Optimal 1D Ly$\alpha$ Forest Power Spectrum Estimation -- II. KODIAQ, SQUAD & XQ-100

TL;DR

This paper presents precise measurements of the 1D Lyα forest power spectrum from high-resolution quasar spectra, enhancing understanding of the intergalactic medium and dark matter by analyzing small-scale modes with an optimal quadratic estimator.

Contribution

It introduces an improved measurement of the Lyα power spectrum at small scales using an optimal quadratic estimator on a large high-resolution quasar sample, surpassing previous surveys in precision.

Findings

Measured power spectrum at scales k<0.1 s/km and redshifts 2.0-4.6.

Achieved exceptional small-scale measurement precision.

Forecast indicates potential to double sensitivity to the small-scale cutoff.

Abstract

We measure the 1D Ly$\,\alpha$ power spectrum $P_\mathrm{1D}$ from Keck Observatory Database of Ionized Absorption toward Quasars (KODIAQ), The Spectral Quasar Absorption Database (SQUAD) and XQ-100 quasars using the optimal quadratic estimator. We combine KODIAQ and SQUAD at the spectrum level, but perform a separate XQ-100 estimation to control its large resolution corrections in check. Our final analysis measures $P_\mathrm{1D}$ at scales $k<0.1\,$s$\,$km$^{-1}$ between redshifts $z=$ 2.0 -- 4.6 using 538 quasars. This sample provides the largest number of high-resolution, high-S/N observations; and combined with the power of optimal estimator it provides exceptional precision at small scales. These small-scale modes ($k\gtrsim 0.02\,$s$\,$km$^{-1}$), unavailable in Sloan Digital Sky Survey (SDSS) and Dark Energy Spectroscopic Instrument (DESI) analyses, are sensitive to the thermal state and reionization history of the intergalactic medium, as well as the nature of dark matter. As an example, a simple Fisher forecast analysis estimates that our results can improve small-scale cut off sensitivity by more than a factor of 2.