We present an effective model for the one-dimensional Lyman-$α$ flux power spectrum far above the baryonic Jeans scale. The main new ingredient is constituted by a set of two parameters that encode the impact of small, highly non-linear scales on the one-dimensional power spectrum on large scales, where it is measured by BOSS. We show that, by marginalizing over the model parameters that capture the impact of the intergalactic medium, the flux power spectrum from both simulations and observations can be described with high precision. The model displays a degeneracy between the neutrino masses and the (unknown, in our formalism) normalization of the flux power spectrum. This degeneracy can be lifted by calibrating one of the model parameters with simulation data, and using input from Planck CMB data. We demonstrate that this approach can be used to extract bounds on the sum of neutrino masses with comparably low numerical effort, while allowing for a conservative treatment of uncertainties from the dynamics of the intergalactic medium. An explorative analysis yields an upper bound of $0.16\,$eV at $95\%$ C.L. when applied to BOSS data at $3\leq z\leq 4.2$. We also forecast that if the systematic and statistical errors will be reduced by a factor two the upper bound will become $0.1\,$eV at $95\%$ C.L., and $0.056\,$eV when assuming a $1\%$ error.
Using cosmological particle hydrodynamical simulations and uniform ultraviolet backgrounds, we compare Lyman-$α$ forest flux spectra predicted by the conventional cold dark matter (CDM) model, the free-particle wave dark matter (FP$ψ$DM) model and extreme-axion wave dark matter (EA$ψ$DM) models of different initial axion field angles against the BOSS Lyman-$α$ forest absorption spectra with a fixed boson mass $m_b\sim 10^{-22}$eV. We recover results reported previously (Iršič et al. 2017b; Armengaud et al. 2017) that the CDM model agrees better with the BOSS data than the FP$ψ$DM model by a la…
We describe fitting methods developed to analyze fluctuations in the Lyman-α forest and measure the parameters of baryon acoustic oscillations (BAO). We apply our methods to BOSS Data Release 9. Our method is based on models of the three-dimensional correlation function in physical coordinate space, and includes the effects of redshift-space distortions, anisotropic non-linear broadening, and broadband distortions. We allow for independent scale factors along and perpendicular to the line of sight to minimize the dependence on our assumed fiducial cosmology and to obtain separate measurements …
Decaying Cold Dark Matter (DCDM) is a model that is currently under investigation regarding primarily the $S_8$ tension between cosmic microwave background (CMB) and certain large-scale structure measurements. The decay into one massive and one (or more) massless daughter particle(s) leads to a suppression of the power spectrum in the late universe that depends on the relative mass splitting $ε=(1-m^2/M^2)/2$ between the mother and massive daughter particle as well as the lifetime $τ$. In this work we investigate the impact of the BOSS DR14 one-dimensional Lyman-$α$ forest flux power spectrum …
We present the first measurement of the large-scale cross-correlation of Lyman alpha forest absorption and Damped Lyman alpha systems (DLA), using the 9th Data Release of the Baryon Oscillation Spectroscopic Survey (BOSS). The cross-correlation is clearly detected on scales up to 40 Mpc/h and is well fitted by the linear theory prediction of the standard Cold Dark Matter model of structure formation with the expected redshift distortions, confirming its origin in the gravitational evolution of structure. The amplitude of the DLA-Lyman alpha cross-correlation depends on only one free parameter,…
The Lyman-$α$ forest is a valuable probe of dark matter models featuring a scale-dependent suppression of the power spectrum as compared to $Λ$CDM. In this work, we present a new estimator of the Lyman-$α$ flux power spectrum that does not rely on hydrodynamical simulations. Our framework is characterized by nuisance parameters that encapsulate the complex physics of the intergalactic medium and sensitivity to highly non-linear small-scale modes. After validating the approach based on high-resolution hydrodynamical simulations for $Λ$CDM, we derive conservative constraints on interacting dark …
We measure the large-scale cross-correlation of quasars with the Lyman α forest absorption in redshift space, using ~ 60000 quasar spectra from Data Release 9 (DR9) of the Baryon Oscillation Spectroscopic Survey (BOSS). The cross-correlation is detected over a wide range of scales, up to comoving separations r of 80 Mpc/h. For r > 15 Mpc/h, we show that the cross-correlation is well fitted by the linear theory prediction for the mean overdensity around a quasar host halo in the standard ΛCDM model, with the redshift distortions indicative of gravitational evolution detected at high confidence.…
