Clustering and lifetime of Lyman Alpha Emitters in the Epoch of Reionization

Abstract

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 $z\simeq 6.6$) galaxies spend as Lyman Break Galaxies (LBGs) or as LBGs with Lyman Alpha (Ly$\hat{I}\pm$) emission 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$\hat{I}\pm$ 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) $⟨\ddot{I}{‡}_{HI}⟩\le 0.01$ and the dust-dependent ratio of the escape fractions of Ly$\hat{I}\pm$ and UV continuum photons $f_{\hat{I}}\pm /f_c=0.6-1.2$. 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 $f_{\hat{I}}\pm /f_c$. We also show that galaxies with a critical stellar mass of $M_{\ast }=10^{8.5}(10^{9.5})M_{\odot }$ 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$\hat{I}\pm$ emission increases with the UV magnitude (and the stellar mass $M_{\ast }$): 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 $-23.5$ ($M_{\ast }$ increases from $10^8-10^{10.5}{M}_{\odot }$). Thus in our model the brightest (most massive) LBGs most often show Ly$\hat{I}\pm$ emission.

11 pages, 7 figures, accepted for publication in MNRAS, comments welcome