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C.A. Gross, T.E. Clarke, T.J.W. Lazio, N.E. Kassim, E.J. Polisensky, A.S. Cohen, W.M. Lane (Naval Research Lab)
The Long Wavelength Array (LWA) will be a powerful new instrument that will open a new window of high resolution and sensitivity on the poorly explored region between 20 and 80 MHz. We will describe how the LWA will be an excellent instrument for studying clusters of galaxies and addressing key questions in Cosmology. The assembly of large-scale structures in the Universe is thought to proceed in a hierarchical manner, with smaller structures merging to form larger structures. At least a fraction of the most energetic mergers in the present-day Universe are marked by cluster halos and relics, which are characterized by diffuse, steep-spectrum radio emission not associated with any galaxy in the merging cluster. The current census of cluster halos and relics is considered incomplete due to the low sensitivity of existing long-wavelength instruments. The LWA will have sufficient sensitivity at long wavelengths to detect less energetic and more distant mergers, and it is estimated that there may be thousands of them. When compared with X-ray observations, a complete census of diffuse emission in merging clusters can be used to trace the formation of structure, measure the input of energy into the intracluster medium, and constrain the dark matter potentials that govern mergers. Additionally, the census would define a non-merging cluster sample which would provide the undisturbed systems necessary to study the dark energy equation of state through determination of the baryonic mass fraction in massive clusters.
Basic research in radio astronomy at the Naval Research Laboratory is supported by the Office of Naval Research.
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Bulletin of the American Astronomical Society, 37 #4
© 2005. The American Astronomical Soceity.