Lyα-emitting Galaxies at Z = 3.1: L * Progenitors Experiencing Rapid Star Formation

We studied the clustering properties and multiwavelength spectral energy distributions of a complete sample of 162 Lyα-emitting (LAE) galaxies at z ≃ 3.1 discovered in deep narrow-band MUSYC imaging of the Extended Chandra Deep Field South. LAEs were selected to have observed frame equivalent widths >80Å and emission line fluxes > 1.5× 10−17ergs cm−2 s−1. Only 1% of our LAE sample appears to host AGN. The LAEs exhibit a moderate spatial correlation length of r0 = 3.6+0.8 −1.0Mpc, corresponding to a bias factor b = 1.7 +0.3 −0.4, which implies median dark matter halo masses of log10 Mmed = 10.9 +0.5 −0.9M⊙. Comparing the number density of LAEs, 1.5±0.3×10−3Mpc−3, with the number density of these halos finds a mean halo occupation ∼1–10%. The evolution of galaxy bias with redshift implies that most z = 3.1 LAEs evolve into present-day galaxies with L < 2.5L, whereas other z > 3 galaxy populations typically evolve into more massive galaxies. Halo merger trees show that z = 0 descendants occupy halos with a wide range of masses, with a median descendant mass close to that of L. Only 30% of LAEs have sufficient stellar mass (>∼ 3× 10M⊙) to yield detections in deep Spitzer-IRAC imaging. A two-population SED fit to the stacked UBVRIzJK+[3.6,4.5,5.6,8.0]μm fluxes of the IRAC-undetected objects finds that the typical LAE has low stellar mass (1.0+0.6 −0.4 × 10M⊙), moderate star formation rate (2±1M⊙yr), a young component age of 20+30 −10Myr, and little dust (AV < 0.2). The best fit model has 20% of the mass in the young stellar component, but models without evolved stars are also allowed. Subject headings: galaxies:high-redshift galaxies:formation galaxies:evolution large-scale structure of universe