n>3-4) and small effective radii ($R_e$~1 kpc) pointing towards an early formation through gas-rich mergers or VDI. Between z~ 2.5 and z~0, they rapidly increase their size by a factor of ~4-5, become all passive but their global morphology remains unaltered. The structural evolution is independent of the gas fractions, suggesting that it is driven by ex-situ events. The remaining 60% experience a gradual morphological transformation, from clumpy disks to more regular bulge+disks systems, essentially happening at z>1. It results in the growth of a significant bulge component (n~3) for 2/3 of the systems possibly through the migration of clumps while the remaining 1/3 keeps a rather small bulge (n~1.5-2). The transition phase between disturbed and relaxed systems and the emergence of the bulge is correlated with a decrease of the star formation activity and the gas fractions. The growth of the effective radii scales roughly with $H(z)^{-1}$ and it is therefore consistent with the expected growth of disks in galaxy haloes.

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