[JEK2011] 12 , the SIMBAD biblio

We present Keck spectroscopic observations of z > 6 Lyman-break galaxy (LBG) candidates in the Subaru Deep Field (SDF). The candidates were selected as i'-dropout objects down to z' = 27 AB magnitudes from an ultra-deep SDF z'-band image. With the Keck spectroscopy we identified 19 LBGs with prominent Lyα emission lines at 6 ≤ z ≤ 6.4. The median value of the Lyα rest-frame equivalent widths (EWs) is ∼50 Å, with four EWs >100 Å. This well-defined spectroscopic sample spans a UV-continuum luminosity range of -21.8 ≤ M_UV ≤ -19.5 (0.6 ∼ 5 L*_UV) and a Lyα luminosity range of (0.3-3) x10⁴³ erg/s (0.3-3 L*_Lyα). We derive the UV and Lyα luminosity functions (LFs) from our sample at ∼ 6.2 after we correct for sample incompleteness. We find that our measurement of the UV LF is consistent with the results of previous studies based on photometric LBG samples at 5 < z < 7. Our Lyα LF is also generally in agreement with the results of Lyα-emitter surveys at z ∼ 5.7 and 6.6. This study shows that deep spectroscopic observations of LBGs can provide unique constraints on both the UV and Lyα LFs at z > 6.