A Magellan M2FS Spectroscopic Survey of Galaxies at 5.5 < z < 6.8: Program Overview and a Sample of the Brightest Lyα Emitters

We present a spectroscopic survey of high-redshift, luminous galaxies over four square degrees on the sky, aiming to build a large and homogeneous sample of Lyα emitters (LAEs) at and 6.5, and Lyman-break galaxies (LBGs) at . The fields that we choose to observe are well studied, such as by the Subaru XMM-Newton Deep Survey and COSMOS. They have deep optical imaging data in a series of broad and narrow bands, allowing for the efficient selection of galaxy candidates. Spectroscopic observations are being carried out using the multi-object spectrograph M2FS on the Magellan Clay telescope. M2FS is efficient enough to identify high-redshift galaxies, owing to its 256 optical fibers deployed over a circular field of view in diameter. We have observed ∼2.5 square degrees. When the program is completed, we expect to identify more than 400 bright LAEs at and 6.5, and a substantial number of LBGs at . This unique sample will be used to study a variety of galaxy properties and to search for large protoclusters. Furthermore, the statistical properties of these galaxies will be used to probe cosmic reionization. We describe the motivation, program design, target selection, and M2FS observations. We also outline our science goals, and present a sample of the brightest LAEs at and 6.5. This sample contains 32 LAEs with Lyα luminosities higher than 10⁴³ erg s^-1. A few of them reach ≥3 10⁴³ erg s^-1, comparable to the two most luminous LAEs known at , "CR7" and "COLA1." These LAEs provide ideal targets to study extreme galaxies in the distant universe.