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A. Saintonge, R. Giovanelli, M.P. Haynes, B.R. Kent, S. Stierwalt (Cornell University), N. Brosch (Wise Observatory), B. Catinella, E. Momjian (NAIC)
The Arecibo Legacy Fast ALFA (ALFALFA) Survey is an ongoing project at the Arecibo Observatory. Taking advantage of the new ALFA feed array, 7000 square degrees of high galactic latitude extragalactic sky will be mapped out in L-band in a two pass, fixed Azimuth drift scan mode. The survey is expected to reveal on the order of 20,000 extragalactic HI sources over the 5 years required for its completion. Data are collected at the rate of 1 Gb per hour. Due to the sheer size of the project, a reliable, automated signal detection utility is of the highest importance. A matched-filtering approach has been taken to design the signal extraction algorithm for ALFALFA. By detecting sources based on cross-correlation of signal templates with the data, rather than using a simple peak finding technique, the algorithm is far less vulnerable to spectral baseline instabilities and more sensitive to total, rather than peak flux. This allows for the reliable detection of galaxies with broad signals but low intensity, as well as narrow lines. Both a 2D and a 3D version of the extractor have been written to identify sources out of position-velocity maps as soon as they are obtained and out of the full data cubes when the two passes of the survey have been completed, respectively. The performance of the signal extractor will be presented, based on the results of simulations and on a first generation of ALFALFA data. This research has been partly supported by NSF grants AST--0307661 and AST--0435697, by the Brinson Foundation, and by the Fonds québécois de la recherche sur la nature et les technologies.
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Bulletin of the American Astronomical Society, 37 #4
© 2005. The American Astronomical Soceity.