[64.01] The Low Frequency Array (LOFAR): Opening a New Window on the Universe

AAS 200th meeting, Albuquerque, NM, June 2002
Session 64. New Developments in Ground Based Instrumentation
Display, Wednesday, June 5, 2002, 10:00am-7:00pm, SW Exhibit Hall

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[64.01] The Low Frequency Array (LOFAR): Opening a New Window on the Universe

T. J. W. Lazio, N. E. Kassim (NRL), W. C. Erickson (U. MD), B. C. Hicks, P. C. Crane, K. P. Stewart, P. S. Ray, K. W. Weiler, L. J Rickard (NRL)

Application of self-calibration techniques to low-frequency (< 150~MHz) radio interferometric data has enabled high-resolution, high sensitivity imaging at long wavelengths for the first time. We illustrate these advances using NRAO Very Large Array 74~MHz images having sub-arcminute resolution and sub-Jansky sensitivity.

The VLA 74~MHz breakthrough has inspired the Low Frequency Array (LOFAR), a completely electronic array planned to operate in the 10--250~MHz frequency range. It will have a square kilometer (10⁶~m{}²) of collecting area at~15~MHz, milliJansky sensitivity, and arcsecond resolution. LOFAR will surpass, by 2--3 orders of magnitude, the power of previous interferometers in its frequency range, and thus open a new window on the electromagnetic spectrum.

We present recent results from the design-and-development phase of LOFAR, including VLA-Pie Town link images and the testing of active dipoles. The 50~km baseline of the VLA-PT link marks the highest resolution imaging ever performed at these frequencies. Our work on active dipoles is being used to explore whether these have the frequency dynamic range required to cover the low (10--90~MHz) band of LOFAR.

LOFAR's scientific objectives include (1)~Planetary and solar radio emission; (2)~The three-dimensional distribution of Galactic cosmic rays and Galactic supernova remnants and pulsars; and (3)~The extragalactic universe, including high-redshift radio galaxies, 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 LOFAR will open a new window on the spectrum, 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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