A Spectroscopic Survey of Lyα Emitters at z ≈  3.1 over ∼1.2 Deg²

We present a spectroscopic survey of Lyα emitters (LAEs) at z ≈ 3.1 in the Subaru XMM-Newton Deep Survey Field. This field has deep imaging data in a series of broad and narrow bands, including two adjacent narrow bands NB497 and NB503 that have allowed us to efficiently select LAE candidates at z ≈ 3.1. Using spectroscopic observations on MMT Hectospec and Magellan M2FS, we obtained a sample of 166 LAEs at z ≈ 3.1 over an effective area of ∼1.2 deg², including 16 previously known LAEs. This is so far the largest (spectroscopically confirmed) sample of LAEs at this redshift. We make use of the secure redshifts and multiband data to measure spectral properties such as Lyα luminosity and rest-frame UV slope. We derive a robust Lyα luminosity function (LF) that spans a luminosity range from ∼10^42.0 to >10^43.5 erg s⁻¹. Significant overdense and underdense regions are detected in our sample, but the area coverage is wide enough to largely suppress the effect from such cosmic variance. Our Lyα LF is generally consistent with those from previous studies at z ∼ 3.1. At the brightest end of the LF, there is a tentative detection of a density excess that is not well described by the Schechter function. The comparison with the LFs at other redshifts suggests that the Lyα LF does not show significant evolution at 2 < z < 5. Finally, we build the composite spectra of the LAEs and detect the N v λ1239 and C iv λλ1548,1551 doublet emission lines at significance of ∼4σ, suggesting very hard radiation fields in (some of) these LAEs.