| Direct observations of the first stars, which are believed to have formed from metal-free gas clouds, are extremely challenging. However, the intergalactic medium (IGM) and circumgalactic medium (CGM) around high-redshift galaxies can provide information about the signatures of chemical enrichment by the first stars or early generations of stars. Using absorption lines in the spectra of high-redshift quasars, one can study the IGM and the CGM of galaxies situated along the sightlines to the quasars. Here we present spectroscopic analysis of a sample of damped/sub-damped Lyman-alpha absorbers (DLA/sub-DLAs) at z > 4.5 based on our observations from Magellan MIKE, complemented with archival VLT data. We measure the abundances for C, O, Si, Fe, and/or Mg, and investigate the metallicity-redshift relation at z > 4.5 (spanning the first ~1 billion years after the Big Bang). We find some cases of metal-poor absorbers that may show signatures of enrichment by early stars, while one case shows very high metallicity and dust depletion. |
