We calculate Lyman Alpha Emitter (LAE) angular correlation functions (ACFs) at $z simeq 6.6$ and the fraction of lifetime (for the 100 Myrs preceding $zsimeq6.6$) galaxies spend as Lyman Break Galaxies (LBGs) or as LBGs with Lyman Alpha (Ly$alpha$) e
mission using a model that combines SPH cosmological simulations (GADGET-2), dust attenuation and a radiative transfer code (pCRASH). The ACFs are a powerful tool that significantly narrows the 3D parameter space allowed by LAE Ly$alpha$ and UV luminosity functions (LFs) alone. With this work, we simultaneously constrain the escape fraction of ionizing photons $f_{esc}=0.05-0.5$, the mean fraction of neutral hydrogen in the intergalactic medium (IGM) $langle chi_{HI} rangle leq 0.01$ and the dust-dependent ratio of the escape fractions of Ly$alpha$ and UV continuum photons $f_{alpha}/f_c=0.6-1.2$. Our results show that reionization has the largest impact on the amplitude of the ACFs, and its imprints are clearly distinguishable from those of $f_{esc}$ and $f_alpha/f_c$. We also show that galaxies with a critical stellar mass of $M_* = 10^{8.5} (10^{9.5})M_{odot}$ produce enough luminosity to stay visible as LBGs (LAEs). Finally, the fraction of time during the past 100 Myrs prior to z=6.6 a galaxy spends as a LBG or as a LBG with Ly$alpha$ emission increases with the UV magnitude (and the stellar mass $M_*$): considering observed (dust and IGM attenuated) luminosities, the fraction of time a galaxy spends as a LBG (LAE) increases from 65% to 100% (0-100%) as $M_{UV}$ decreases from $M_{UV} = -18.0$ to $-23.5$ ($M_*$ increases from $10^8-10^{10.5} M_{odot}$). Thus in our model the brightest (most massive) LBGs most often show Ly$alpha$ emission.
We build a physical model for high-redshift Lyman Alpha emitters (LAEs) by coupling state of the art cosmological simulations (GADGET-2) with a dust model and a radiative transfer code (pCRASH). We post-process the cosmological simulation with pCRASH
using five different values of the escape fraction of hydrogen ionizing photons (f_esc=0.05,0.25,0.5,0.75,0.95) until reionization is complete, i.e. the average neutral hydrogen fraction drops to <X_HI>~10^-4. Then, the only free-parameter left to match model results to the observed Lya and UV luminosity functions of LAEs at z~6.6 is the relative escape of Lyman Alpha (Lya) and continuum photons from the galactic environment (f_alpha/f_c). We find a three-dimensional degeneracy such that the theoretical model can be reconciled with observations for an IGM Lya transmission <T_alpha>_LAE~38-50% (which translates to <X_HI>~0.5-10^-4 for Gaussian emission lines), f_esc~0.05-0.50 and f_alpha/f_c~0.6-1.8.
We consider a relativistically moving blob consisting of an isotropic electron distribution that Compton-scatters photons from an external isotropic radiation field. We compute the resulting beaming pattern, i.e. the distribution of the scattered pho
tons, in the blob frame as well as in the observers frame by using the full Klein-Nishina cross section and the exact incident photon distribution. In the Thomson regime the comparison of our approach with Dermer 1995 results in concurrent characteristics but different absolute number of the scattered photons by a factor of f_corr = 3.09. Additionally, our calculation yields a slightly lower boost factor which varies the more from the corresponding value in Dermer 1995 the higher the spectral index p of the electron distribution gets.
