arXiv subjects

L. Moscardini

Publications and source records attributed to L. Moscardini.

At least 199 records · Page 11Linked to original sources

arXiv2013

The VIMOS Public Extragalactic Redshift Survey (VIPERS). An unprecedented view of galaxies and large-scale structure at 0.5<z<1.2

We describe the construction and general features of VIPERS, the VIMOS Public Extragalactic Redshift Survey. This `Large Programme' has been using the ESO VLT with the aim of building a spectroscopic sample of ~100,000 galaxies with i_{AB}<22.5 and 0.5<z<1.5. The survey covers a total area of ~24 deg^2 within the CFHTLS-Wide W1 and W4 fields. VIPERS is designed to address a broad range of problems in large-scale structure and galaxy evolution, thanks to a unique combination of volume (~ 5 x 10^7 h^{-3} Mpc^3) and sampling rate (~ 40%), comparable to state-of-the-art surveys of the local Universe, together with extensive multi-band optical and near-infrared photometry. Here we present the survey design, the selection of the source catalogue and the development of the spectroscopic observations. We discuss in detail the overall selection function that results from the combination of the different constituents of the project. This includes the masks arising from the parent photometric sample and the spectroscopic instrumental footprint, together with the weights needed to account for the sampling and the success rates of the observations. Using the catalogue of 53,608 galaxy redshifts composing the forthcoming VIPERS Public Data Release 1 (PDR-1), we provide a first assessment of the quality of the spectroscopic data. Benefiting from the combination of size and detailed sampling of this dataset, we conclude by presenting a map showing in unprecedented detail the large-scale distribution of galaxies between 5 and 8 billion years ago. [abridged]

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arXiv2013

A numerical study of the effects of primordial non-Gaussianities on weak lensing statistics

While usually cosmological initial conditions are assumed to be Gaussian, inflationary theories can predict a certain amount of primordial non-Gaussianity which can have an impact on the statistical properties of the lensing observables. In order to evaluate this effect, we build a large set of realistic maps of different lensing quantities starting from light-cones extracted from large dark-matter only N-body simulations with initial conditions corresponding to different levels of primordial local non-Gaussianity strength $f_{\rm NL}$. Considering various statistical quantities (PDF, power spectrum, shear in aperture, skewness and bispectrum) we find that the effect produced by the presence of primordial non-Gaussianity is relatively small, being of the order of few per cent for values of $|f_{\rm NL}|$ compatible with the present CMB constraints and reaching at most 10-15 per cent for the most extreme cases with $|f_{\rm NL}|=1000$. We also discuss the degeneracy of this effect with the uncertainties due to the power spectrum normalization $σ_8$ and matter density parameter $Ω_{\rm m}$, finding that an error in the determination of $σ_8$ ($Ω_{\rm m}$) of about 3 (10) per cent gives differences comparable with non-Gaussian models having $f_{\rm NL}=\pm 1000$. These results suggest that the possible presence of an amount of primordial non-Gaussianity corresponding to $|f_{\rm NL}|=100$ is not hampering a robust determination of the main cosmological parameters in present and future weak lensing surveys, while a positive detection of deviations from the Gaussian hypothesis is possible only breaking the degeneracy with other cosmological parameters and using data from deep surveys covering a large fraction of the sky.

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arXiv2013

Structure formation in cosmologies with oscillating dark energy

{abridged} We study the imprints on the formation and evolution of cosmic structures of dynamical dark energy models, characterized by an oscillating equation of state. The redshift evolution of the equation of state parameter w(z) for dark energy is characterized by two parameters, describing the amplitude and the frequency of the oscillations. We consider six different oscillating dark energy models, each characterized by a different set of parameter values. Under the common assumption that dark energy is not clustering on the scales of interest, we study different aspects of cosmic structure formation. In particular, we self-consistently solve the spherical collapse problem. We then estimate the behavior of several cosmological observables, such as the linear growth factor, the Integrated Sachs-Wolfe (ISW) effect, the number counts of massive structures, and the matter and cosmic shear power spectra. We show that, independently of the amplitude and the frequency of the dark energy oscillations, none of the aforementioned observables show an oscillating behavior as a function of redshift. This is a consequence of the said observables' being integrals over some functions of the expansion rate over cosmic history. We also notice that deviations with respect to the expectations for a fiducial LambdaCDM cosmology are generically small, and in the majority of the cases distinguishing an oscillating dark energy model would be difficult. Exceptions to this conclusion are provided by the cosmic shear power spectrum, which for some of the models shows a difference at the level of \sim 10% over a wide range of angular scales, and the abundance of galaxy clusters, which is modified at the $\sim 10-20%$ level at $z \gtrsim 0.6$ for future wide weak lensing surveys.

