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We calculate the impact of the intergalactic medium (IGM) on the observed Lyman alpha lines (hereafter Lya) emitted by galaxies in an ionised IGM at z>4. Our model accounts for gas clumping in the IGM and for the fact that high-redshift galaxies reside in overdense regions, which causes the velocity field of the IGM to depart from the Hubble flow. The observed shape of the Lya line varies widely, with dependence on the intrinsic width and systemic velocity of the line, a galaxies star formation rate and the local extra-galactic UV-background. For large star formation rates and levels of the UV-background, absorption in the IGM does not result in a Lya line that is asymmetric as is common among known high-redshift Lya emitters. For models in which the lines do show the observed strong asymmetry, the IGM typically transmits only 10-30% of the Lya flux. The increase in the ionising background that accompanied the completion of reionisation barely increased the IGM transmission, which suggests that LAEs of comparable luminosity should not appear to be significantly dimmer prior to overlap. In this light, we briefly discuss the potential of Lya emitters as a probe into the epoch of reionisation.
Recent results have shown that a substantial fraction of high-redshift Lyman alpha galaxies contain considerable amounts of dust. This implies that Lyman alpha galaxies are not primordial, as has been thought in the past. However, this dust has not b
With the Multi Unit Spectroscopic Explorer (MUSE), it is now possible to detect spatially extended Lyman alpha emission from individual faint (M_UV ~ -18) galaxies at redshifts, 3 < z < 6, tracing gas out to circum-galactic scales comparable to the d
A Near-infrared (1.18-1.35 micron) high-resolution spectrum of the gravitationally-lensed QSO APM 08279+5255 was obtained with the IRCS mounted on the Subaru Telescope using the AO system. We detected strong NaI D 5891,5897 doublet absorption in high
Population III galaxies, made partly or exclusively of metal-free stars, are predicted to exist at high redshifts and may produce very strong Lya emission. A substantial fraction of these Lya photons are likely absorbed in the intergalactic medium at
We present semi-analytical models of high redshift Lyman-{alpha} emitters (LAEs) in order to constrain the star formation efficiency in those galaxies. Our supernova feedback induced star formation model along with Sheth-Tormman halo mass function co