Observing the signature of accretion from the intergalactic medium ( IGM ) onto galaxies at z \sim 3 requires the detection of faint ( L \ll L ^ { * } ) galaxies embedded in a filamentary matrix of low-density ( \rho < 100 \overline { \rho } ) , metal-poor gas ( Z \sim 10 ^ { -2.5 } Z _ { \odot } ) coherent over hundreds of kpc .
We study the gaseous environment of three Ly \alpha emitters ( LAEs ) at z = 2.7 - 2.8 , found to be aligned in projection with a background QSO over \sim 250 kpc along the slit of a long-slit spectrum .
The lack of detection of the LAEs in deep continuum images and the low inferred Ly \alpha luminosities show the LAEs to be intrinsically faint , low-mass galaxies ( L \lesssim 0.1 L ^ { * } , M _ { \mathrm { star } } \lesssim 0.1 M ^ { * } ) .
An echelle spectrum of the QSO reveals strong Ly \alpha absorption within \pm 200 km s { { } ^ { -1 } } from the LAEs .
Our absorption line analysis leads to \ion HI column densities in the range of log N \mathrm { ( \ion { H } { I } ) } / \mbox { $ { cm ^ { -2 } } $ } = 16 - 18 .
Associated absorption from ionic metal species \ion CIV and \ion SiIV constrains the gas metallicities to \sim 0.01 solar if the gas is optically thin , and possibly as low as \sim 0.001 solar if the gas is optically thick , assuming photoionization equilibrium .
While the inferred metallicities are at least a factor of ten lower than expected metallicities in the interstellar medium ( ISM ) of these LAEs , they are consistent with the observed chemical enrichment level in the IGM at the same epoch .
Total metal abundances and kinematic arguments suggest that these faint galaxies have not been able to affect the properties of their surrounding gas .
The projected spatial alignment of the LAEs , together with the kinematic quiescence and correspondence between the LAEs and absorbing gas in velocity space suggests that these observations probe a possible filamentary structure .
Taken together with the blue-dominant Ly \alpha emission line profile of one of the objects , the evidence suggests that the absorbing gas is part of an accretion stream of low-metallicity gas in the IGM .