Simulations of the Lyman Alpha Forest

Gregory Novak, University of California, Santa Cruz

We have added a parallel fixed grid Eulerian hydrodynamics component to an existing particle-mesh N-body code for self-gravitating matter in an expanding universe. The code is being used to simulate intergalactic gas in the distant past (redshift 2-4) with the goal of reproducing the observed properties of the Lyman alpha forest (LAF). We are currently studying the effect of inhomogeneities in the spatial distribution of sources of ultraviolet background light in the early universe on the properties of the LAF. The LAF is a dense set of absorption lines seen in the spectra of distant quasars due to clouds of neutral hydrogen along the line of sight. The detailed structure of the LAF gives information about both the spectrum and the amplitude of density fluctuations in the early universe that gave rise to all present-day structure (Croft et al. 1998, Gnedin and Hamilton 2002).

Croft, Weinberg, Katz and Hernquist, Astrophysical Journal 495:44 (1998).

Gnedin and Hamilton, Monthly Notices of the Royal Astronomical Society, 334:107 (2002).

Abstract Author(s): G. S. Novak and M. White