We investigate the large-scale structure of Lyman-alpha emission intensity in the Universe at redshifts z=2-3.5 using cross-correlation techniques. Our Lya emission samples are spectra of BOSS Luminous Red Galaxies from Data Release 12 with the best fit model galaxies subtracted. We cross-correlate the residual flux in these spectra with BOSS quasars, and detect a positive signal on scales 1-15 Mpc/h. We identify and remove a source of contamination not previously accounted for, due to the effects of quasar clustering on cross-fibre light. Corrected, our quasar-Lya emission cross-correlation i…
We present composite spectra constructed from a sample of 242,150 Lyman-alpha (Lya) forest absorbers at redshifts 2.4<z<3.1 identified in quasar spectra from the Baryon Oscillation Spectroscopic Survey (BOSS) as part of Data Release 9 of the Sloan Digital Sky Survey III. We select forest absorbers by their flux in bins 138 km/s wide (approximately the size of the BOSS resolution element). We split these absorbers into five samples spanning the range of flux -0.05 < F<0.45. Tests on a smaller sample of high-resolution spectra show that our three strongest absorption bins would probe circumgalac…
We present constraints on masses of active and sterile neutrinos. We use the one-dimensional Ly$α$-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$α$ 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$α$ powe…
Using a sample of approximately 14,000 z>2.1 quasars observed in the first year of the Baryon Oscillation Spectroscopic Survey (BOSS), we measure the three-dimensional correlation function of absorption in the Lyman-alpha forest. The angle-averaged correlation function of transmitted flux (F = exp(-tau)) is securely detected out to comoving separations of 60 Mpc/h, the first detection of flux correlations across widely separated sightlines. A quadrupole distortion of the redshift-space correlation function by peculiar velocities, the signature of the gravitational instability origin of structu…
The Baryon Oscillation Spectroscopic Survey (BOSS) has collected more than 150,000 $2.1 \leq z \leq 3.5$ quasar spectra since 2009. Using this unprecedented sample, we create a composite spectrum in the rest-frame of 102,150 quasar spectra from 800 Å to 3300 Å at a signal-to-noise ratio close to 1000 per pixel ($Δv$ of 69 km~s$^{-1}$). Included in this analysis is a correction to account for flux calibration residuals in the BOSS spectrophotometry. We determine the spectral index as a function of redshift of the full sample, warp the composite spectrum to match the median spectral index, and c…
In recent years, the autocorrelation of the hydrogen Lyman-α forest has been used to observe the baryon acoustic peak at redshift 2 < z < 3.5 using tens of thousands of QSO spectra from the BOSS survey. However, the interstellar medium of the Milky-Way introduces absorption lines into the spectrum of any extragalactic source. These lines, while weak and undetectable in a single BOSS spectrum, could potentially bias the cosmological signal. In order to examine this, we generate absorption line maps by stacking over a million spectra of galaxies and QSOs. We find that the systematics introduced …
We investigate the possibility of using the cross-correlation of the Lyman-alpha forest and redshifted 21-cm emission to detect the baryon acoustic oscillation (BAO). The standard Fisher matrix formalism is used to determine the accuracy with which it will be possible to measure cosmological distances using this signal. Earlier predictions indicate that it will be possible to measure the dilation factor D_V with 1.9 % accuracy at z=2.5 from the BOSS Lyman-alpha forest auto-correlation. In this paper we investigate if it is possible to improve the accuracy using the cross-correlation. We use a …
We present the BOSS Lyman-alpha (Lya) Forest Sample from SDSS Data Release 9, comprising 54,468 quasar spectra with zqso > 2.15 suitable for Lya forest analysis. This data set probes the intergalactic medium with absorption redshifts 2.0 < z_alpha < 5.7 over an area of 3275 square degrees, and encompasses an approximate comoving volume of 20 h^-3 Gpc^3. With each spectrum, we have included several products designed to aid in Lya forest analysis: improved sky masks that flag pixels where data may be unreliable, corrections for known biases in the pipeline estimated noise, masks for the cores of…
