HI column density distribution function at z=0: Connection to damped Ly alpha statistics

Martin Zwaan, MAW Verheijen, FH Briggs

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18 Citaten (Scopus)


We present a measurement of the HI column density distribution function f(N-HI) at the present epoch for column densities > 10(20) cm(-2). These high column densities compare to those measured in damped Ly alpha lines seen in absorption against background quasars. Although observationally rare, it appears that the bulk of the neutral gas in the Universe is associated with these damped Ly alpha systems. In order to obtain a good anchor point at z = 0 we determine f(N-HI) in the local Universe by using 21 cm synthesis observations of a complete sample of spiral galaxies. We show that f(N-HI) for damped Ly alpha systems has changed significantly from high z to the present and that change is greatest for the highest column densities. The measurements indicate that low surface brightness galaxies make a minor contribution to the cross section for HI, especially for N-HI > 10(21) cm(-2).

Originele taal-2English
TitelH I Column Density Distribution Function at z =0: Connection to Damped Ly α Statistics
UitgeverijPublications of the Astronomical Society of Australia
Aantal pagina's6
Volume16, issue 1
StatusPublished - apr-1999
EvenementWorkshop on HI in the Local Universe II - , Australia
Duur: 28-sep-199830-sep-1998


OtherWorkshop on HI in the Local Universe II

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