44 research outputs found
Novel constraints on noncold, nonthermal dark matter from Lyman-alpha forest data
In this paper, we present an efficient method for constraining both thermal and nonthermal dark matter (DM) scenarios with the Lyman-\u3b1 forest based on a simple and flexible parametrization capable of reproducing the small-scale clustering signal of a large set of noncold DM (NCDM) models. We extract new limits on the fundamental DM properties through an extensive analysis of the high resolution, high redshift data obtained by the MIKE/HIRES spectrographs. By using a large suite of hydrodynamical simulations, we determine constraints on both astrophysical, cosmological, and NCDM parameters by performing a full Monte Carlo Markov chain analysis. We obtain a marginalized upper limit on the largest possible scale at which a power suppression induced by nearly any NCDM scenario can occur, i.e., \u3b1<0.03 Mpc/h (2\u3c3 C.L.). We explicitly describe how to test several of the most viable NCDM scenarios without the need to run any specific numerical simulations due to the novel parametrization proposed and due to a new scheme that interpolates between the cosmological models explored. The shape of the linear matter power spectrum for standard thermal warm DM models appears to be in mild tension ( 3c2\u3c3 C.L.) with the data compared to nonthermal scenarios. We show that a DM fluid composed by both a warm (thermal) and a cold component is also in tension with the Lyman-\u3b1 forest, at least for large \u3b1 values. This is the first study that allows us to probe the linear small-scale shape of the DM power spectrum for a large set of NCDM models
Canonical Hubble-Tension-Resolving Early Dark Energy Cosmologies are Inconsistent with the Lyman- Forest
Current cosmological data exhibit discordance between indirect and some
direct inferences of the present-day expansion rate, . Early dark energy
(EDE), which briefly increases the cosmic expansion rate prior to
recombination, is a leading scenario for resolving this "Hubble tension" while
preserving a good fit to cosmic microwave background (CMB) data. However, this
comes at the cost of changes in parameters that affect structure formation in
the late-time universe, including the spectral index of scalar perturbations,
. Here, we present the first constraints on axion-like EDE using data from
the Lyman- forest, i.e., absorption lines imprinted in background
quasar spectra by neutral hydrogen gas along the line of sight. We consider two
independent measurements of the one-dimensional Ly forest flux power
spectrum, from the Sloan Digital Sky Survey (SDSS eBOSS) and from the
MIKE/HIRES and X-Shooter spectrographs. We combine these with a baseline
dataset comprised of Planck CMB data and baryon acoustic oscillation (BAO)
measurements. Combining the eBOSS Ly data with the CMB and BAO dataset
reduces the 95% confidence level (CL) upper bound on the maximum fractional
contribution of EDE to the cosmic energy budget, , from 0.07 to
0.03 and constrains km/s/Mpc (68% CL), with maximum a
posteriori value km/s/Mpc. Similar results are obtained for the
MIKE/HIRES and X-Shooter Ly data. Our Ly-based EDE constraints
yield values that are in tension with the SH0ES
distance-ladder measurement and are driven by the preference of the Ly
forest data for values lower than those required by EDE cosmologies that
fit Planck CMB data. Taken at face value, the Ly forest severely
constrains canonical EDE models that could resolve the Hubble tension.Comment: 7+9 pages, 2+9 figures, accepted by Phys. Rev. Let
First Constraints on Fuzzy Dark Matter from Lyman-α Forest Data and Hydrodynamical Simulations.
