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[79.03] The HI Environment of nearby Ly-\alpha absorbers

M.A. Zamojski, J.H. van Gorkom, S. Giovanardi (Columbia University), J.E. Hibbard (NRAO, Charlottesville), J.T. Stocke (University of Colorado)

We present HI observations of the environment of nine nearby Ly-\alpha absorbers. The goal was to probe regions of space around absorbers to look for HI emission (of any kind) in order to understand better their relation to the large-scale structure of the nearby Universe (< 7000 km s^-1). We probed volumes ranging from 1.0^o X 1.0^o X 600 km s^-1 to 1.5^o X 1.5^o X 1300 km s^-1 around every absorber with detection limits going from M_HI = 5 X 10⁷ M_\odot in the best cases to M_HI = 2 X 10⁸ M_\odot in the worst. In terms of column densities, we can go down to N_HI=3 X 10¹⁹ cm^-2 in some cases. In total, we detect five HI emitters, all galaxies, with four of them actually being in the environment of a common absorber. Among the five galaxies that we detect, three are uncataloged. We also combine these results with previous investigations of six other Ly-\alpha absorbing systems to address such questions as: What is our detection rate of HI compared to unbiased HI surveys? Does detected HI mass correlate with the equivalent width of the Ly-\alpha absorption line? How does the large-scale environment affect HI detection? How do observations compare with simulations?

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Bulletin of the American Astronomical Society, 34, #4
© 2002. The American Astronomical Soceity.