The Abundance of Low‐Luminosity Lyα Emitters at High Redshift

Abstract

We derive the luminosity function of high-redshift Ly{α}-emittingsources from a deep, blind, spectroscopic survey that utilizedstrong-lensing magnification by intermediate-redshift clusters ofgalaxies. We observed carefully selected regions near nine clusters,consistent with magnification factors generally greater than 10 for theredshift range 4.5{\lt}z{\lt}6.7. Eleven emission-line candidates werelocated in the range 2.2{\lt}z{\lt}5.6 whose identification we justify asLy{α}, in most cases via further spectroscopic observations. Theselection function we constructed for our survey takes into account ourvarying intrinsic Ly{α} line sensitivity as a function of wavelengthand sky position. By virtue of the strong magnification factor, weprovide constraints on the Ly{α} luminosity function tounprecedented limits of 10^{40} ergs s^{ -1},corresponding to a star formation rate of 0.01 M_{solar}yr^{-1}. Our cumulative z~=5 Ly{α} luminosity function isconsistent with a power-law form n({\gt}L)~L^{-1} over10^{41}-10^{42.5} ergs s^{-1}. When combinedwith the results of other surveys, limited at higher luminosities, ourresults suggest evidence for the suppression of star formation inlow-mass halos, as predicted in popular models of galaxy formation.Data presented herein were obtained at the W. M. Keck Observatory, whichis operated as a scientific partnership among the California Instituteof Technology, the University of California, and the NationalAeronautics and Space Administration. The Observatory was made possibleby the generous financial support of the W. M. Keck Foundation.