标题： 高红移Damped Ly-α星系的质量-金属丰度关系 显示英文标题

标题： The mass-metallicity relation for high-redshift damped Ly-alpha galaxies

摘要： 我们利用欧洲南方天文台（ESO）VLT-UVES望远镜观测的类星体光谱数据库，构建了一个包含67个红移范围为1.7<zabs<3.7的强引力透镜吸收线（DLA）系统的样本。 对于每个系统，我们测量了相对于太阳的平均金属丰度[X/H]（其中X可以是Zn、S或Si），以及低电离线轮廓的速度宽度W1。 我们发现这两个量之间存在紧密的相关性，且该相关性的显著性达到了5σ水平。 在超过两个数量级的金属丰度范围内存在这种相关性，很可能是由于导致DLA吸收线的星系的质量-金属丰度关系所决定的。 最佳拟合的线性关系为[X/H]=1.35(\pm 0.11)\log W1 -3.69(\pm 0.18)，其中W1以km/s为单位表示。 尽管在这个速度-金属丰度关系中，高红移和低红移子样本的斜率在误差范围内相同，但有迹象表明随着红移减小，关系的截距点有所增加。 这表明具有给定质量的星系晕随着时间推移会变得更加富含金属。 此外，这个关系的斜率与本地星系的亮度-金属丰度关系一致。 因此，DLA系统中的最低金属丰度对应于具有最低质量的星系。 反过来，这些星系应该在DLA星系群体中具有最低的亮度。 这可能解释了最近的结果，即少数被探测到Lyα发射的DLA系统具有高于平均水平的金属丰度。 显示英文摘要

摘要： We used our database of ESO VLT-UVES spectra of quasars to build up a sample of 67 Damped Lyman-alpha (DLA) systems with redshifts 1.7<zabs<3.7. For each system, we measured average metallicities relative to Solar, [X/H] (with either X=Zn, S or Si), and the velocity widths of low-ionization line profiles, W1. We find that there is a tight correlation between the two quantities, detected at the 5sigma significance level. The existence of such a correlation, over more than two orders of magnitude spread in metallicity, is likely to be the consequence of an underlying mass-metallicity relation for the galaxies responsible for DLA absorption lines. The best-fit linear relation is [X/H]=1.35(\pm 0.11)\log W1 -3.69(\pm 0.18)$ with W1 expressed in km/s. While the slope of this velocity-metallicity relation is the same within uncertainties between the higher and the lower redshift bins of our sample, there is a hint of an increase of the intercept point of the relation with decreasing redshift. This suggests that galaxy halos of a given mass tend to become more metal-rich with time. Moreover, the slope of this relation is consistent with that of the luminosity-metallicity relation for local galaxies. The DLA systems having the lowest metallicities among the DLA population would therefore, on average, correspond to the galaxies having the lowest masses. In turn, these galaxies should have the lowest luminosities among the DLA galaxy population. This may explain the recent result that the few DLA systems with detected Ly-alpha emission have higher than average metallicities.