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arXiv2012

The VIMOS Public Extragalactic Redshift Survey (VIPERS): spectral classification through Principal Component Analysis

We develop a Principal Component Analysis aimed at classifying a sub-set of 27,350 spectra of galaxies in the range 0.4 < z < 1.0 collected by the VIMOS Public Extragalactic Redshift Survey (VIPERS). We apply an iterative algorithm to simultaneously repair parts of spectra affected by noise and/or sky residuals, and reconstruct gaps due to rest-frame transformation, and obtain a set of orthogonal spectral templates that span the diversity of galaxy types. By taking the three most significant components, we find that we can describe the whole sample without contamination from noise. We produce a catalogue of eigen-coefficients and template spectra that will be part of future VIPERS data releases. Our templates effectively condense the spectral information into two coefficients that can be related to the age and star formation rate of the galaxies. We examine the spectrophotometric types in this space and identify early, intermediate, late and starburst galaxies.

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arXiv2012

Constraining Primordial Magnetic Fields with Future Cosmic Shear Surveys

The origin of astrophysical magnetic fields observed in galaxies and clusters of galaxies is still unclear. One possibility is that primordial magnetic fields generated in the early Universe provide seeds that grow through compression and turbulence during structure formation. A cosmological magnetic field present prior to recombination would produce substantial matter clustering at intermediate/small scales, on top of the standard inflationary power spectrum. In this work we study the effect of this alteration on one particular cosmological observable, cosmic shear. We adopt the semi-analytic halo model in order to describe the non-linear clustering of matter, and feed it with the altered mass variance induced by primordial magnetic fields. We find that the convergence power spectrum is, as expected, substantially enhanced at intermediate/small angular scales, with the exact amplitude of the enhancement depending on the magnitude and power-law index of the magnetic field power spectrum. We use the predicted statistical errors for a future wide-field cosmic shear survey, on the model of the ESA Cosmic Vision mission \emph{Euclid}, in order to forecast constraints on the amplitude of primordial magnetic fields as a function of the spectral index. We find that the amplitude will be constrained at the level of $\sim 0.1$ nG for $n_B\sim -3$, and at the level of $\sim 10^{-7}$ nG for $n_B\sim 3$. The latter is at the same level of lower bounds coming from the secondary emission of gamma-ray sources, implying that for high spectral indices \emph{Euclid} will certainly be able to detect primordial magnetic fields, if they exist. The present study shows how large-scale structure surveys can be used for both understanding the origins of astrophysical magnetic fields and shedding new light on the physics of the pre-recombination Universe. (abridged)

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arXiv2012

Constraining primordial non-Gaussianity with cosmological weak lensing: shear and flexion

We examine the cosmological constraining power of future large-scale weak lensing surveys on the model of \emph{Euclid}, with particular reference to primordial non-Gaussianity. Our analysis considers several different estimators of the projected matter power spectrum, based on both shear and flexion, for which we review the covariances and Fisher matrices. The bounds provided by cosmic shear alone for the local bispectrum shape, marginalized over $σ_8$, are at the level of $Δf_\mathrm{NL} \sim 100$. We consider three additional bispectrum shapes, for which the cosmic shear constraints range from $Δf_\mathrm{NL}\sim 340$ (equilateral shape) up to $Δf_\mathrm{NL}\sim 500$ (orthogonal shape). The competitiveness of cosmic flexion constraints against cosmic shear ones depends on the galaxy intrinsic flexion noise, that is still virtually unconstrained. Adopting the very high value that has been occasionally used in the literature results in the flexion contribution being basically negligible with respect to the shear one, and for realistic configurations the former does not improve significantly the constraining power of the latter. Since the flexion noise decreases with decreasing scale, by extending the analysis up to $\ell_\mathrm{max} = 20,000$ cosmic flexion, while being still subdominant, improves the shear constraints by $\sim 10%$ when added. However on such small scales the highly non-linear clustering of matter and the impact of baryonic physics make any error estimation uncertain. By considering lower, and possibly more realistic, values of the flexion intrinsic shape noise results in flexion constraining power being a factor of $\sim 2$ better than that of shear, and the bounds on $σ_8$ and $f_\mathrm{NL}$ being improved by a factor of $\sim 3$ upon their combination. (abridged)

