Lyα-EMITTING GALAXIES AT z = 3.1: L~* PROGENITORS EXPERIENCING RAPID STAR FORMATION

摘要

We studied the clustering properties and multiwavelength spectral energy distributions of a complete sample of 162 Lyα-emitting (LAE) galaxies at z (approx=) 3.1 discovered in deep narrowband MUSYC imaging of the Extended Chandra Deep Field-South. LAEs were selected to have observed frame equivalent widths ＞ 80 A and emission line fluxes ＞ 1.5 × 10~(-17) ergs cm~(-2) s~(-1). Only 1% of our LAE sample appears to host AGNs. The LAEs exhibit a moderate spatial correlation length of r_0 = 3.6_(-1.0)~(+0.8) Mpc, corresponding to a bias factor b = 1.7_(-0.4)~(+0.3), which implies median dark matter halo masses of log_(10)M_(med) = 10.9_(-0.9)~(+0.5) M_☉. Comparing the number density of LAEs, 1.5 ± 0.3 × 10~(-3) Mpc~(-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 × 10~9 M_☉) 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_(-0.4)~(+0.6) × 10~9 M_☉), moderate star formation rate (2 ± 1 M_☉ yr~(-1)), a young component age of 20_(-10)~(+30) Myr, and little dust (A_V ＜ 0.2). The best-fit model has 20% of the mass in the young stellar component, but models without evolved stars are also allowed.