We measure the large-scale cross-correlation of quasars with the Lyman alpha forest absorption, using over 164,000 quasars from Data Release 11 of the SDSS-III Baryon Oscillation Spectroscopic Survey. We extend the previous study of roughly 60,000 quasars from Data Release 9 to larger separations, allowing a measurement of the Baryonic Acoustic Oscillation (BAO) scale along the line of sight $c/(H(z=2.36) ~ r_s) = 9.0 \pm 0.3$ and across the line of sight $D_A(z=2.36) / ~ r_s = 10.8 \pm 0.4$, consistent with CMB and other BAO data. Using the best fit value of the sound horizon from Planck data…
We present an analysis of high-resolution N-body simulations of decaying dark matter cosmologies focusing on the statistical properties of the transmitted Lyman-alpha forest flux in the high-redshift intergalactic medium. In this type of model a dark matter particle decays into a slightly less massive stable dark matter daughter particle and a comparably light particle. The small mass splitting provides a non-relativistic kick velocity V_k to the daughter particle resulting in free-streaming and subsequent damping of small-scale density fluctuations. Current Lyman-alpha forest power spectrum m…
Ratios of line of sight baryon acoustic oscillation (BAO) peaks at two redshifts only depend upon the average dark energy equation of states between those redshifts, as the dependence on anchors such as the BAO scale or the Hubble constant is canceled in a ratio. As a result, BAO ratios provide a probe of dark energy which is independent of both the cosmic distance ladder and the early evolution of universe. In this note, we use ratios to demonstrate that the known tension between the Lyman alpha forest BAO measurement and other probes arises entirely from recent (0.57<z<2.34) cosmological exp…
We use the Baryon Oscillation Spectroscopic Survey (BOSS) Data Release 9 (DR9) to detect and measure the position of the Baryonic Acoustic Oscillation (BAO) feature in the three-dimensional correlation function in the Lyman-alpha forest flux fluctuations at a redshift z=2.4. The feature is clearly detected at significance between 3 and 5 sigma (depending on the broadband model and method of error covariance matrix estimation) and is consistent with predictions of the standard LCDM model. We assess the biases in our method, stability of the error covariance matrix and possible systematic effect…
The imprint of Baryonic Acoustic Oscillations (BAO) on the matter power spectrum can be constrained using the neutral hydrogen density in the intergalactic medium as a tracer of the matter density. One of the goals of the Baryon Oscillation Spectroscopic Survey (BOSS) of the Sloan Digital Sky Survey (SDSS-III) is to derive the Hubble expansion rate and the angular scale from the BAO signal in the IGM. To this aim, the Lyman-alpha forest of 10^5 quasars will be observed in the redshift range 2.2<z<3.5 and over 10,000 deg^2. We simulated the BOSS QSO survey to estimate the statistical accuracy o…
With recent Lyman-alpha forest data from BOSS and XQ-100, some studies suggested that the lower mass limit on the fuzzy dark matter (FDM) particles is lifted up to $10^{-21}\,\mathrm{eV}$. However, such a limit was obtained by $Λ$CDM simulations with the FDM initial condition and the quantum pressure (QP) was not taken into account which could have generated non-trivial effects in large scales structures. We investigate the QP effects in cosmological simulations systematically, and find that the QP leads to further suppression of the matter power spectrum at small scales, as well as the halo m…
The Lyman-$β$ forest refers to a region in the spectra of distant quasars that lies between the rest-frame Lyman-$β$ and Lyman-$γ$ emissions. The forest in this region is dominated by a combination of absorption due to resonant Ly$α$ and Ly$β$ scattering. When considering the 1D Ly$β$ forest in addition to the 1D Ly$α$ forest, the full statistical description of the data requires four 1D power spectra: Ly$α$ and Ly$β$ auto-power spectra and the Ly$α$-Ly$β$ real and imaginary cross-power spectra. We describe how these can be measured using an optimal quadratic estimator that naturally disentang…
Current analyses of the Lyman-alpha forest assume that the primordial power spectrum of density perturbations obeys a simple power law, a strong theoretical assumption which should be tested. Employing a large suite of numerical simulations which drop this assumption, we reconstruct the shape of the primordial power spectrum using Lyman-alpha data from the Sloan Digital Sky Survey (SDSS). Our method combines a minimally parametric framework with cross-validation, a technique used to avoid over-fitting the data. Future work will involve predictions for the upcoming Baryon Oscillation Sky Survey…
