The 3D Lyman- α forest power spectrum from eBOSS DR16

Journal Article · 31 August 2024 · Monthly Notices of the Royal Astronomical Society

DOI: https://doi.org/10.1093/mnras/stae2035 · OSTI ID:2439785

de Belsunce, Roger ; Philcox, Oliver H. E. ; Iršič, Vid; McDonald, Patrick; Guy, Julien; Palanque-Delabrouille, Nathalie

ABSTRACT We measure the three-dimensional power spectrum (P3D) of the transmitted flux in the Lyman-$$\alpha$$ (Ly $$\alpha$$) forest using the complete extended Baryon Oscillation Spectroscopic Survey data release 16 (eBOSS DR16). This sample consists of $$\sim$$205 000 quasar spectra in the redshift range $$2\le z \le 4$$ at an effective redshift $z=2.334$. We propose a pair-count spectral estimator in configuration space, weighting each pair by $$\exp (i\mathbf {k}\cdot \mathbf {r})$$, for wave vector $$\mathbf {k}$$ and pixel pair separation $$\mathbf {r}$$, effectively measuring the anisotropic power spectrum without the need for fast Fourier transforms. This accounts for the window matrix in a tractable way, avoiding artefacts found in Fourier-transform based power spectrum estimators due to the sparse sampling transverse to the line of sight of Ly $$\alpha$$ skewers. We extensively test our pipeline on two sets of mocks: (i) idealized Gaussian random fields with a sparse sampling of Ly $$\alpha$$ skewers, and (ii) log-normal LyaCoLoRe mocks including realistic noise levels, the eBOSS survey geometry and contaminants. On eBOSS DR16 data, the Kaiser formula with a non-linear correction term obtained from hydrodynamic simulations yields a good fit to the power spectrum data in the range $$(0.02 \le k \le 0.35)\, h\, {\rm Mpc}^{-1}\,$$ at the 1–2σ level with a covariance matrix derived from LyaCoLoRe mocks. We demonstrate a promising new approach for full-shape cosmological analyses of Ly $$\alpha$$ forest data from cosmological surveys such as eBOSS, the currently observing Dark Energy Spectroscopic Instrument and future surveys such as the Prime Focus Spectrograph, WEAVE-QSO, and 4MOST.

• Sponsoring Organization: USDOE
• Grant/Contract Number: AC02-05CH11231
• OSTI ID: 2439785
• Journal Information: Monthly Notices of the Royal Astronomical Society, Journal Name: Monthly Notices of the Royal Astronomical Society Journal Issue: 3 Vol. 533; ISSN 0035-8711
• Publisher: Oxford University PressCopyright Statement
• Country of Publication: United Kingdom
• Language: English