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

扩展的巨Ly α发射体（Ly α Blobs，LAB）是最近才发现的一类新的天体，它是一种红移大于10 kpc的高红移Ly α发射体。有一些重要的物体，因为我们可能正在白化大质量星系的形成过程。虽然以前只知道有几个LABs的大小为100- 200 kpc，我们最近的研究揭示了超过70 LABs的大小为30- 200 kpc的大规模密度峰的Ly a发射体在z=3.1。在此基础上，我们进一步开展了以下研究：（i）开展更深更宽视场的窄带成像调查，研究大量Ly α辐射源，特别是LABs的分布和性质;（ii）通过制作一个新的NB滤波器，观测到z= 2.4的低红移辐射源（2005-2006）我们获得了z= 3.1Ly α发射体（LAEs）的最宽深窄带图像，并对其进行了分析，以研究LAEs在几个10 Mpc尺度上的分布和密度增强，寻找LABs，并研究了具有很大Ly α等效宽度的LAEs的性质。所得结果如下。(1)We评价了在z=3.1处观察到的密度峰值的显著性，发现它确实是一个非常罕见的大尺度过密区域。观测到这种大尺度超密度的概率很低，这意味着在高红移LAEs的形成中存在着一些未知的大尺度偏置机制。(2)巨LAB只在大尺度密度峰内部或附近频繁地被观测到，这意味着过密区确实是一个“星系形成区”，在那里星系的形成是优先发生的。（3）具有大等效宽度的LAE也强烈地集中在高密度峰区。

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.