TITLE:
Study of Warm Dark Matter with the Lyman-α Forest (Part II)
AUTHORS:
Bruce Hoeneisen
KEYWORDS:
Lyman-Alpha Forest, Warm Dark Matter, Free Streaming, Dark Matter
JOURNAL NAME:
International Journal of Astronomy and Astrophysics,
Vol.16 No.4,
October
29,
2026
ABSTRACT: Observed quasar light as a function of wavelength shows absorptions due to neutral hydrogen “clouds” along the line-of-sight. This “Lyman-
α
forest” has a power spectrum that has a cut-off. We study this cut-off. This cut-off may be due to warm dark matter free-streaming in the early universe, or to neutral hydrogen thermal velocity Doppler shift, or both. It is difficult to distinguish between these alternatives. If warm dark matter free-streaming dominates, we obtain the following density power spectrum cut-off wavevector:
k
fs
=5.7±0.3±2.0
Mpc−1. This is a measure of the dark matter “warmness”. This result is in agreement with four independent published measurements, and in disagreement with published limits.