The Low Redshift Lyman Alpha Forest in Cold Dark Matter Cosmologies

Details The Low Redshift Lyman Alpha Forest in Cold Dark Matter Cosmologies The Low Redshift Lyman Alpha Forest in Cold Dark Matter Cosmologies

1998-07-16

arxiv.org/abs/astro-ph/9807177v1

Astrophys.J.511:521-545,1999

Astronomy and Astrophysics

Astrophysics

57 pages, 18 figures, submitted to ApJ

Scientific paper

10.1086/306722

We study the physical origin of the low-redshift Lyman alpha forest in hydrodynamic simulations of four CDM cosmologies. Our main conclusions are insensitive to the cosmological model but depend on our assumption that the UV background declines at low redshift. We find that the expansion of the universe drives rapid evolution of dN/dz (the number of absorbers per unit z) at z > 1.7, but that at lower redshift the fading of the UV background counters the influence of expansion, leading to slow evolution. At every redshift, weaker lines come primarily from moderate fluctuations of the diffuse, unshocked IGM, and stronger lines originate in shocked or radiatively cooled gas of higher overdensity. However, the neutral hydrogen column density associated with structures of fixed overdensity drops as the universe expands, so an absorber at z = 0 is dynamically analogous to an absorber with neutral hydrogen column density 10 to 50 times higher at z = 2-3. We find no clear distinction between lines arising in "galaxy halos" and lines arising in larger scale structures; however, galaxies tend to lie near the dense regions of the IGM that produce strong Lyman alpha lines. The simulations provide a unified physical picture that accounts for the most distinctive observed properties of the low redshift Lyman alpha forest: (1) a sharp transition in the evolution of dN/dz at z ~ 1.7, (2) stronger evolution for absorbers of higher equivalent width, (3) a correlation of increasing Lyman alpha equivalent width with decreasing galaxy impact parameter, and (4) a tendency for stronger lines to arise in close proximity to galaxies while weaker lines trace more diffuse large scale structure. (Abridged)

Affiliated with

Also associated with

No associations

Rating

The Low Redshift Lyman Alpha Forest in Cold Dark Matter Cosmologies does not yet have a rating. At this time, there are no reviews or comments for this scientific paper.

If you have personal experience with The Low Redshift Lyman Alpha Forest in Cold Dark Matter Cosmologies, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and The Low Redshift Lyman Alpha Forest in Cold Dark Matter Cosmologies will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFWR-SCP-O-83270