![](https://d3ilqtpdwi981i.cloudfront.net/EEyoheRFWcNniK8IE-X8FzOuKP0=/425x550/smart/https://bepress-attached-resources.s3.amazonaws.com/uploads/2f/d0/a5/2fd0a5c6-810f-4fd4-ab70-d8d351e2e6b3/thumbnail_BPFile%20object.jpg)
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.
Available at: http://works.bepress.com/todd_tripp/2/
DOI: 10.1086/592273
This is the pre-published version harvest from arXiv. The published version is located at http://arxiv.org/abs/0808.0921