Maps of the large-scale structure of the Universe at redshifts 2-4 can be made with the Lyman-alpha forest which are complementary to low redshift galaxy surveys. We apply the Wiener interpolation method of Caucci et al. to construct three-dimensional maps from sets of Lyman-alpha forest spectra taken from cosmological hydrodynamic simulations. We mimic some current and future quasar redshift surveys (BOSS, eBOSS and MS-DESI) by choosing similar sightline densities. We use these appropriate subsets of the Lyman-alpha absorption sightlines to reconstruct the full three dimensional Lyman-alpha f…
The quest for the neutrino mass is a central goal in contemporary cosmology, subject to intense scrutiny, and among different large-scale structure tracers the Lyman-Alpha forest is re-emerging as a unique tool to probe the neutrino mass at high-redshift - through characteristic imprints on the transmitted Lyman-Alpha flux. A detailed modeling of the low-density regions of the intergalactic medium in presence of massive neutrinos on scale ranging from a few to hundreds of megaparsecs is required, if one wants to interpret state-of-the-art data from observations of quasar spectra. To this end, …
It appears inevitable that reionization processes would have produced large-scale temperature fluctuations in the intergalactic medium. Using toy temperature models and detailed heating histories from cosmological simulations of HeII reionization, we study the consequences of inhomogeneous heating for the Ly-alpha forest. The impact of temperature fluctuations in physically well-motivated models can be surprisingly subtle. In fact, we show that temperature fluctuations at the level predicted by our reionization simulations do not give rise to detectable signatures in the types of statistics th…
We describe mock data-sets generated to simulate the high-redshift quasar sample in Data Release 11 (DR11) of the SDSS-III Baryon Oscillation Spectroscopic Survey (BOSS). The mock spectra contain Lyα forest correlations useful for studying the 3D correlation function including Baryon Acoustic Oscillations (BAO). They also include astrophysical effects such as quasar continuum diversity and high-density absorbers, instrumental effects such as noise and spectral resolution, as well as imperfections introduced by the SDSS pipeline treatment of the raw data. The Lyα forest BAO analysis of the BOSS…
We use the Ly-$α$ Mass Association Scheme (LyMAS; Peirani et al. 2014) to predict cross-correlations at $z=2.5$ between dark matter halos and transmitted flux in the Ly-$α$ forest, and compare to cross-correlations measured for quasars and damped Ly-$α$ systems (DLAs) from the Baryon Oscillation Spectroscopic Survey (BOSS) by Font-Ribera et al. (2012, 2013). We calibrate LyMAS using Horizon-AGN hydrodynamical cosmological simulations of a $(100\ h^{-1}\ \mathrm{Mpc})^3$ comoving volume. We apply this calibration to a $(1\ h^{-1}\ \mathrm{Gpc})^3$ simulation realized with $2048^3$ dark matter p…
Visualizing the high-redshift Universe is difficult due to the dearth of available data; however, the Lyman-alpha forest provides a means to map the intergalactic medium at redshifts not accessible to large galaxy surveys. Large-scale structure surveys, such as the Baryon Oscillation Spectroscopic Survey (BOSS), have collected quasar (QSO) spectra that enable the reconstruction of HI density fluctuations. The data fall on a collection of lines defined by the lines-of-sight (LOS) of the QSO, and a major issue with producing a 3D reconstruction is determining how to model the regions between the…
(Abridged) We detect the large-scale structure of Lya emission in the Universe at redshifts z=2-3.5 by measuring the cross-correlation of Lya surface brightness with quasars in SDSS/BOSS. We use a million spectra targeting Luminous Red Galaxies at z<0.8, after subtracting a best fit model galaxy spectrum from each one, as an estimate of the high-redshift Lya surface brightness. The quasar-Lya emission cross-correlation we detect has a shape consistent with a LambdaCDM model with Omega_M =0.30^+0.10-0.07. The predicted amplitude of this cross-correlation is proportional to the product of the me…
[abridged] We describe LyMAS (Ly-alpha Mass Association Scheme), a method of predicting clustering statistics in the Ly-alpha forest on large scales from moderate resolution simulations of the dark matter distribution, with calibration from high-resolution hydrodynamic simulations of smaller volumes. We use the "Horizon MareNostrum" simulation, a 50 Mpc/h comoving volume evolved with the adaptive mesh hydrodynamic code RAMSES, to compute the conditional probability distribution P(F_s|delta_s) of the transmitted flux F_s, smoothed (1-dimensionally) over the spectral resolution scale, on the dar…
