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

TL;DR

This study uses simulations and radiative transfer modeling to analyze the clustering and evolution of Lyman Alpha Emitters during reionization, constraining key parameters like ionizing photon escape fraction and neutral hydrogen fraction.

Contribution

It introduces a combined simulation and radiative transfer approach to simultaneously constrain reionization parameters and galaxy properties at high redshift.

Findings

Reionization significantly affects the amplitude of LAE angular correlation functions.

Galaxies with stellar mass above 10^{8.5} M_sun can be observed as LBGs or LAEs.

The fraction of time galaxies spend as LBGs or LAEs increases with UV luminosity and stellar mass.

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 $z\simeq6.6$) galaxies spend as Lyman Break Galaxies (LBGs) or as LBGs with Lyman Alpha (Ly$\alpha$) 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$\alpha$ 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.