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arXiv2012

The effect of feedback on the emission properties of the Warm-Hot Intergalactic Medium

At present, 30-40 per cent of the baryons in the local Universe is still undetected. According to theoretical predictions, this gas should reside in filaments filling the large-scale structure (LSS) in the form of a Warm-Hot Intergalactic Medium (WHIM), at temperatures of 10^5 - 10^7 K, thus emitting in the soft X-ray energies via free-free interaction and line emission from heavy elements. In this work we characterize the properties of the X-ray emission of the WHIM, and the LSS in general, focusing on the influence of different physical mechanisms, namely galactic winds (GWs), black-hole feedback and star-formation, and providing estimates of possible observational constraints. To this purpose we use a set of cosmological hydrodynamical simulations that include a self-consistent treatment of star-formation and chemical enrichment of the intergalactic medium, that allows us to follow the evolution of different metal species. We construct a set of simulated light-cones to make predictions of the emission in the 0.3-10 keV energy range. We obtain that GWs increase by a factor of 2 the emission of both galaxy clusters and WHIM. The amount of oxygen at average temperature and, consequently, the amount of expected bright Ovii and Oviii lines is increased by a factor of 3 due to GWs and by 20 per cent when assuming a top-heavy IMF. We compare our results with current observational constraints and find that the emission from faint groups and WHIM should account from half to all of the unresolved X-ray background in the 1-2 keV band.

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arXiv2011

Euclid Definition Study Report

Euclid is a space-based survey mission from the European Space Agency designed to understand the origin of the Universe's accelerating expansion. It will use cosmological probes to investigate the nature of dark energy, dark matter and gravity by tracking their observational signatures on the geometry of the universe and on the cosmic history of structure formation. The mission is optimised for two independent primary cosmological probes: Weak gravitational Lensing (WL) and Baryonic Acoustic Oscillations (BAO). The Euclid payload consists of a 1.2 m Korsch telescope designed to provide a large field of view. It carries two instruments with a common field-of-view of ~0.54 deg2: the visual imager (VIS) and the near infrared instrument (NISP) which contains a slitless spectrometer and a three bands photometer. The Euclid wide survey will cover 15,000 deg2 of the extragalactic sky and is complemented by two 20 deg2 deep fields. For WL, Euclid measures the shapes of 30-40 resolved galaxies per arcmin2 in one broad visible R+I+Z band (550-920 nm). The photometric redshifts for these galaxies reach a precision of dz/(1+z) < 0.05. They are derived from three additional Euclid NIR bands (Y, J, H in the range 0.92-2.0 micron), complemented by ground based photometry in visible bands derived from public data or through engaged collaborations. The BAO are determined from a spectroscopic survey with a redshift accuracy dz/(1+z) =0.001. The slitless spectrometer, with spectral resolution ~250, predominantly detects Ha emission line galaxies. Euclid is a Medium Class mission of the ESA Cosmic Vision 2015-2025 programme, with a foreseen launch date in 2019. This report (also known as the Euclid Red Book) describes the outcome of the Phase A study.

