Clustering of Lyα emitters at z ≈ 4.5

We present the clustering properties of 151 Lyα-emitting galaxies at z ≈ 4.5 selected from the Large Area Lyman Alpha (LALA) survey. Our catalog covers an area of 36′ × 36′ observed with five narrowband filters. We assume that the angular correlation function w(θ) is well represented by a power law A_wθ^-β with slope β-0.8, and we find A_w = 6.73 ± 1.80. We then calculate the correlation length r₀ of the real-space two-point correlation function ξ(r) = (r/r₀)^-1.8 from A_w through the Limber transformation, assuming a flat, Λ-dominated universe. Neglecting contamination, we find r₀ = 3.20 ± 0.42 h ^-1 Mpc. Taking into account a possible 28% contamination by randomly distributed sources, we find r₀ = 4.61 ± 0.6 h^-1 Mpc. We compare these results with the expectations for the clustering of dark matter halos at this redshift in a cold dark matter model, and find that the measured clustering strength can be reproduced if these objects reside in halos with a minimum mass of (1-2) × 10¹¹ h^-1 M _⊙. Our estimated correlation length implies a bias of b ∼ 3.7, similar to that of Lyman break galaxies (LBGs) at z ∼ 3.8-4.9. However, Lyα emitters are a factor of ∼2-16 rarer than LBGs with a similar bias value and implied host halo mass. Therefore, one plausible scenario seems to be that Lyα emitters occupy host halos of roughly the same mass as LBGs, but shine with a relatively low duty cycle of 6%-50%.