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ALFALFA: HI Cosmology in the Local Universe

Published online by Cambridge University Press:  01 June 2007

Riccardo Giovanelli
Riccardo Giovanelli*
Affiliation:
Center for Radiophysics and Space Research, Cornell University, Ithaca, NY 14853, email: [email protected]
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Abstract

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For the last 25 years, the 21 cm line has been used productively to investigate the large–scale structure of the Universe, its peculiar velocity field and the measurement of cosmic parameters. In February 2005 a blind HI survey that will cover 7074 square degrees of the high latitude sky was started at Arecibo, using the 7-beam feed L-band feed array (ALFA). Known as the Arecibo Legacy Fast ALFA (ALFALFA) Survey, the program is producing a census of HI-bearing objects over a cosmologically significant volume of the local Universe. With respect to previous blind HI surveys, ALFALFA offers an improvement of about one order of magnitude in sensitivity, 4 times the angular resolution, 3 times the spectral resolution, and 1.6 times the total bandwidth of HIPASS. ALFALFA can detect 7×104D2M⊙ of HI, where D is the source distance in Mpc. As of mid 2007, 44% of the survey observations and 15% of the source extraction are completed. We discuss the status of the survey and present a few preliminary results, in particular with reference to the proposed “dark galaxy” VirgoHI21.

Keywords

galaxies: distances and redshiftsgalaxies: dwarfgalaxies: evolutiongalaxies: formationgalaxies: mass functiongalaxies: spiralcosmology: cosmological parameterscosmology: observationscosmology: large-scale structure of universeradio lines: galaxies
Type
Contributed Papers
Information
Proceedings of the International Astronomical Union , Volume 3 , Symposium S244: Dark Galaxies and Lost Baryons , June 2007 , pp. 73 - 82
Copyright
Copyright © International Astronomical Union 2008

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