A Magellan M2FS Spectroscopic Survey of Galaxies at 5.5<z<6.8: Program
  Overview and a Sample of the Brightest Lyman-alpha 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 Ly$\alpha$ emitters (LAEs) at $z\approx5.7$ and 6.5, and Lyman-break
galaxies (LBGs) at $5.5<z<6.8$. The fields that we choose to observe are
well-studied, such as SXDS and COSMOS. They have deep optical imaging data in a
series of broad and narrow bands, allowing 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 to identify high-redshift galaxies, owing to its 256 optical fibers
deployed over a circular field-of-view 30 arcmin in diameter. We have observed
$\sim2.5$ square degrees. When the program is completed, we expect to identify
more than 400 bright LAEs at $z\approx5.7$ and 6.5, and a substantial number of
LBGs at $z\ge6$. 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 $z\approx5.7$ and 6.5. This sample contains 32 LAEs with
Ly$\alpha$ luminosities higher than 10$^{43}$ erg s$^{-1}$. A few of them reach
$\ge3\times10^{43}$ erg s$^{-1}$, comparable to the two most luminous LAEs
known at $z\ge6$, `CR7' and `COLA1'. These LAEs provide ideal targets to study
extreme galaxies in the distant universe.
