Research Objectives:
For decades the study of the first collapsed objects has largely been a theoretical exercise since almost no data from redshift higher than five were available. The high redshift universe, where the first ionizing objects resided, was inaccessable to observation. That changed suddenly in February 2003. Using the WMAP (Wilkinson Microwave Anisotropy Probe) satellite, investigators reported evidence that the universe was ionized bery early, before age 200 million years. To ionize the universe at the then-prevailing hydrogen density would have required a very strong UV (ultraviolet) flux and that means it is likely that the first UV-effusive objects were formed much earlier than many cosmologists had thought. The early ionization means the universe was more violent, structured and interesting in its youth than many had considered.
This project will build and test the PrimevAl Structure Telescope (PAST) and use it to locate and study the era of formation of the earliest luminous objects. The primeval structures researchers expect to find contained the first stars, supernova explosions, and/or black holes. All these objects were strong sources of UV radiation so they ionized the material surrounding them. It is this ionization the PAST instrument will detect and study. The structure of this ionization reflects the overall density structure at the redshift of luminous-object formation.
The PAST will be a sparse array of 1,000 antennae spanning several square kilometers of ice surface adjacent to the station. The instrument will be build almost entirely of inexpensive commercially available components. The design will closely follow that of the proven South Pole Riometer, a VHF interferometer array which has been operating efficiently for a decade (Rosenberg, now Weatherwax, A-111-M/S).
The PAST array will image and spectrally resolve hyperfine emission of neutral hydrogen at redshifts from 6 to 35. As the primeval energy release developed, bubbles of ionization temporarily eliminated this emission. These bubbles were essentially the aggregate Stromgren spheres of protogalaxy groups and clusters. The PAST instrument will image these bubbles in three dimensions, allowing researchers to study their evolution and their merging. Scientists hope to understand the timing of formation of the first bright objects.
In addition to enabling study of the ancient history of the universe, the PAST array will provide polarized images of the galaxy with unprecedented resolution. PAST will also continuously image ionospheric absorption in finer detail than ever before.