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arXiv2011

Matter power spectra in dynamical-Dark Energy cosmologies

(abridged) We used a suite of numerical cosmological simulations in order to investigate the effect of gas cooling and star formation on the large scale matter distribution. The simulations follow the formation of cosmic structures in five different Dark Energy models: the fiducial $Λ$CDM cosmology and four models where the Dark Energy density is allowed to have a non-trivial redshift evolution. For each cosmology we have a control run with dark matter only, in order to allow a direct assessment of the impact of baryonic processes. We found that the power spectra of gas and stars, as well as the total matter power spectrum, are in qualitative agreement with the results of previous works in the framework of the fiducial model, although several quantitative differences exist. We used the halo model in order to investigate the backreaction of gas and stars on the dark matter distribution, finding that it is very well reproduced by increasing the average dark matter halo concentration by 17%, irrespective of the mass. Moving to model universes dominated by dynamical Dark Energy, it turns out that they introduce a specific signature on the power spectra of the various matter components, that is qualitatively independent of the exact cosmology considered. This generic shape is well captured by the halo model, however the finer details of the dark matter power spectrum can be precisely captured only at the cost of a few slight modifications to the ingredients entering the model. The backreaction of baryons onto the dark matter distribution works pretty much in the same way as in the reference $Λ$CDM model. Nonetheless, the increment in average concentration is less pronounced than in the fiducial model (only $\sim 10%$), in agreement with a series of other clues pointing toward the fact that star formation is less efficient when Dark Energy displays a dynamical evolution.

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arXiv2011

On a novel approach using massive clusters at high redshifts as cosmological probe

In this work we propose a novel method for testing the validity of the fiducial LCDM cosmology by measuring the cumulative distribution function of the most massive haloes in a sample of subvolumes of identical size tiled on the sky at a fixed redshift. The fact that the most massive clusters probe the high-mass tail of the mass function, where the difference between LCDM and alternative cosmological models is strongest, makes our method particularly interesting as a cosmological probe. We utilise general extreme value statistics (GEV) to obtain a cumulative distribution function of the most massive objects in a given volume. We sample this distribution function according to the number of patches covered by the survey area for a range of different "test cosmologies" and for differently accurate mass estimations of the haloes. By fitting this sample with the GEV distribution function, we can study which parameters are the most sensitive with respect to the test cosmologies. We find that the peak of the probability distribution function of the most massive halo is well suited to test the validity of the fiducial LCDM model, once we are able to establish a sufficiently complete large-area survey with M_lim=10^14.5 M_sun/h (M_lim=10^14 M_sun/h) at redshifts above z=1 (z=1.5). Being of cumulative nature the proposed measure is robust and an accuracy of 20-30% in the cluster masses would be sufficient to test for alternative models. Since one only needs the most massive system in each angular patch, this method would be ideally suited as a first fast consistency check before going into a more complex statistical analysis of the observed halo sample.

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arXiv2011

The effect of primordial non-Gaussianity on the skeleton of cosmic shear maps

(abridged) We explore the imprints of deviations from Gaussian primordial density fluctuations on the skeleton of the large-scale matter distribution as mapped through cosmological weak lensing. We computed the skeleton length of simulated effective convergence maps covering $\sim 35$ sq. deg each, extracted from a suite of cosmological $n-$body runs with different levels of local primordial non-Gaussianity. The latter is expected to alter the structure formation process with respect to the fiducial Gaussian scenario, and thus to leave a signature on the cosmic web. We found that alterations of the initial conditions consistently modify both the cumulative and the differential skeleton length, although the effect is generically smaller than the cosmic variance and depends on the smoothing of the map prior to the skeleton computation. Nevertheless, the qualitative shape of these deviations is rather similar to their primordial counterparts, implying that skeleton statistics retain good memory of the initial conditions. We performed a statistical analysis in order to find out at what Confidence Level primordial non-Gaussianity could be constrained by the skeleton test on cosmic shear maps of the size we adopted. At 68.3% Confidence Level we found an error on the measured level of primordial non-Gaussianity of $Δf_\mathrm{NL}\sim 300$, while at 90% Confidence Level it is of $Δf_\mathrm{NL}\sim 500$. While these values by themselves are not competitive with the current constraints, weak lensing maps larger than those used here would have a smaller field-to-field variance, and thus would likely lead to tighter constraints. A rough estimate indicates $Δf_\mathrm{NL} \sim$ a few tens at 68.3% Confidence Level for an all-sky weak lensing survey.