We present constraints on the masses of extremely light bosons dubbed fuzzy dark matter (FDM) from Lyman-α forest data. Extremely light bosons with a de Broglie wavelength of ∼1 kpc have been suggested as dark matter candidates that may resolve some of the current small scale problems of the cold dark matter model. For the first time, we use hydrodynamical simulations to model the Lyman-α flux power spectrum in these models and compare it to the observed flux power spectrum from two different data sets: the XQ-100 and HIRES/MIKE quasar spectra samples. After marginalization over nuisance and physical parameters and with conservative assumptions for the thermal history of the intergalactic medium (IGM) that allow for jumps in the temperature of up to 5000 K, XQ-100 provides a lower limit of 7.1×10^{-22} eV, HIRES/MIKE returns a stronger limit of 14.3×10^{-22} eV, while the combination of both data sets results in a limit of 20×10^{-22} eV (2σ C.L.). The limits for the analysis of the combined data sets increases to 37.5×10^{-22} eV (2σ C.L.) when a smoother thermal history is assumed where the temperature of the IGM evolves as a power law in redshift. Light boson masses in the range 1-10×10^{-22} eV are ruled out at high significance by our analysis, casting strong doubts that FDM helps solve the "small scale crisis" of the cold dark matter models
Data compression of measurements of peculiar velocities of Supernovae Ia
We study the compression of information present in the correlated
perturbations to the luminosity distance in the low-redshift ()
supernovae Ia due to peculiar velocities of these supernovae. We demonstrate
that the na\"{i}ve compression into angular velocity power spectrum does not
work efficiently, due to thickness of the spherical shell over which the
supernovae are measured. Instead, we show that measurements can be compressed
into measurements of , where is the logarithmic rate of growth of
linear perturbations and is their power spectrum. We develop an optimal
quadratic estimator and show that it recovers all information for
models for surveys of or more supernovae. We explicitly
demonstrate robustness with respect to the assumed fiducial model and the
number of power spectrum bins. Using mock catalogues of SNe Ia we estimate that
future low redshift surveys will be able to probe to 6% accuracy
with SNe Ia.Comment: Accepted to PRD; Added referenc
Possible evidence for a large-scale enhancement in the Lyman- forest power spectrum at redshift
Inhomogeneous reionization enhances the 1D Lyman- forest power
spectrum on large scales at redshifts . This is due to coherent
fluctuations in the ionized hydrogen fraction that arise from large-scale
variations in the post-reionization gas temperature, which fade as the gas
cools. It is therefore possible to use these relic fluctuations to constrain
inhomogeneous reionization with the power spectrum at wavenumbers
. We use the Sherwood-Relics suite
of hybrid radiation hydrodynamical simulations to perform a first analysis of
new Lyman- forest power spectrum measurements at .
These data extend to wavenumbers , with
a relative uncertainty of -- per cent in each wavenumber bin. Our
analysis returns a preference for an enhancement in the
Lyman- forest power spectrum at large scales, in excess of that
expected for a spatially uniform ultraviolet background. This large-scale
enhancement could be a signature of inhomogeneous reionization, although the
statistical precision of these data is not yet sufficient for obtaining a
robust detection of the relic post-reionization fluctuations. We show that
future power spectrum measurements with relative uncertainties of per cent should provide unambiguous evidence for an enhancement in the
power spectrum on large scales.Comment: Accepted by MNRAS, 13 pages, 8 figure
Detection of Ly\beta auto-correlations and Ly\alpha-Ly\beta cross-correlations in BOSS Data Release 9
The Lyman- forest refers to a region in the spectra of distant quasars
that lies between the rest-frame Lyman- and Lyman- emissions.
