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Register a new userConstraints on neutrino masses from Lyman-alpha forest power spectrum with BOSS and XQ-100
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We present constraints on masses of active and sterile neutrinos. We use the one-dimensional Ly$alpha$-forest power spectrum from the Baryon Oscillation Spectroscopic Survey (BOSS) of the Sloan Digital Sky Survey (SDSS-III) and from the VLT/XSHOOTER legacy survey (XQ-100). In this paper, we present our own measurement of the power spectrum with the publicly released XQ-100 quasar spectra. Fitting Ly$alpha$ data alone leads to cosmological parameters in excellent agreement with the values derived independently from Planck 2015 Cosmic Microwave Background (CMB) data. Combining BOSS and XQ-100 Ly$alpha$ power spectra, we constrain the sum of neutrino masses to $sum m_ u < 0.8$ eV (95% C.L). With the addition of CMB data, this bound is tightened to $sum m_ u < 0.14$ eV (95% C.L.). With their sensitivity to small scales, Ly$alpha$ data are ideal to constrain $Lambda$WDM models. Using XQ-100 alone, we issue lower bounds on pure dark matter particles: $m_X gtrsim 2.08 : rm{keV}$ (95% C.L.) for early decoupled thermal relics, and $m_s gtrsim 10.2 : rm{keV}$ (95% C.L.) for non-resonantly produced right-handed neutrinos. Combining the 1D Ly$alpha$ forest power spectrum measured by BOSS and XQ-100, we improve the two bounds to $m_X gtrsim 4.17 : rm{keV}$ and $m_s gtrsim 25.0 : rm{keV}$ (95% C.L.). The $3~sigma$ bound shows a more significant improvement, increasing from $m_X gtrsim 2.74 : rm{keV}$ for BOSS alone to $m_X gtrsim 3.10 : rm{keV}$ for the combined BOSS+XQ-100 data set. Finally, we include in our analysis the first two redshift bins ($z=4.2$ and $z=4.6$) of the power spectrum measured with the high-resolution HIRES/MIKE spectrographs. The addition of HIRES/MIKE power spectrum allows us to further improve the two limits to $m_X gtrsim 4.65 : rm{keV}$ and $m_s gtrsim 28.8 : rm{keV}$ (95% C.L.).
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We present the Lyman-$alpha$ flux power spectrum measurements of the XQ-100 sample of quasar spectra obtained in the context of the European Southern Observatory Large Programme Quasars and their absorption lines: a legacy survey of the high redshift universe with VLT/XSHOOTER. Using $100$ quasar spectra with medium resolution and signal-to-noise ratio we measure the power spectrum over a range of redshifts $z = 3 - 4.2$ and over a range of scales $k = 0.003 - 0.06,mathrm{s,km^{-1}}$. The results agree well with the measurements of the one-dimensional power spectrum found in the literature. The data analysis used in this paper is based on the Fourier transform and has been tested on synthetic data. Systematic and statistical uncertainties of our measurements are estimated, with a total error (statistical and systematic) comparable to the one of the BOSS data in the overlapping range of scales, and smaller by more than $50%$ for higher redshift bins ($z>3.6$) and small scales ($k > 0.01,mathrm{s,km^{-1}}$). The XQ-100 data set has the unique feature of having signal-to-noise ratios and resolution intermediate between the two data sets that are typically used to perform cosmological studies, i.e. BOSS and high-resolution spectra (e.g. UVES/VLT or HIRES). More importantly, the measured flux power spectra span the high redshift regime which is usually more constraining for structure formation models.
We present constraints on neutrino masses, the primordial fluctuation spectrum from inflation, and other parameters of the $Lambda$CDM model, using the one-dimensional Ly$alpha$-forest power spectrum measured by Palanque-Delabrouille et al. (2013) from SDSS-III/BOSS, complemented by Planck 2015 cosmic microwave background (CMB) data and other cosmological probes. This paper improves on the previous analysis by Palanque-Delabrouille et al. (2015) by using a more powerful set of calibrating hydrodynamical simulations that reduces uncertainties associated with resolution and box size, by adopting a more flexible set of nuisance parameters for describing the evolution of the intergalactic medium, by including additional freedom to account for systematic uncertainties, and by using Planck 2015 constraints in place of Planck 2013. Fitting Ly$alpha$ data alone leads to cosmological parameters in excellent agreement with the values derived independently from CMB data, except for a weak tension on the scalar index $n_s$. Combining BOSS Ly$alpha$ with Planck CMB constrains the sum of neutrino masses to $sum m_ u < 0.12$ eV (95% C.L.) including all identified systematic uncertainties, tighter than our previous limit (0.15 eV) and more robust. Adding Ly$alpha$ data to CMB data reduces the uncertainties on the optical depth to reionization $tau$, through the correlation of $tau$ with $sigma_8$. Similarly, correlations between cosmological parameters help in constraining the tensor-to-scalar ratio of primordial fluctuations $r$. The tension on $n_s$ can be accommodated by allowing for a running ${mathrm d}n_s/{mathrm d}ln k$. Allowing running as a free parameter in the fits does not change the limit on $sum m_ u$. We discuss possible interpretations of these results in the context of slow-roll inflation.
