Lyalpha发射星系的物理性质：不仅仅是原始星系？
The physical properties of Lyalpha emitting galaxies: not just primeval galaxies?
摘要：
我们分析了从GOODS-S场选取的z =3.5到z=6的LBG样品，作为B，V和i-脱落物，并且光谱观测表明它们具有Lyalpha发射线。我们的主要目的是研究它们的物理性质及其对发射线特征的依赖性，揭示Lyalpha发射星系与一般LBG群体之间的关系。这些天体是从它们的连续色中选择的，然后通过GOODS合作和其他活动进行光谱确认。从光谱中，我们推导出线通量和EW。然后利用GOODS-MUSIC的U波段到中红外测光数据，通过标准的SED拟合技术，得到星系的物理性质，如恒星总质量、年龄等，虽然大多数星系都能用年轻的恒星星族拟合，但也有一小部分星系具有SED，需要相当老的恒星成分，最高可达1 Gyr。年龄和EW之间没有明显的关系：一些最古老的星系有大的EW，也应该选择在窄带调查。因此，并非所有Lyalpha发射体都是形成早期的原始星系，就像通常假设的那样。我们还发现了大范围的恒星星族，质量从5 × 10^8 Msol到5 × 10^10 Msol，SFR从几个到60 Msol/年。虽然没有质量和EW之间的相关性，我们发现一个显着缺乏大规模的星系高EW，这可以解释，如果最大的星系更多的尘埃和/或包含更多的中性气体比质量较低的对象。最后，我们发现，超过一半的星系含有少量但不可忽略的尘埃：平均E（B-V）和EW是很好的相关性，虽然有一个大的散射，已经发现在较低的红移
英文摘要：
We have analyzed a sample of LBGs from z =3.5 to z=6 selected from the GOODS-S field as B,V and i-dropouts, and with spectroscopic observations showing that they have the Lyalpha line in emission. Our main aim is to investigate their physical properties and their dependence on the emission line characteristics, to shed light on the relation between galaxies with Lyalpha emission and the general LBG population.The objects were selected from their continuum colors and then spectroscopically confirmed by the GOODS collaboration and other campaigns. From the spectra we derived the line flux and EW. We then used U-band to mid-IR photometry from GOODS-MUSIC to derive the physical properties of the galaxies, such as total stellar mass, age and so on, through standard SED fitting techniques.Although most galaxies are fit by young stellar populations, a small but non negligible fraction has SEDs that require considerably older stellar component, up to 1 Gyr. There is no apparent relation between age and EW: some of the oldest galaxies have large EW, and should be also selected in narrow band surveys. Therefore not all Lyalpha emitters are primeval galaxies in the very early stages of formation,as is commonly assumed. We also find a large range of stellar populations, with masses from 5x10^8 Msol to 5x10^10 Msol and SFR from few to 60 Msol/yr. Although there is no correlation between mass and EW, we find a significant lack of massive galaxies with high EW, which could be explained if the most massive galaxies were more dusty and/or contained more neutral gas than less massive objects. Finally we find that more than half of the galaxies contain small but non negligible amounts of dust: the mean E(B-V) and the EW are well correlated, although with a large scatter, as already found at lower redshift
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