Observations of the Gas Reservoir around a Star Forming Galaxy in the   Early Universe
  We present a high signal-to-noise spectrum of a bright galaxy at z = 4.9 in 14 h of integration on VLT FORS2. This galaxy is extremely bright, i_850 = 23.10 +/- 0.01, and is strongly-lensed by the foreground massive galaxy cluster Abell 1689 (z=0.18). Stellar continuum is seen longward of the Ly-alpha emission line at ~7100 \AA, while intergalactic H I produces strong absorption shortward of Ly-alpha. Two transmission spikes at ~6800 Angstroms (A) and ~7040 A are also visible, along with other structures at shorter wavelengths. Although fainter than a QSO, the absence of a strong central ultraviolet flux source in this star forming galaxy enables a measurement of the H I flux transmission in the intergalactic medium (IGM) in the vicinity of a high redshift object. We find that the effective H I optical depth of the IGM is remarkably high within a large 14 Mpc (physical) region surrounding the galaxy compared to that seen towards QSOs at similar redshifts. Evidently, this high-redshift galaxy is located in a region of space where the amount of H I is much larger than that seen at similar epochs in the diffuse IGM. We argue that observations of high-redshift galaxies like this one provide unique insights on the nascent stages of baryonic large-scale structures that evolve into the filamentary cosmic web of galaxies and clusters of galaxies observed in the present universe. 
Brenda L. Frye (1), David. V. Bowen (2), Mairead Hurley (1), Todd M.   Tripp (3), Xiaohui Fan (4), Bradley Holden (5), Purag...