Extended Lyman Alpha Emission-Line Objects at High Redshift and Galaxy Formation

扩展的巨型Ly α发射体（Ly α Blobs， LAB）是最近才被发现的一个新类别，具有超过10 kpc扩展的高红移Ly α发射体。有一些重要的物体，因为我们可能正在粉饰大质量星系的形成过程。虽然以前已知的100-200kpc大小的实验室很少，但我们最近的研究表明，在z=3.1的Ly a发射体大尺度密度峰中存在70多个30-200kpc大小的实验室。在此基础上，我们扩展了我们的研究：(1)进一步进行深宽场窄带成像调查，研究大量Ly α发射体，特别是LABs的分布和性质；(2)通过制作新的NB滤波器，观察低红移z=2.4的发射体。在本项目资助期间（2005-2006），我们获得了z=3.1 Ly α发射体（LAEs）的最宽深窄带图像的新数据，并对其进行了分析，研究了LAEs在几个10Mpc尺度上的分布和密度增强，寻找实验室，并研究了具有非常大Ly α等效宽度的LAEs的性质。所得结果如下：(1)我们对观测到的密度峰在z=3.1处的显著性进行了评价，发现它确实是在大尺度密集区域上非常罕见的。观测到这种大尺度大过密度的概率极低，这意味着在高红移处LAEs形成的大尺度偏置应该存在某种未知的机制。(2)巨型实验室仅在大尺度密度峰内或附近频繁观测到，这表明过密区确实是一个“星系形成区”，优先发生星系的形成。(3)具有大等效宽度的LAEs也强烈集中在高密度峰区。

Extended giant Ly a emitters (Ly α Blobs, LAB), high-redshift Ly α emitters with extension of more than several 10 kpc are objects in a new category which were discovered only recently. There are important objects as we may be whitenessing the formation process of massive galaxies. While there were only a few LABs with 100-200kpc size known previously, our recent study revealed the presence of more than 70 LABs with size of 30-200kpc in the large-scale density peak of Ly a emitters at z=3.1. Based on the results, we expanded our study (i) to conduct further deep and wide-field narrow-band imaging survey to study the distribution and properties of a large number of Ly α emitters, especially LABs, and (ii) to observe emitters at lower redshift z=2.4by making a new NB filter.During the period of this grant (2005-2006) we obtained a new data of ever widest deep narrow-band images for z=3.1 Ly α emitters (LAEs) and analyzed it to study the distribution and density enhancement of LAEs over several 10Mpc scale, to search for LABs, and to study the properties of LAEs with very large Ly α equivalent width. The results obtained are as follows.(1)We evaluated the significance of the observed density peak at z=3.1 and found it is indeed a very rare over dense region of large scale. The probability that such large -scale large overdensity is observed is extremely low, which implies there should be some unknown mechanism of the large-scale bias in formation of LAEs at high redshift. (2) Giant LABs are only frequently observed inside or near the large-scale density peak which implies that the over-dense region is indeed a "galaxy-forming region" where formation of galaxies are preferentially occurring (3) LAEs with large equivalent width also strongly concentrated in the high-density peak region.