2001/08/08 by Sandhya M. Rao, Rao, Sandhya M., David A. Turnshek +1
Physics and Astronomy · #Astrophysics (astro-ph) #Cosmology and Gravitation Theories #FOS: Physical sciences #Galaxies: Formation, Evolution, Phenomena #Scientific Research and Discoveries #astro-ph
paper · pdf · doi:10.48550/arxiv.astro-ph/0108141
10 pages, 4 figures, uses newpasp.sty. To appear in ASP Conference Series, "Extragalactic Gas at Low Redshift", J. Mulchaey and J. Stocke, eds
arxiv created 2001/08/08 · openalex publication_date 2001/08/08 · arxiv updated 2009/12/01 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/28
We discuss our recent results on the statistical properties of damped Lyman alpha systems (DLAs) at low redshift (z<1.65) (Rao & Turnshek 2000). Contrary to expectations, we found that the cosmological neutral gas mass density as traced by DLAs, ΩDLA, does not evolve from redshifts z ≈ 4 to z ≈ 0.5 and that extrapolation to z=0 results in a value that is a factor of ~6.5 times higher than what is derived from galaxies at the current epoch using HI 21 cm emission measurements. We review the current status of HI measurements at low redshift and at the current epoch, and discuss possible causes of this discrepancy.