| Abstract : | Lyman-α forest data are known to be a good probe of the small scale matter power. In this paper, we explore the redshift evolution of the observable effective optical depth τeff(z) from the Lyman-α data as a discriminator between dark matter models that differ from the ΛCDM model on small scales. Considering the thermal warm dark matter (WDM) and the ultra-light axion (ULA) models with the following set of parameters: the mass of ULA, m_a \sim 10^{-24} - 5×10{−22} eV and WDM mass, m_{\rm wdm}= 0.1 - 4.6 keV. We simulate the line-of-sight HI density and velocity fields using semi-analytic methods. The simulated effective optical depth for the alternative dark matter models diverges from the ΛCDM model for z≳3, which provides a meaningful probe of the matter power at small scales. Using likelihood analysis, we compare the simulated data with the high-resolution Lyman-α forest data in the redshift range 2 < z < 4.2. The analysis yields the following 1σ bounds on dark matter masses: m{\rm wdm} > 0.7 keV and m_a > 2 \times 10^{-23} eV. To further test the efficacy of our proposed method, we simulate synthetic data sets compatible with the ΛCDM model in the redshift range 2 \leq z \leq 6.5 and compare with theory. The 1σ bounds obtained are significantly tighter: m{\rm wdm} > 1.5 keV and m_a > 7 \times 10^{-23} eV. Although our method demonstrates an alternative approach for constraining dark matter models, we note that these bounds are weaker than those obtained by high-resolution hydrodynamical simulations. |