We present the Lyman-$α$ 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. T…
We present the first detection of a correlation between the Lyman-$α$ forest and cosmic microwave background (CMB) lensing. For each Lyman-$α$ forest in SDSS-III/BOSS DR12, we correlate the one-dimensional power spectrum with the CMB lensing convergence on the same line of sight from Planck. This measurement constitutes a position-dependent power spectrum, or a squeezed bispectrum, and quantifies the non-linear response of the Lyman-$α$ forest power spectrum to a large-scale overdensity. The signal is measured at 5~$σ$ and is consistent with the $Λ$CDM expectation. We measure the linear bias o…
Massive spectroscopic surveys of high-redshift quasars yield large numbers of correlated Lyman α absorption spectra that can be used to measure large-scale structure. Simulations of these surveys are required to accurately interpret the measurements of correlations and correct for systematic errors. An efficient method to generate mock realizations of Lyman α forest surveys is presented which generates a field over the lines of sight to the survey sources only, instead of having to generate it over the entire three-dimensional volume of the survey. The method can be calibrated to reproduce the…
We use subhalo abundance matching (SHAM) to model the stellar mass function (SMF) and clustering of the Baryon Oscillation Spectroscopic Survey (BOSS) "CMASS" sample at $z\sim0.5$. We introduce a novel method which accounts for the stellar mass incompleteness of CMASS as a function of redshift, and produce CMASS mock catalogs which include selection effects, reproduce the overall SMF, the projected two-point correlation function $w_{\rm p}$, the CMASS $dn/dz$, and are made publicly available. We study the effects of assembly bias above collapse mass in the context of "age matching" and show th…
Even though the Hubble constant cannot be significantly determined by the low-redshift Baryon Acoustic Oscillation (BAO) data alone, it can be tightly constrained once the high-redshift BAO data are combined. Combining BAO data from 6dFGS, BOSS DR11 clustering of galaxies, WiggleZ and $z=2.34$ from BOSS DR11 quasar Lyman-$α$ forest lines, we get $H_0=68.17^{+1.55}_{-1.56}$ km s$^{-1}$ Mpc$^{-1}$. In addition, adopting the the simultaneous measurements of $H(z)$ and $D_A(z)$ from the two-dimensional two-point correlation function from BOSS DR9 CMASS sample and two-dimensional matter power spect…
Current results from the Lyman alpha forest assume that the primordial power spectrum of density perturbations follows a simple power law form, with running. We present the first analysis of Lyman alpha data to study the effect of relaxing this strong assumption on primordial and astrophysical constraints. We perform a large suite of numerical simulations, using them to calibrate a minimally parametric framework for describing the power spectrum. Combined with cross-validation, a statistical technique which prevents over-fitting of the data, this framework allows us to reconstruct the power sp…
We expect a detectable correlation between two seemingly unrelated quantities: the four point function of the cosmic microwave background (CMB) and the amplitude of flux decrements in quasar (QSO) spectra. The amplitude of CMB convergence in a given direction measures the projected surface density of matter. Measurements of QSO flux decrements trace the small-scale distribution of gas along a given line-of-sight. While the cross-correlation between these two measurements is small for a single line-of-sight, upcoming large surveys should enable its detection. This paper presents analytical esti…
The Ly$α$ forest transmission probability distribution function (PDF) is an established probe of the intergalactic medium (IGM) astrophysics, especially the temperature-density relationship of the IGM. We measure the transmission PDF from 3393 Baryon Oscillations Spectroscopic Survey (BOSS) quasars from SDSS Data Release 9, and compare with mock spectra that include careful modeling of the noise, continuum, and astrophysical uncertainties. The BOSS transmission PDFs, measured at $\langle z \rangle = [2.3,2.6,3.0]$, are compared with PDFs created from mock spectra drawn from a suite of hydrodyn…
The result presented by the BOSS-SDSS Collaboration measuring the baryon acoustic oscillations of the Lyman-$α$ forest from high-redshift quasars indicates a $2.5σ$ departure from the standard $Λ$-cold-dark-matter model. This is the first time that the evolution of dark energy at high redshifts has been measured, and the current results cannot be explained by simple generalizations of the cosmological constant. We show here that a simple phenomenological interaction in the dark sector provides a good explanation for this deviation, naturally accommodating the Hubble parameter obtained by BOSS,…
