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 alpha 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 alpha luminosities. We find that these LAEs span a Ly alpha luminosity range of alpha luminosity. Most of them have rest-frame equivalent widths between 20 and 300 A, and more luminous Ly alpha emission lines tend to have broader line widths. We detect a clear offset of similar to 20 A between the observed Ly alpha wavelength distribution and the NB816 filter transmission curve, which can be explained by the intergalactic medium absorption of continua blueward of Ly alpha in the high-redshift spectra. This sample is being used to study the Ly alpha luminosity function and galaxy properties at z approximate to 5.7.