The forest in this region is dominated by a combination of absorption due to
resonant Ly and Ly scattering. When considering the 1D Ly
forest in addition to the 1D Ly forest, the full statistical
description of the data requires four 1D power spectra: Ly and
Ly auto-power spectra and the Ly-Ly real and imaginary
cross-power spectra. We describe how these can be measured using an optimal
quadratic estimator that naturally disentangles Ly and Ly
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 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 power
spectrum and Ly-Ly cross spectra are detected with high
statistical significance; ii) the cross-correlation coefficient is
on large scales; iii) the Ly measurements are contaminated by the
associated OVI absorption, which is analogous to the SiIII contamination of the
Ly forest. Measurements of the Ly forest will allow extension of
the usable path-length for the Ly measurements while allowing a better
understanding of the physics of intergalactic medium and thus more robust
cosmological constraints.Comment: 26 pages, 10 figures; matches version accepted by JCA
Particle initialization effects on Lyman-α forest statistics in cosmological SPH simulations
Confronting measurements of the Lyman-α forest with cosmological hydrodynamical simulations has produced stringent constraints on models of particle dark matter and the thermal and ionization state of the intergalactic medium. We investigate the robustness of such models of the Lyman-α forest, focussing on the effect of particle initial conditions on the Lyman-α forest statistics in cosmological SPH simulations. We study multiple particle initialization algorithms in simulations that are designed to be identical in other respects. In agreement with the literature, we find that the correct linear theory evolution is obtained when a glass-like configuration is used for initial unperturbed gas particle positions alongside a regular grid configuration for dark matter particles and the use of non-identical initial density perturbations for gas and dark matter. However, we report that this introduces a large scale-dependent distortion in the one-dimensional Lyman-α transmission power spectrum at small scales (k > 0.05 s/km). The effect is close to 50 % at k ∼ 0.1 s/km, and persists at higher resolution. This can severely bias inferences in parameters such as the dark matter particle mass. By considering multiple initial conditions codes and their variations, we also study the impact of a variety of other assumptions and algorithmic choices, such as adaptive softening, background radiation density, particle staggering, and perturbation theory accuracy, on the matter power spectrum, the Lyman-α flux power spectrum, and the Lyman-α flux PDF. This work reveals possible pathways towards more accurate theoretical models of the Lyman-α forest to match the quality of upcoming measurements
Unveiling Dark Matter free-streaming at the smallest scales with high redshift Lyman-alpha forest
This study introduces novel constraints on the free-streaming of thermal
relic warm dark matter (WDM) from Lyman- forest flux power spectra. Our
analysis utilises a high-resolution, high-redshift sample of quasar spectra
observed using the HIRES and UVES spectrographs (). We employ a
Bayesian inference framework and a simulation-based likelihood that encompasses
various parameters including the free-streaming of dark matter, cosmological
parameters, the thermal history of the intergalactic medium, and inhomogeneous
reionization, to establish lower limits on the mass of a thermal relic WDM
particle of (at 95\% C.L.). This result surpasses previous
limits from the Lyman- forest through reduction of the measured
uncertainties due to a larger statistical sample and by measuring clustering to
smaller scales (). The approximately
two-fold improvement due to the expanded statistical sample suggests that the
effectiveness of Lyman- forest constraints on WDM models at high
redshifts are limited by the availability of high-quality quasar spectra.
Restricting the analysis to comparable scales and thermal history priors as in
prior studies () lowers the bound on the
WDM mass to . As the precision of the measurements
increases, it becomes crucial to examine the instrumental and modelling
systematics. On the modelling front, we argue that the impact of the thermal
history uncertainty on the WDM particle mass constraint has diminished due to
improved independent observations. At the smallest scales, the primary source
of modeling systematic arises from the structure in the peculiar velocity of
the intergalactic medium and inhomogeneous reionization.Comment: 22 pages, 14 figures, 2 tables; submitte
Possible evidence for a large-scale enhancement in the Lyman-α forest power spectrum at redshift z ≥ 4
Inhomogeneous reionization enhances the 1D Lyα forest power spectrum on large scales at redshifts z ≥ 4. This is due to coherent fluctuations in the ionized hydrogen fraction that arise from large-scale variations in the post-reionization gas temperature, which fade as the gas cools. It is therefore possible to use these relic fluctuations to constrain inhomogeneous reionization with the power spectrum at wavenumbers log10(k/km−1 s) ≲ −1.5. We use the Sherwood-Relics suite of hybrid radiation hydrodynamical simulations to perform a first analysis of new Lyα forest power spectrum measurements at 4.0 ≤ z ≤ 4.6. These data extend to wavenumbers log10(k/km−1 s) ≃ −3, with a relative uncertainty of 10–20 per cent in each wavenumber bin. Our analysis returns a 2.7σ preference for an enhancement in the Lyα forest power spectrum at large scales, in excess of that expected for a spatially uniform ultraviolet background. This large-scale enhancement could be a signature of inhomogeneous reionization, although the statistical precision of these data is not yet sufficient for obtaining a robust detection of the relic post-reionization fluctuations. We show that future power spectrum measurements with relative uncertainties of ≲ 2.5 per cent should provide unambiguous evidence for an enhancement in the power spectrum on large scales