Clustering of Lyα emitters at z ≈ 4.5

We present the clustering properties of 151 Ly alpha-emitting galaxies at z approximate to 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(theta) is well represented by a power law Aw theta(-beta) with slope beta = 0.8, and we find A(w) = 6.73 +/- 1.80. We then calculate the correlation length r(0) of the real- space two- point correlation function xi(r) (r/r(0))(-1.8) from A(w) through the Limber transformation, assuming a flat, Lambda-dominated universe. Neglecting contamination, we find r(0) 3.20 +/- 0.42 h(-1) Mpc. Taking into account a possible 28% contamination by randomly distributed sources, we find r(0) = 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); 10(11) h(-1) M-circle dot. Our estimated correlation length implies a bias of b similar to 3.7, similar to that of Lyman break galaxies (LBGs) at z similar to 3.8-4.9. However, Ly alpha emitters are a factor of similar to 2-16 rarer than LBGs with a similar bias value and implied host halo mass. Therefore, one plausible scenario seems to be that Ly alpha emitters occupy host halos of roughly the same mass as LBGs, but shine with a relatively low duty cycle of 6%-50%.