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R. Giovanelli, M.P. Haynes, K. Spekkens, C.M. Springob, K.L. Masters, A. Saintonge, B. Catinella, B. Kent (Cornell U.), R.J. Maddalena (NRAO), L. Magnani (U. Georgia), R.A. Koopmann (Union College and Cornell U.)
The currently popular \LambdaCDM framework of evolution of cosmic structure predicts a population of low mass halos that far exceeds that of dwarf galaxies. Low mass halos could, however, have retained little of their initial baryonic mass fraction, and their star formation efficiency could be very low. The possibility of detecting such systems in the 21 cm HI line has been investigated by several teams, and blind extragalactic HI surveys have been undertaken to date, pushing estimates of the HI Mass Function to limits approaching 107 M\odot (Zwaan et al. 1997, Rosenberg and Schneider 2002, Zwaan et al. 2003). Extrapolations of those estimates to 106 M\odot disagree with each other quite substantially. Since these low mass objects may represent the population of low mass halos predicted to exist by numerical \LambdaCDM simulations, the determination of their space density and its possible dependence on galaxy environment remains an important goal. Systems of very low HI mass can only be detected at relatively small distances. It thus becomes important to optimize the survey design, matching it to the local characteristics of the cosmic density field. We present results of various survey simulations, some currently underway with the single-beam Arecibo and Green Bank telescopes and future ones that will be enabled with the advent of the Arecibo L-band feed array in late 2004. This work is partially funded by NSF grant AST-0307661.
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Bulletin of the American Astronomical Society, 35#5
© 2003. The American Astronomical Soceity.