VLA EoR PROGRAM

Scientific Background

The Universe began at the Big Bang, with the birth of a hot soup of radiation and matter. The soup cooled, and eventually the matter separated out -- electrons and protons recombined to make neutral Hydrogen (HI). Thus began theCosmological Dark Ages,about 300,000 years after the Big Bang. There were no stars, no quasars, no luminous sources. The universe was dark.

Over time, self-gravity fragmented the matterand condensations collapsed to form the "first" stars, black holes, and quasars. Numbers grew, and over time, these luminous objects reionized the universe, leaving behind a largely transparent universe dotted with quasars and clusters of galaxies.

There is little data to tell us what the universe looked like during Reionization and when the earliest compact objects (e.g., stars) formed.

The best way to understand the Dark Ages is to map directly the distribution of Hydrogen -- the dominant visible component of the early universe.

Astronomers at the Smithsonian Astrophysical Observatory, Harvard University, and National Radio Astronomy Observatory are working to outfit the Very Large Array in New Mexico for detection of HI emission at high redshift. The predicted spectral-line signal is on the order of 20 mK at frequencies below 200 MHz, or wavelengths longer than 1.5 meters (z~6.2).

Each VLA antenna will be equipped with a crossed dipole feed positioned just below the sub-reflector, in an arrangement similar to what is used for the existing 320 MHz system.Receivers will be placed in the cabins behind the sub-reflectors.The “2-band” observing system has been designed for high sensitivity (Stokes I), low operational overhead, and minimum impact on the community and the EVLA upgrade.

The Smithsonian Astrophysical Observatory is providing hardware and engineering services. Field testing of prototypes began on March 9, 2005. Testing of final designs began on November 9, 2005. A final review by NRAO will follow these test programs. If approved, deployment will proceed apace. The goal is to complete deployment in time for demonstration of capability in 2006 and acquisition of science data during the 2007 D-configuration. Array time has already been recommended by peer review, contingent on performance.

Science case proposed to NRAO - Extracted from the technical & management doc. 01/05 (pdf)
                                                               Proposal AG706 - 06/05 (pdf)