Narrow-band searches for Lyman- \alpha emission are an efficient way of identifying star-forming galaxies at high redshifts .
We present Keck telescope spectra confirming redshifts z \approx 5.7 for three objects discovered in the Large Area Lyman Alpha ( LALA ) survey at Kitt Peak National Observatory .
All three spectra show strong , narrow emission lines with the asymmetric profile that is characteristically produced in high redshift Lyman- \alpha emitters by preferential HI absorption in the blue wing of the line .
These objects are undetected in deep B _ { W } , V , R , and \lambda \approx 6600 Å narrow-band images from the NOAO Deep Wide-Field Survey and from LALA , as expected from Lyman break and Lyman- \alpha forest absorption at redshift z \approx 5.7 .
All three objects show large equivalent widths ( \gtrsim 150 Å in the rest-frame ) , suggesting at least one of the following : a top-heavy initial mass function , very low stellar metallicity , or the presence of an active nucleus .
We consider the case for an active nucleus to be weak in all three objects due to the limited width of the Lyman- \alpha emission line ( < 500 \hbox { km s$ { } ^ { -1 } $ } ) and the absence of any other indicator of quasar activity .
The three confirmed high redshift objects were among four spectroscopically observed targets drawn from the sample of 18 candidates presented by Rhoads & Malhotra ( 2001 ) .
Thus , these spectra support the Lyman- \alpha emitter population statistics from our earlier photometric study , which imply little evolution in number density from z = 5.7 to z = 4.5 and provide strong evidence that the reionization redshift z _ { r } > 5.7 .