The Lyman-alpha forest is the large-scale structure probe for which we appear to have modeling control to the highest wavenumbers, which makes it of great interest for constraining the warmness/fuzziness of the dark matter and the timing of reionization processes. However, the standard statistic, the Lyman-alpha forest power spectrum, is unable to strongly constrain the IGM temperature-density relation, and this inability further limits how well other high wavenumber-sensitive parameters can be constrained. With the aim of breaking these degeneracies, we measure the power spectrum of the Lyman-beta forest and its cross correlation with the coeveal Lyman-alpha forest using the one hundred spectra of z=3.5-4.5 quasars in the VLT/X-Shooter XQ-100 Legacy Survey, motivated by the Lyman-beta transitions smaller absorption cross section that makes it sensitive to somewhat higher densities relative to the Lyman-alpha transition. Our inferences from this measurement for the IGM temperature-density relation appear to latch consistently onto the recent tight lower-redshift Lyman-alpha forest constraints of arXiv:2009.00016v1 [astro-ph.CO]. The z=3.4-4.7 trends we find using the Lyman-alpha--Lyman-beta cross correlation show a flattening of the slope of the temperature-density relation with decreasing redshift. This is the trend anticipated from ongoing HeII reionization and there being sufficient time to reach the asymptotic temperature-density slope after hydrogen reionization completes. Furthermore, our measurements provide a consistency check on IGM models that explain the Lyman-alpha forest, with the cross correlation being immune to systematics that are uncorrelated between the two forests, such as metal line contamination.
We measure the 1D Ly$,alpha$ power spectrum poned from Keck Observatory Database of Ionized Absorption toward Quasars (KODIAQ), The Spectral Quasar Absorption Database (SQUAD) and XQ-100 quasars using the optimal quadratic estimator. We combine KODIAQ and SQUAD at the spectrum level, but perform a separate XQ-100 estimation to control its large resolution corrections in check. Our final analysis measures poned at scales $k<0.1,$s$,$km$^{-1}$ between redshifts $z=$ 2.0 -- 4.6 using 538 quasars. This sample provides the largest number of high-resolution, high-S/N observations; and combined with the power of optimal estimator it provides exceptional precision at small scales. These small-scale modes ($kgtrsim 0.02,$s$,$km$^{-1}$), unavailable in Sloan Digital Sky Survey (SDSS) and Dark Energy Spectroscopic Instrument (DESI) analyses, are sensitive to the thermal state and reionization history of the intergalactic medium, as well as the nature of dark matter. As an example, a simple Fisher forecast analysis estimates that our results can improve small-scale cut off sensitivity by more than a factor of 2.
We have developed two independent methods to measure the one-dimensional power spectrum of the transmitted flux in the Lyman-$alpha$ forest. The first method is based on a Fourier transform, and the second on a maximum likelihood estimator. The two methods are independent and have different systematic uncertainties. The determination of the noise level in the data spectra was subject to a novel treatment, because of its significant impact on the derived power spectrum. We applied the two methods to 13,821 quasar spectra from SDSS-III/BOSS DR9 selected from a larger sample of over 60,000 spectra on the basis of their high quality, large signal-to-noise ratio, and good spectral resolution. The power spectra measured using either approach are in good agreement over all twelve redshift bins from $<z> = 2.2$ to $<z> = 4.4$, and scales from 0.001 $rm(km/s)^{-1}$ to $0.02 rm(km/s)^{-1}$. We determine the methodological and instrumental systematic uncertainties of our measurements. We provide a preliminary cosmological interpretation of our measurements using available hydrodynamical simulations. The improvement in precision over previously published results from SDSS is a factor 2--3 for constraints on relevant cosmological parameters. For a $Lambda$CDM model and using a constraint on $H_0$ that encompasses measurements based on the local distance ladder and on CMB anisotropies, we infer $sigma_8 =0.83pm0.03$ and $n_s= 0.97pm0.02$ based on ion{H}{i} absorption in the range $2.1<z<3.7$.
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