High-redshift Lyman-α galaxies

A strong Lyman-α line enables relatively easy detection of high redshift galaxies. Lyman-α galaxies are now known from z = 3 to 6.6. No evolution is discerned in the Lyman-α line luminosity function in this redshift range. This implies that the intergalactic medium at z = 6 is at least 50% ionized over more than 50% of the volume. Recent continuum detections of these galaxies from HST, MMT and Spitzer are now allowing us to address questions about the nature of these Lyman-α emitters, their stellar populations and ages. We find that by and large the Lyman-α galaxies are young galaxies dominated by stellar populations that are less than 25 Myr old.