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arXiv2011

Abell 611. II. X-ray and strong lensing analyses

We present the results of our analyses of the X-ray emission and of the strong lensing systems in the relaxed galaxy cluster Abell 611 (z=0.288). We infer the X-ray mass estimate deriving the density and temperature profiles of the intra-cluster medium within the radius r ~ 700 kpc through a non-parametric approach; assuming that the cluster is in hydrostatic equilibrium and adopting a matter density profile, we can recover the total mass distribution of Abell 611 via the X-ray data. We derive the total projected mass in the central region of Abell 611 performing a parametric analysis of its strong lensing features through the publicly available analysis software Lenstool. As a final step we compare the results obtained with both methods. We derive a good agreement between the X-ray and strong lensing total mass estimates in the central region (i.e. within the radius r ~100 kpc), while a marginal disagreement is found between the two mass estimates when extrapolating the strong lensing results in the outer spatial range. We suggest that in this case the X-ray/strong lensing mass disagreement can be explained by an incorrect estimate of the relative contributions of the baryonic component and of the dark matter, caused by the intrinsic degeneracy between the different mass components in the strong lensing analysis. We discuss the effect of some possible systematic errors that influence both mass estimates. We find a slight dependence of the measurements of the X-ray temperatures (and therefore of the X-ray total masses) on the background adopted in the spectral analysis, with total deviations on the value of M_200 of the order of the 1-sigma statistical error. The strong lensing mass results are instead sensitive to the parameterisation of the galactic halo mass in the central regions, in particular to the modelling of the Brightest Cluster Galaxy (BCG) baryonic component.

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arXiv2011

Comparison of an X-ray selected sample of massive lensing clusters with the MareNostrum Universe LCDM simulation

A long-standing problem of strong lensing by galaxy clusters regards the observed high rate of giant gravitational arcs as compared to the predictions in the framework of the "standard" cosmological model. Recently, few other inconsistencies between theoretical expectations and observations have been claimed which regard the large size of the Einstein rings and the high concentrations of few clusters with strong lensing features. All of these problems consistently indicate that observed galaxy clusters may be gravitational lenses stronger than expected. We use clusters extracted from the MareNostrum Universe to build up mock catalogs of galaxy clusters selected through their X-ray flux. We use these objects to estimate the probability distributions of lensing cross sections, Einstein rings, and concentrations for the sample of 12 MACS clusters at $z>0.5$ presented in Ebeling et al. (2007) and discussed in Zitrin et al. (2010). We find that simulated clusters produce $\sim 50%$ less arcs than observed clusters do. The medians of the distributions of the Einstein ring sizes differ by $\sim 25%$ between simulations and observations. We estimate that, due to cluster triaxiality and orientation biases affecting the lenses with the largest cross sections, the concentrations of the individual MACS clusters inferred from the lensing analysis should be up to a factor of $\sim 2$ larger than expected from the $Λ$CDM model. The arc statistics, the Einstein ring, and the concentration problems in strong lensing clusters are mitigated but not solved on the basis of our analysis. Nevertheless, due to the lack of redshifts for most of the multiple image systems used for modeling the MACS clusters, the results of this work will need to be verified with additional data. The upcoming CLASH program will provide an ideal sample for extending our comparison (abridged).

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arXiv2011

Imprints of primordial non-Gaussianity on the number counts of cosmic shear peaks

