Large-scale Filamentary Structure around the Protocluster at Redshift   z=3.1
  We report the discovery of a large-scale coherent filamentary structure of Lyman alpha emitters in a redshift space at z=3.1. We carried out spectroscopic observations to map the three dimensional structure of the belt-like feature of the Lyman alpha emitters discovered by our previous narrow-band imaging observations centered on the protocluster at z=3.1. The feature was found to consist of at least three physical filaments connecting with each other. The result is in qualitative agreement with the prediction of the 'biased' galaxy-formation theories that galaxies preferentially formed in large-scale filamentary or sheet-like mass overdensities in the early Universe. We also found that the two known giant Lyman alpha emission-line nebulae showing high star-formation activities are located near the intersection of these filaments, which presumably evolves into a massive cluster of galaxies in the local Universe. This may suggest that massive galaxy formation occurs at the characteristic place in the surrounding large-scale structure at high redshift. 
Y. Matsuda, T. Yamada, T. Hayashino, H. Tamura, R. Yamauchi, T.   Murayama, T. Nagao, K. Ohta, S. Okamura, M. Ouchi, K. Shim...