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arXiv 0806.2410astro-ph
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AMAZE。I. z>3时质量-金属丰度关系的演化

AMAZE. I. The evolution of the mass-metallicity relation at z>3

R. Maiolino, T. Nagao, A. Grazian, F. Cocchia, A. Marconi, F. Mannucci, A. Cimatti, A. Pipino, S. Ballero, F. Calura, C. Chiappini, A. Fontana, G. L. Granato, F… 展开作者

R. Maiolino, T. Nagao, A. Grazian, F. Cocchia, A. Marconi, F. Mannucci, A. Cimatti, A. Pipino, S. Ballero, F. Calura, C. Chiappini, A. Fontana, G. L. Granato, F. Matteucci, G. Pastorini, L. Pentericci, G. Risaliti, M. Salvati, L. Silva

摘要:

我们目前的ESO-VLT大型计划(AMAZE)的初步结果,旨在确定的质量-金属丰度关系的演变,在z>3,通过深近红外光谱。气体金属丰度的测量,为初始样本的9个恒星形成星系在z~3.5,通过光学星云线红移到近红外。恒星质量准确地确定使用Spitzer-IRAC数据,其中采样的静止帧近红外恒星光在这些遥远的星系。与以前的调查相比,在z~3.5处推断的质量-金属丰度关系显示出比在较低红移处观察到的更强的演化。这种演化即使在大质量星系中也是显著的,表明z~3是大质量星系在恒星形成和金属富集方面的主要作用时期。也有迹象表明,低质量星系的金属丰度演化相对于高质量系统更强,这种效应可以被认为是星系缩小的化学版本。在z~3.5处观察到的质量-金属丰度关系与一些等级演化模型的预测很难调和。这种差异表明,在z>3的星系中,大部分是由相对未演化的子单位组成的,即恒星形成效率低的小星系。大部分的恒星形成和金属丰度演化可能发生在小星系已经组装成更大的系统之后。

英文摘要:

We present initial results of an ESO-VLT large programme (AMAZE) aimed at determining the evolution of the mass-metallicity relation at z>3 by means of deep near-IR spectroscopy. Gas metallicities are measured, for an initial sample of nine star forming galaxies at z~3.5, by means of optical nebular lines redshifted into the near-IR. Stellar masses are accurately determined by using Spitzer-IRAC data, which sample the rest-frame near-IR stellar light in these distant galaxies. When compared with previous surveys, the mass-metallicity relation inferred at z~3.5 shows an evolution much stronger than observed at lower redshifts. The evolution is prominent even in massive galaxies, indicating that z~3 is an epoch of major action in terms of star formation and metal enrichment also for massive systems. There are also indications that the metallicity evolution of low mass galaxies is stronger relative to high mass systems, an effect which can be considered the chemical version of the galaxy downsizing. The mass-metallicity relation observed at z~3.5 is difficult to reconcile with the predictions of some hierarchical evolutionary models. Such discrepancies suggest that at z>3 galaxies are assembled mostly with relatively un-evolved sub-units, i.e. small galaxies with low star formation efficiency. The bulk of the star formation and metallicity evolution probably occurs once small galaxies are already assembled into bigger systems.

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