Detection of Lyβauto-correlations and Lyα-Lyβcross-correlations in BOSS Data Release 9

Abstract

The Lyman-$\beta$ forest refers to a region in the spectra of distant quasars that lies between the rest-frame Lyman-$\beta$ and Lyman-$\gamma$ emissions. The forest in this region is dominated by a combination of absorption due to resonant Ly$\alpha$ and Ly$\beta$ scattering. When considering the 1D Ly$\beta$ forest in addition to the 1D Ly$\alpha$ forest, the full statistical description of the data requires four 1D power spectra: Ly$\alpha$ and Ly$\beta$ auto-power spectra and the Ly$\alpha$-Ly$\beta$ real and imaginary cross-power spectra. We describe how these can be measured using an optimal quadratic estimator that naturally disentangles Ly$\alpha$ and Ly$\beta$ contributions. Using a sample of approximately 60,000 quasar sight-lines from the BOSS Data Release 9, we make the measurement of the one-dimensional power spectrum of fluctuations due to the Ly$\beta$ resonant scattering. While we have not corrected our measurements for resolution damping of the power and other systematic effects carefully enough to use them for cosmological constraints, we can robustly conclude the following: i) Ly$\beta$ power spectrum and Ly$\alpha$-Ly$\beta$ cross spectra are detected with high statistical significance; ii) the cross-correlation coefficient is $\approx 1$ on large scales; iii) the Ly$\beta$ measurements are contaminated by the associated OVI absorption, which is analogous to the SiIII contamination of the Ly$\alpha$ forest. Measurements of the Ly$\beta$ forest will allow extension of the usable path-length for the Ly$\alpha$ measurements while allowing a better understanding of the physics of intergalactic medium and thus more robust cosmological constraints.

26 pages, 10 figures; matches version accepted by JCAP

References in corpus (4)

• The 2.5 m Telescope of the Sloan Digital Sky Survey
• Baryon Acoustic Oscillations in the Ly-α forest of BOSS quasars
• The one-dimensional Ly-alpha forest power spectrum from BOSS
• Think Outside the Color Box: Probabilistic Target Selection and the SDSS-XDQSO Quasar Targeting Catalog

Cited by in corpus (14)

• The Completed SDSS-IV extended Baryon Oscillation Spectroscopic Survey: Baryon acoustic oscillations with Lyman-$\alpha$ forests
• DESI and other dark energy experiments in the era of neutrino mass measurements
• Baryon acoustic oscillations at z = 2.34 from the correlations of Ly$\alpha$ absorption in eBOSS DR14
• Revealing reionization with the thermal history of the intergalactic medium: new constraints from the Lyman-$\alpha$ flux power spectrum
• The Lyman-alpha forest power spectrum from the XQ-100 Legacy Survey
• Large-scale 3D mapping of the intergalactic medium using the Lyman Alpha Forest
• The Alcock-Paczyński effect from Lyman-$\alpha$ forest correlations: Analysis validation with synthetic data
• Measurements of effective optical depth in the Ly$\alpha$ forest from the BOSS DR12 Quasar sample
• A measurement of the Lyman-beta forest power spectrum and its cross with the Lyman-alpha forest in X-Shooter XQ-100
• The C IV forest as a probe of baryon acoustic oscillations
• Metal Lines Associated with the Lyman-alpha Forest from eBOSS Data
• The Lyman-beta forest as a cosmic thermometer
• Background power subtraction in Lyman-alpha forest
• Weighing Cosmic Structures with Clusters of Galaxies and the Intergalactic Medium