Star and galaxy formation waxed and waned over the history of the Universe. Submillimeter cameras revealed an apparent peak of massive galaxy formation at redshift z between 2 and 3 (3.3 to 2.2 Gyr after the Big Bang). These early luminous galaxies contain so much dust that they are extremely faint or invisible at observe-frame optical wavelengths. Finding their redshifts and exploring their dynamical states often requires observations of spectral lines at submillimeter and longer wavelengths. Multi-line observations of molecular transitions are necessary to understand the state of the molecular gas that fuels star formation.
A number of new broadband instruments have been built to search for long-wavelength lines from these distant galaxies and establish their redshifts. After reviewing the scientific puzzles the instruments address, I will discuss the science targets and related technology of one of these "redshift machines," the Zpectrometer, a collaborative project between the University of Maryland, Rutgers, and the National Radio Astronomy Observatory. The Zpectrometer targets the ground-state carbon monoxide J=1-0 line from z of about 2 to 3.5; this line is redshifted into centimeter wavelengths and can be observed with the 100 meter Green Bank telescope. Detecting this line traces cold molecular gas that formed just Gyr after the Big Bang and provides a bridge to observations with millimeter-wave interferometers.
Received December 6, 2007