TY - JOUR
T1 - Broadband distortion modeling in Lyman-α forest BAO fitting
AU - Blomqvist, Michael
AU - Kirkby, David
AU - Bautista, Julian E.
AU - Arinyo-I-Prats, Andreu
AU - Busca, Nicolás G.
AU - Miralda-Escudé, Jordi
AU - Slosar, Anže
AU - Font-Ribera, Andreu
AU - Margala, Daniel
AU - Schneider, Donald P.
AU - Vazquez, Jose A.
PY - 2015/11/23
Y1 - 2015/11/23
N2 - In recent years, the Lyman-α absorption observed in the spectra of high-redshift quasars has been used as a tracer of large-scale structure by means of the three-dimensional Lyman-α forest auto-correlation function at redshift z 2.3, but the need to fit the quasar continuum in every absorption spectrum introduces a broadband distortion that is difficult to correct and causes a systematic error for measuring any broadband properties. We describe a k-space model for this broadband distortion based on a multiplicative correction to the power spectrum of the transmitted flux fraction that suppresses power on scales corresponding to the typical length of a Lyman-α forest spectrum. Implementing the distortion model in fits for the baryon acoustic oscillation (BAO) peak position in the Lyman-α forest auto-correlation, we find that the fitting method recovers the input values of the linear bias parameter bF and the redshift-space distortion parameter βF for mock data sets with a systematic error of less than 0.5%. Applied to the auto-correlation measured for BOSS Data Release 11, our method improves on the previous treatment of broadband distortions in BAO fitting by providing a better fit to the data using fewer parameters and reducing the statistical errors on βF and the combination bF(1+βF) by more than a factor of seven. The measured values at redshift z=2.3 are βF=1.39+0.11 +0.24 +0.38 -0.10 -0.19 -0.28 and bF(1+βF)=-0.374+0.007 +0.013 +0.020 -0.007 -0.014 -0.022 (1σ, 2σ and 3σ statistical errors). Our fitting software and the input files needed to reproduce our main results are publicly available.
AB - In recent years, the Lyman-α absorption observed in the spectra of high-redshift quasars has been used as a tracer of large-scale structure by means of the three-dimensional Lyman-α forest auto-correlation function at redshift z 2.3, but the need to fit the quasar continuum in every absorption spectrum introduces a broadband distortion that is difficult to correct and causes a systematic error for measuring any broadband properties. We describe a k-space model for this broadband distortion based on a multiplicative correction to the power spectrum of the transmitted flux fraction that suppresses power on scales corresponding to the typical length of a Lyman-α forest spectrum. Implementing the distortion model in fits for the baryon acoustic oscillation (BAO) peak position in the Lyman-α forest auto-correlation, we find that the fitting method recovers the input values of the linear bias parameter bF and the redshift-space distortion parameter βF for mock data sets with a systematic error of less than 0.5%. Applied to the auto-correlation measured for BOSS Data Release 11, our method improves on the previous treatment of broadband distortions in BAO fitting by providing a better fit to the data using fewer parameters and reducing the statistical errors on βF and the combination bF(1+βF) by more than a factor of seven. The measured values at redshift z=2.3 are βF=1.39+0.11 +0.24 +0.38 -0.10 -0.19 -0.28 and bF(1+βF)=-0.374+0.007 +0.013 +0.020 -0.007 -0.014 -0.022 (1σ, 2σ and 3σ statistical errors). Our fitting software and the input files needed to reproduce our main results are publicly available.
KW - baryon acoustic oscillations
KW - cosmological parameters from LSS
KW - dark energy experiments
KW - Lyman alpha forest
UR - http://www.scopus.com/inward/record.url?scp=84948757054&partnerID=8YFLogxK
U2 - 10.1088/1475-7516/2015/11/034
DO - 10.1088/1475-7516/2015/11/034
M3 - Article
AN - SCOPUS:84948757054
SN - 1475-7516
VL - 2015
JO - Journal of Cosmology and Astroparticle Physics
JF - Journal of Cosmology and Astroparticle Physics
IS - 11
M1 - 034
ER -