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

TL;DR

This paper details a spectroscopic survey of high-redshift galaxies using M2FS, aiming to identify and analyze luminous Lyα emitters and Lyman-break galaxies at z≈5.5–6.8 to understand galaxy evolution and cosmic reionization.

Contribution

It introduces a large, homogeneous sample of high-redshift galaxies selected with deep imaging and spectroscopically confirmed using M2FS, including the brightest known LAEs at z≥6.

Findings

Sample of 32 bright LAEs at z≈5.7 and 6.5 identified.

Detection of extremely luminous LAEs comparable to known luminous sources.

Survey will provide data to study galaxy properties and cosmic reionization.

Abstract

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.