We present methods for interpolating between the 1-D flux power spectrum of the Lyman-$α$ forest, as output by cosmological hydrodynamic simulations. Interpolation is necessary for cosmological parameter estimation due to the limited number of simulations possible. We construct an emulator for the Lyman-$α$ forest flux power spectrum from $21$ small simulations using Latin hypercube sampling and Gaussian process interpolation. We show that this emulator has a typical accuracy of 1.5% and a worst-case accuracy of 4%, which compares well to the current statistical error of 3 - 5% at $z < 3$ from…
We present a suite of cosmological N-body simulations with cold dark matter and baryons aiming at modeling the low-density regions of the IGM as probed by the Lyman-$α$ forests at high redshift. The simulations are designed to match the requirements imposed by the quality of BOSS and eBOSS data. They are made using either 2x768$^3$ or 2x192$^3$ particles, spanning volumes ranging from (25 Mpc.h$^{-1})^3$ for high-resolution simulations to (100 Mpc.h$^{-1})^3$ for large-volume ones. Using a splicing technique, the resolution is further enhanced to reach the equivalent of simulations with 2x3072…
The forest of Lyman-alpha absorption lines seen in the spectra of distant quasars has become an important probe of the distribution of matter in the Universe. We use large, hydrodynamical simulations from the OWLS project to investigate the effect of feedback from galaxy formation on the probability distribution function and the power spectrum of the Lyman-alpha transmitted flux. While metal-line cooling is unimportant, both galactic outflows from massive galaxies driven by active galactic nuclei and winds from low-mass galaxies driven by supernovae have a substantial impact on the flux statis…
Cosmological hydrodynamic simulations can accurately predict the properties of the intergalactic medium (IGM), but only under the condition of retaining high spatial resolution necessary to resolve density fluctuations in the IGM. This resolution constraint prohibits simulating large volumes, such as those probed by BOSS and future surveys, like DESI and 4MOST. To overcome this limitation, we present Iteratively Matched Statistics (IMS), a novel method to accurately model the Lyman-alpha forest with collisionless N-body simulations, where the relevant density fluctuations are unresolved. We us…
Continuum fitting is an important aspect of Lyman-alpha forest science, since errors in the estimated optical depths scale with the fractional continuum error. However, traditional methods of estimating continua in noisy and moderate-resolution spectra (S/N < 10 pixel^-1 and R ~ 2000, respectively, such as SDSS) using power-law extrapolation or the mean spectrum, achieve no better than ~ 10-15% RMS accuracy. To improve on this, we introduce mean-flux regulated/principal component analysis (MF-PCA) continuum fitting. In this technique, PCA fitting is carried out redwards of the quasar Lyman-alp…
We present constraints on neutrino masses, the primordial fluctuation spectrum from inflation, and other parameters of the $Λ$CDM model, using the one-dimensional Ly$α$-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 f…
The Baryon Oscillation Spectroscopic Survey of SDSS-III has provided an unprecedentedly large sample of Damped \lya systems (DLAs), the largest repositories of neutral hydrogen in the Universe. This DLA sample has been used to determine the DLA bias factor from their cross-correlation with the \lya forest absorption in \cite{FontRibera2012,Perez2018}, showing that DLAs are associated with relatively massive halos. However, the low resolution and signal-to-noise of BOSS spectra do not allow precise measurements of the DLA metal lines. We define a metal strength parameter, $S$, based on combinin…
We report the first test of isotropy of the Universe in the matter dominated epoch using the Lyman-$α$ forest data from the high redshift quasars ($z>2$) from SDSS-III BOSS-DR9 datasets. Using some specified data cuts, we obtain the probability distribution function (PDF) of the Lyman-$α$ forest transmitted flux and use the statistical moments of the PDF to address the isotropy of the Universe. In an isotropic Universe one would expect the transmitted flux to have consistent statistical characteristics in different parts of the sky. We trisect the total survey area of 3275 ${\rm deg}^2$ along …
