A Deep Lyα Survey in ECDF-S and COSMOS. I. General Properties of Lyα Emitters at z ∼ 2

Ly alpha emitters (LAEs) may represent an important galaxy population in the low-mass regime. We present our deep narrowband imaging surveys in the COSMOS and ECDF-S fields and study the properties of LAEs at z = 2.23 +/- 0.03. The narrowband surveys conducted at the Magellan II telescope allow us to obtain a sample of 452 LAEs, reaching a 5 sigma limiting magnitude of similar to 26 mag. Our Ly alpha luminosity functions extend to L(Ly alpha) = 10(418) erg s(-1) with a steep faint-end slope. Using multiwavelength ancillary data, especially the deep Spitzer/JRAC 3.6 and 4.5 mu m photometric data, we obtained reliable stellar mass estimates for 130 IRAC-detected LAEs, spanning a range of 8 < log(M-*/M-circle dot) < 11.5. For the remaining IRAC-undetected LAEs, the median-stacked spectral energy distribution yields a stellar mass of log (M-*/M-circle dot) = 7.97(-0.07)(+0.05) and the rest-frame ultraviolet emission indicates a median star formation rate (SFR) of log (SFR/M-circle dot yr(-1)) = 0.14 +/- 0.35. There are six LAEs detected by the Spitzer/MIPS 24 mu m or even Herschel far-infrared observations. Taking into account the six mid-IR/far-IR-detected LAEs, our LAEs cover a wide range in the SFR (1 M-circle dot yr(-1) < SFR < 2000 M-circle dot yr(-1)) Although LAEs as a population are diverse in their stellar properties, they are mostly low-mass star-forming galaxies and follow the star formation main-sequence relations or their extrapolations to the low-mass end, implying a normal star-forming nature of LAEs. The clustering analysis indicates that our LAEs reside in dark matter halos with log (M-h/M-circle dot) = 10.8(-1.1)(+0.56), suggesting that they are progenitors of local LMC-like galaxies.