The non-linear power spectrum of the Lyman alpha forest

Abstract

Abstract. The Lyman alpha forest power spectrum has been measured on large scales by the BOSS survey in SDSS-III at z ∼ 2.3, has been shown to agree well with linear theory predictions, and has provided the first measurement of Baryon Acoustic Oscillations at this redshift. However, the power at small scales, affected by non-linearities, has not been well examined so far. We present results from a variety of hydrodynamic simulations to predict the redshift space non-linear power spectrum of the Lyα transmission for several models, testing the dependence on resolution and box size. A new fitting formula is introduced to facilitate the comparison of our simulation results with observations and other simulations. The non-linear power spectrum has a generic shape determined by a transition scale from linear to non-linear anisotropy, and a Jeans scale below which the power drops rapidly. In addition, we predict the two linear bias factors of the Lyα forest and provide a better physical interpretation of their values and redshift evolution. The dependence of these bias factors and the non-linear power on the amplitude and slope of the primordial fluctuations power spectrum, the temperature-density relation of the intergalactic medium, and the mean Lyα transmission, as well as the redshift evolution, is investigated and discussed in detail. A preliminary comparison to the observations shows that the predicted redshift distortion parameter is in good agreement with the recent determination of Blomqvist et al., but the density bias factor is lower than observed. We make all our results publicly available in the form of tables of the non-linear power spectrum that is directly obtained from all our simulations, and parameters of our fitting formula.

Small-scale structure and the Lyman-α forest baryon acoustic oscillation feature

“…The simulations by Arinyo-i-Prats et al (2015) 9 find bF = −0.201 and βF = 1.205 (z = 3.0), and bF = −0.125 and βF = 1.364 (z = 2.5, interpolated). Numerical values are not reported for bF Γ, but by applying the integral form to the observed flux probability density functions (Kim et al 2007 , Table A3), we find bF Γ = 0.156 (z = 3.0) and 0.122 (z = 2.5).…”

Baryon acoustic oscillations from the complete SDSS-III Lyα-quasar cross-correlation function at z = 2.4

“…It can be chosen to be of one of the two forms given by Equation 21 of (McDonald 2003) or as presented in Arinyo-i-Prats et al (2015). Our standard fit uses the former.…”

Lyman- α constraints on ultralight scalar dark matter: Implications for the early and late universe

“…There have been several studies in the past (e.g. [18,27,28]), that have shown that the Lyman-α forest is really measuring the amplitude of the linear matter power spectrum, the slope of the power spectrum, and possibly the effective running, all evaluated at a pivot scale of around 1-10 Mpc/h. Thus σ 8 and n eff used are good tracers of what is actually measured.…”