If a significant fraction of the dark matter in the Universe is made of an ultra-light scalar field, named fuzzy dark matter (FDM) with a mass $m_a$ of the order of $10^{-22}-10^{-21}$ eV, then its de Broglie wavelength is large enough to impact the physics of large scale structure formation. In particular, the associated cut-off in the linear matter power spectrum modifies the structure of the intergalactic medium (IGM) at the scales probed by the Lyman-$α$ forest of distant quasars. We study this effect by making use of dedicated cosmological simulations which take into account the hydrodyna…
The free-streaming of keV-scale particles impacts structure growth on scales that are probed by the Lyman-alpha forest of distant quasars. Using an unprecedentedly large sample of medium-resolution QSO spectra from the ninth data release of SDSS, along with a state-of-the-art set of hydrodynamical simulations to model the Lyman-alpha forest in the non-linear regime, we issue one of the tightest bounds to date, from Ly-$α$ data alone, on pure dark matter particles : $m_X > 4.09 \: \rm{keV}$ (95% CL) for early decoupled thermal relics such as a hypothetical gravitino, and correspondingly $m_s > …
Cosmological hydrodynamic simulations predict the physical state of baryons in the circumgalactic medium (CGM), which can be directly tested via quasar absorption line observations. We use high resolution "zoom-in" simulations of 21 galaxies to characterize the distribution of neutral hydrogen around halos in the mass range M_vir~ 2x10^11 - 4x10^12 M_sun at z~2. We find that both the mass fraction of cool (T <= 3x10^4 K) gas and the covering fraction of optically-thick Lyman limit systems (LLSs) depend only weakly on halo mass, even around the critical value for the formation of stable virial …
The neutral intergalactic medium in the post reionization epoch allows us to study cosmological structure formation through the observation of the redshifted 21 cm signal and the Lyman-alpha forest. We investigate the possibility of measuring the total neutrino mass through the suppression of power in the matter power spectrum. We investigate the possibility of measuring the neutrino mass through its imprint on the cross-correlation power spectrum of the 21-cm signal and the Lyman-alpha forest. We consider a radio-interferometric measurement of the 21 cm signal with a SKA1-mid like radio teles…
The Lyman alpha forest power spectrum has been measured on large scales by the BOSS survey in SDSS-III at $z\sim 2.3$, has been shown to agree well with linear theory predictions, and has provided the first measurement of Baryon Acoustic Oscillations at this redshift. However, the power at small scales, affected by non-linearities, has not been well examined so far. We present results from a variety of hydrodynamic simulations to predict the redshift space non-linear power spectrum of the Lyman Alpha transmission for several models, testing the dependence on resolution and box size. A new fitt…
A 2.5-3 sigma discrepancy has been reported between the baryonic acoustic oscillation peak (BAO) in the Lyman $α$ forest at $z\sim 2.34$ and the best fit Planck $Λ$CDM cosmology. To isolate the origin of the tension, we consider unanchored BAO, in which the standard BAO ruler is not calibrated, eliminating any dependence on cosmology before redshift $z\sim 2.34$. We consider BOSS BAO measurements at $z\sim 0.32$, 0.57 and 2.34, using the full 2-dimensional constraints on the angular and line of sight BAO scale, as well as isotropic BAO measurements by 6dF and SDSS at $z\sim 0.106$ and $z\sim 0…
The generalized Chaplygin gas cosmology provides a prime example for the class of unified dark matter models, which substitute the two dark components of the standard cosmological LCDM concordance model by a single dark component. The equation of state of the generalized Chaplygin gas is characterised by a parameter alpha such that the standard LCDM model is recovered in the case alpha=0 with respect to the background dynamics and the cosmic microwave background (CMB) statistics. This allows to investigate the concordance of different cosmological data sets with respect to alpha. We compare th…
We present a measurement of the DLA mean bias from the cross-correlation of DLA and the Ly$α$ forest, updating earlier results of Font-Ribera et al. 2012 with the final BOSS Data Release and an improved method to address continuum fitting corrections. Our cross-correlation is well fitted by linear theory with the standard $ΛCDM$ model, with a DLA bias of $b_{\rm DLA} = 1.99\pm 0.11$; a more conservative analysis, which removes DLA in the Ly$β$ forest and uses only the cross-correlation at $r> 10{\rm h^{-1}\,Mpc}$, yields $b_{\rm DLA} = 2.00\pm 0.19$. This assumes the cosmological model from \c…
