Ionized Gas in high-redshift galaxy halos . ... An alternative way to detect such galaxies is to analyze the spectra of luminous background objects (quasars and gamma-ray bursts), and look for the tell-tale absorption lines that arise due to foreground galaxies lying along the line-of-sight. ... Aside from their interest as the endpoints of massive star evolution, GRBs are ideal background sources for absorption-line spectroscopy, thanks to their enormous luminosities and smooth power-law continua. ...