Cosmology beyond BAO from the 3D distribution of the Lyman-α forest. Issue 4 (20th July 2021)

• Record Type: Journal Article
• Authors: Cuceu, Andrei; Font-Ribera, Andreu; Joachimi, Benjamin; Nadathur, Seshadri
• Is Part Of: Monthly notices of the Royal Astronomical Society. Volume 506:Issue 4(2021)
• Page Start: 5439
• Page End: 5450
• Publication Date: 2021-07-20
• Subjects: methods: data analysis -- cosmological parameters -- large-scale structure of Universe; Astronomy -- Periodicals; Periodicals; 520.5
• DOI: 10.1093/mnras/stab1999
• Languages: English
• ISSNs: 0035-8711

Abstract

ABSTRACT: We propose a new method for fitting the full-shape of the Lyman-α (Ly α) forest 3D correlation function in order to measure the Alcock-Paczynski (AP) effect. Our method preserves the robustness of baryon acoustic oscillations (BAO) analyses, while also providing extra cosmological information from a broader range of scales. We compute idealized forecasts for the Dark Energy Spectroscopic Instrument (DESI) using the Ly α autocorrelation and its cross-correlation with quasars, and show how this type of analysis improves cosmological constraints. The DESI Ly α BAO analysis is expected to measure H ( z eff ) r d and D M ( z eff )/ r d with a precision of $\sim 0.9{{\ \rm per\ cent}}$, where H is the Hubble parameter, r d is the comoving BAO scale, D M is the comoving angular diameter distance, and the effective redshift of the measurement is z eff ≃ 2.3. By fitting the AP parameter from the full shape of the two correlations, we show that we can obtain a precision of $\sim 0.5-0.6{{\ \rm per\ cent}}$ on each of H ( z eff ) r d and D M ( z eff )/ r d . Furthermore, we show that a joint full-shape analysis of the Ly α auto and cross-correlation with quasars can measure the linear growth rate times the amplitude of matter fluctuations in spheres of 8 h −1 Mpc, f σ8 ( z eff ). Such an analysis could provide the first ever measurement of f σ8 ( z eff ) at redshift z eff > 2. By combining this with the quasar autocorrelation in a joint analysis of the three high-redshift two-point correlation functions, we show that DESI could be able to measure f σ8 ( z eff ≃ 2.3) with a precision of $5-12{{\ \rm per\ cent}}$, depending on the smallest scale fitted.