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P.F. Goldsmith (Cornell U.)
In this talk, I give an overview of the ALFA instrument, a 7 element focal plane array on the Arecibo 305m telescope, which covers the frequency range 1225 to 1525 MHz. Each pixel observes two orthogonal linear polarizations. There are several spectrometers for different types of observations. For Galactic astronomy, a FFT spectrometer has been developed by D. Werthimer and colleagues, which has 8192 channels covering 7 MHz (~1500 km/s at ~0.2 km/s resolution) along with 256 channels covering 100 MHz intended for measuring and removing spectral baselines. ALFA test observations have been underway since August 2004, and astronomical observations should be ramping up through Fall 2004 and be in full swing by early 2005.
The GALFA consortium is comprised of individuals interested in using the ALFA system for galactic astronomy. It is divided by interest into subconsortia, focusing on a number of the outstanding problems which can be addressed by ALFA on the Arecibo telescope, with 8-10 K/Jy gain, ~3.5’ beamwidth, and 30–35 K system temperature. One subconsortium is planning to carry out a survey of 21cm continuum radiation from the Milky Way, focusing on mapping the polarized emission in order to perform Faraday tomography of the magnetic field distribution. Radio recombination lines are the focus of another subconsortium; the ALFA system will be able to observe multiple RRLs that fall within its bandpass. HI emission and absorption will be utilized by a number of consortia, but applied to different problems, including the Galactic plane, high latitude clouds, high velocity clouds, turbulence, and the relationship of the atomic and molecular components of the ISM. Each subconsortium is making plans, starting with relatively small-scale projects, and working towards large-scale projects. Commensal (GALFA together with extragalactic or pulsar observations) are anticipated, using multiple signal processing systems simultaneously.
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Bulletin of the American Astronomical Society, 36 5
© 2004. The American Astronomical Society.