The ALMA View of High-Redshift Galaxy Formation

The advent of routine operations with the Atacama Large Millimeter/submillimeter Array (ALMA) in the past decade has led to a revolution in the direct study of the interstellar medium (ISM) in “normal” high-redshift galaxies in the rest-frame far-infrared (FIR). This review summarizes the observational literature on z > 6.5 sources observed with ALMA and NOEMA (NOrthern Extended Millimeter Array). The main findings are as follows: ▪ Cool gas consistently scales with star formation in a wide range of galaxy environments, similar to local relations, suggesting that fundamental processes of star formation have stayed relatively constant over 13 billion years of cosmic time. ▪ Significant metal enrichment is present in galaxies just ∼300–400 million years after the Big Bang. ▪ There is a trend to a higher obscured fraction of star formation with stellar mass and star-formation rate (SFR) already in place at z $\simeq$ 7, with measurements of the cosmic SFR density showing that >10% of the SFR density is obscured at this epoch. ▪ The estimated dust masses compared to the stellar mass suggest that rapid dust enrichment occurs, likely from supernovae with little dust destruction and/or rapid growth in the ISM, which is in agreement maximal predictions from models. ▪ In individual sources, cold disks are already in existence, with their gas disks being more extended and smoother than their observed stellar counterparts.