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T. J. W. Lazio, N. E. Kassim, K. Weiler, C. A. Gross (NRL)
Recent application of self-calibration techniques to low-frequency (< 150~MHz) radio interferometric data have enabled high-resolution, high sensitivity imaging at long wavelengths for the first time. We illustrate these advances using images obtained from the new 74~MHz system on the NRAO Very Large Array. These images have sub-arcminute resolution and sub-Jansky sensitivity.
We then discuss the proposed Low-Frequency Array (LOFAR), a planned completely electronic array largely inspired by the VLA 74~MHz breakthrough. LOFAR is envisaged to be an interferometer operating in the 10--150~MHz frequency range, and possibly as wide as 3--300~MHz. It will have up to a square kilometer of collecting area, milliJansky sensitivity, and arcsecond resolution. LOFAR will surpass, by 2--3 orders of magnitude, the power of previous imaging instruments in its frequency range, and thus effectively open a new window on the electromagnetic spectrum.
LOFAR's science objectives include (1)~Study of planetary and solar radio emission processes; (2)~Constraining the three-dimensional distribution of the Galactic cosmic ray gas and studying Galactic supernova remnants and pulsars; and (3)~Imaging the high-redshift Universe, including high-redshift radio galaxies and galaxy clusters and possibly the first structures to form near the epoch of reionization. LOFAR may also serve as the receiving instrument for imaging bi-static solar radar experiments. Because of LOFAR will open a new window on the spectrum, the possibility of discovering new classes of sources or physical phenomena is also likely.
Basic research in radio astronomy at the Naval Research Laboratory is supported by the Office of Naval Research.
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The author(s) of this abstract have provided an email address for comments about the abstract: lazio@rsd.nrl.navy.mil