The Magellan M2FS Spectroscopic Survey of High-redshift Galaxies: A Sample of 260 Lyα Emitters at Redshift z ≈ 5.7

We present a spectroscopic survey of Ly α emitters (LAEs) at z ≈ 5.7 using the multiobject spectrograph M2FS on the Magellan Clay telescope. This is part of a high-redshift galaxy survey carried out in several well-studied deep fields. These fields have deep images in multiple UV/optical bands, including a narrow NB816 band that has allowed an efficient selection of LAE candidates at z ≈ 5.7. Our sample consists of 260 LAEs and covers a total effective area of more than 2 deg 2 on the sky. This is so far the largest (spectroscopically confirmed) sample of LAEs at this redshift. We use the secure redshifts and narrowband photometry to measure Ly α luminosities. We find that these LAEs span a Ly α luminosity range of erg s −1 and include some of the most luminous galaxies known at in terms of Ly α luminosity. Most of them have rest-frame equivalent widths between 20 and 300 Å, and more luminous Ly α emission lines tend to have broader line widths. We detect a clear offset of ∼20 Å between the observed Ly α wavelength distribution and the NB816 filter transmission curve, which can be explained by the intergalactic medium absorption of continua blueward of Ly α in the high-redshift spectra. This sample is being used to study the Ly α luminosity function and galaxy properties at z ≈ 5.7.