The Linear Theory Power Spectrum from the Lyα Forest in the Sloan Digital Sky Survey

Abstract

We analyze the SDSS Lyα forest P F (k, z) measurement to determine the linear theory power spectrum. Our analysis is based on fully hydrodynamic simulations, extended using hydro-PM simulations. We account for the effect of absorbers with damping wings, which leads to an increase in the slope of the linear power spectrum. We break the degeneracy between the mean level of absorption and the linear power spectrum without significant use of external constraints. We infer linear theory power spectrum amplitude ∆ 2 L (k p = 0.009 s/km, z p = 3.0) = 0.452 +0.069 +0.141 −0.057 −0.116 and slope n eff (k p , z p ) = −2.321 +0.055 +0.131 −0.047 −0.102 (possible systematic errors are included through nuisance parameters in the fit -a factor 5 smaller errors would be obtained on both parameters if we ignored modeling uncertainties). The errors are correlated and not perfectly Gaussian, so we provide a χ 2 table to accurately describe the results. The result corresponds to σ 8 = 0.85, n = 0.94, for a ΛCDM model with Ω m = 0.3, Ω b = 0.04, and h = 0.7, but is most useful in a combined fit with the CMB. The inferred curvature of the linear power spectrum and the evolution of its amplitude and slope with -2redshift are consistent with expectations for ΛCDM models, with the evolution of the slope, in particular, being tightly constrained. We use this information to constrain systematic contamination, e.g., fluctuations in the UV background. This paper should serve as a starting point for more work to refine the analysis, including technical improvements such as increasing the size and number of the hydrodynamic simulations, and improvements in the treatment of the various forms of feedback from galaxies and quasars.Subject headings: cosmology: theory-intergalactic medium-large-scale structure of universe-quasars: absorption lines

A principal component analysis of quasar UV spectra atz ~ 3

“…To our knowledge, one attempt has also been made to derive a similar decomposition at high redshift using SDSS spectra by McDonald et al (2005). These authors comment that this continuum determination is robust enough to infer the mean flux evolution, but unstable as far as the Lyman-α power spectrum is concerned.…”

“…Petitjean et al 1998;Croft et al 1998;McDonald et al 2005;Theuns & Srianand 2006). The next generation of quasar surveys from BOSS (SDSS-III, Schlegel et al 2007;Eisenstein et al 2011) to Big-BOSS (Schlegel et al 2009) should provide the first detection of baryonic acoustic oscillations in the IGM at z ∼ 2−3 (Slosar et al 2009;White et al 2010).…”

“…Intermediate resolution data have been used as well (McDonald et al 2005;Dall'Aglio et al 2009) but the feature was not detected. However, the methods used may not be entirely appropriate and we come back to this point in the present A&A 530, A50 (2011) paper.…”

On the intergalactic temperature–density relation

“…This relation is established ∆z ∼ 1 − 2 after the end of cosmological reionization processes (Hui & Gnedin 1997;Trac et al 2008;Furlanetto & Oh 2009;McQuinn et al 2009). Motivated by this limiting behavior, a power-law parameterization for the thermal state is adopted in almost all analyses of the Lyα forest (e.g., McDonald et al 2005;Viel et al 2006;Lidz et al 2010). 1 Here we provide a simple explanation for the physics that sets the asymptotic relation as well as an understanding for how quickly this asymptote is reached.…”

SUSY SU(5)×S 4 GUT flavor model for fermion masses and mixings with adjoint, large θ 13 PMNS

“…The plot of the ratio |m 3 /m 2 | and sum of light neutrino mass k m k as function of the lightest neutrino mass m lightest , which is m 1 (m 3 ) for NH (IH) mass spectrum, are shown in figure 3(a) and figure 3(b), respectively. Note that the horizontal lines in figure 3(b) represents the cosmological bound at 0.19 eV (black), corresponding to the combined observational data from [113][114][115][116][117][118][119][120][121][122], and the upper bounds 0.23 eV from Planck [123]. The ratio tends to a degenerate mass spectrum in both cases as the value of m lightest → 0.1eV which is disfavoured in the model.…”