Galactic morning: ALMA and the evolution of galaxies

The importance of the Atacama Large Millimeter Array (ALMA) to the study of high-redshift dusty gas-rich galaxies is described. ALMA will have dramatically greater sensitivity and angular resolution than existing millimetre(mm)/submm-wave telescopes. Two key areas are emphasized: i) extremely deep galaxy surveys down to flux densities of about 10-μJy, two orders of magnitude deeper than can be reached using existing telescopes; ii) the study of known high-redshift galaxies, quasars and gravitational lenses. The sensitivity of ALMA will allow very faint galaxies to be detected, while its angular resolving power avoids the problem of source confusion. Dust continuum emission, molecular rotational line emission and atomic fine-structure line emission will all be detected from high-redshift galaxies. Both the spatial structure of continuum emission and the spatial and velocity structure of line emission will be resolved, revealing the astrophysical processes at work in detail. These programs are very complementary to surveys using the Next Generation Space Telescope (NGST) and Planck Surveyor.