Star Formation At High Redshift

摘要

I review the observational characteristics of intermediate-to-high redshift star forming galaxies, including their star formation rates, dust extinctions, ISM kinematics, and their chemical compositions. I present evidence that the mean rate of metal enrichment, Z/z, from z = 0 – 3, as determined from nebular oxygen abundance measurements in star forming galaxies, is 0.15 dex per redshift unit for galaxies more luminous than MB = –20.5. This rate of chemical enrichment is consistent with the chemical rise in Galactic disk stars. It is less dramatic than, but perhaps consistent with the rate of 0.18 – 0.26 ± 0.07 dex per redshift unit seen in Damped Ly systems, and much less than predicted by many cosmological evolution models. The high-redshift galaxies observed to date are the most luminous examples from those epochs, and thus trace only the greatest cosmological overdensities. Star formation in the first 1 – 2 Gyr appears sufficient to elevate ambient metallicities to near or above the solar value, implying efficient retention of metals in these densest environments.