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The redshift-dependent fraction of color-selected galaxies revealing Lyman alpha emission has become the most valuable constraint on the evolving neutrality of the early intergalactic medium. However, in addition to resonant scattering by neutral gas, the visibility of Lyman alpha is also dependent on the intrinsic properties of the host galaxy, including its stellar population, dust content and the nature of outflowing gas. Taking advantage of significant progress we have made in determining the line emitting properties of $z simeq 4-6$ galaxies, we propose an improved method, based on using the measured slopes of the rest-frame ultraviolet continua of galaxies, to interpret the growing body of near-infrared spectra of $z>7$ galaxies in order to take into account these host galaxy dependencies. In a first application of our new method, we demonstrate its potential via a new spectroscopic survey of $7<z<8$ galaxies undertaken with the Keck MOSFIRE spectrograph. Together with earlier published data our data provides improved estimates of the evolving visibility of Lyman alpha, particularly at redshift $zsimeq 8$. As a byproduct, we also present a new line emitting galaxy at a redshift $z=7.62$ which supersedes an earlier redshift record. We discuss the improving constraints on the evolving neutral fraction over $6<z<8$ and the implications for cosmic reionization.
Today, the majority of the cosmic baryons in the Universe are not observed directly, leading to an issue of missing baryons at low redshift. Cosmological hydrodynamical simulations have indicated that a significant portion of them will be converted i
We present results from seven cosmological simulations that have been extended beyond the present era as far as redshift $z=-0.995$ or $tapprox96,{rm Gyr}$, using the Enzo simulation code. We adopt the calibrated star formation and feedback prescript
The intergalactic medium is expected to clump on scales down to $10^4-10^8$ M$_{odot}$ before the onset of reionization. The impact of these small-scale structures on reionization is poorly understood despite the modern understanding that gas clumpin
During reionization, the intergalactic medium is heated impulsively by supersonic ionization fronts (I-fronts). The peak gas temperatures behind the I-fronts, $T_mathrm{reion}$, are a key uncertainty in models of the thermal history after reionizatio
We present the discovery of diffuse optical line emission in the Centaurus cluster seen with the MUSE IFU. The unparalleled sensitivity of MUSE allows us to detect the faint emission from these structures which extend well beyond the bounds of the pr