We studied the effect of primordial non-Gaussianity with varied bispectrum shapes on the number counts of signal-to-noise peaks in wide field cosmic shear maps. The two cosmological contributions to this particular weak lensing statistic, namely the chance projection of Large Scale Structure and the occurrence of real, cluster-sized dark matter halos, have been modeled semi-analytically, thus allowing to easily introduce the effect of non-Gaussian initial conditions. We performed a Fisher matrix analysis by taking into account the full covariance of the peak counts in order to forecast the joint constraints on the level of primordial non-Gaussianity and the amplitude of the matter power spectrum that are expected by future wide field imaging surveys. We find that positive-skewed non-Gaussianity increases the number counts of cosmic shear peaks, more so at high signal-to-noise values, where the signal is mostly dominated by massive clusters as expected. The increment is at the level of ~1 for f_NL=10 and ~10 for f_NL=100 for a local shape of the primordial bispectrum, while different bispectrum shapes give generically a smaller effect. For a future survey on the model of the proposed ESA space mission Euclid and by avoiding the strong assumption of being capable to distinguish the weak lensing signal of galaxy clusters from chance projection of Large Scale Structures we forecasted a 1-sigma error on the level of non-Gaussianity of ~30-40 for the local and equilateral models, and of ~100-200 for the less explored enfolded and orthogonal bispectrum shapes.

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arXiv2010

Primordial density perturbations with running spectral index: impact on non-linear cosmic structures

(abridged) We explore the statistical properties of non-linear cosmic structures in a flat $Λ$CDM cosmology in which the index of the primordial power spectrum for scalar perturbations is allowed to depend on the scale. Within the inflationary paradigm, the running of the scalar spectral index can be related to the properties of the inflaton potential, and it is hence of critical importance to test it with all kinds of observations, which cover the linear and non-linear regime of gravitational instability. We focus on the amount of running $α_{\mathrm{S},0}$ allowed by an updated combination of CMB anisotropy data and the 2dF Galaxy Redshift Survey. Our analysis constrains $α_{\mathrm{S},0} = -0.051^{+0.047}_{-0.053}$ $(-0.034^{+0.039}_{-0.040})$ at 95% Confidence Level when (not) taking into account primordial gravitational waves in a ratio as predicted by canonical single field inflation, in agreement with other works. For the cosmological models best fitting the data both with and without running we studied the abundance of galaxy clusters and of rare objects, the halo bias, the concentration of dark matter halos, the Baryon Acoustic Oscillation, the power spectrum of cosmic shear, and the Integrated Sachs-Wolfe effect. We find that counting galaxy clusters in future X-ray and Sunyaev-Zel'dovich surveys could discriminate between the two models, more so if broad redshift information about the cluster samples will be available. Likewise, measurements of the power spectrum of cosmological weak lensing as performed by planned all-sky optical surveys such as EUCLID could detect a running of the primordial spectral index, provided the uncertainties about the source redshift distribution and the underlying matter power spectrum are well under control.

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arXiv2010

The potential of X-ray cluster surveys to constrain primordial non-Gaussianity

We present forecasts for constraints on deviations from Gaussian distribution of primordial density perturbations from future X-ray surveys of galaxy clusters. Our analysis is based on computing the Fisher-Matrix for number counts and large-scale power spectrum of clusters. We consider a survey with high-sensitivity and wide-area to detect about 2.5 x 10^5 extended sources. Based on the self-calibration approach, and including Planck priors in our analysis, we constrain 9 cosmological parameters and 4 nuisance parameters, which define the relation between cluster mass and X-ray flux. Because of the scale dependence of large-scale bias induced by local-shape non-Gaussianity, we find that the power spectrum provides strong constraints on the non-Gaussianity f_nl parameter, which complement the stringent constraints on the power spectrum normalization, σ_8, from the number counts. To quantify the joint constraints on theese two parameters, that specify the timing of structure formation for a fixed background expansion, we define the figure-of-merit FoM_SFT = (det[Cov(sigma_8,f_nl)])^{-1/2}. We find that our surveys constrain deviations from Gaussianity with a precision of Δf_nl~10 at 1 σconfidence level, with FoM_SFT~39. We point out that constraints on f_nl are weakly sensitive to the uncertainties in the knowledge of nuisance parameters. As an application of non-Gaussian constraints from available data, we analyse the impact of positive skewness on the occurrence of XMMU-J2235, a massive distant cluster discovered at z~1.4. We confirm that in a WMAP-7 Gaussian Lambda CDM cosmology, within the survey volume, ~5x10^{-3} objects like this are expected to be found: to increase this probability by a factor of at least 10, one needs to evade either the available constraints on f_nl or sigma_8.

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arXiv2010

Statistical properties of SZ and X-ray cluster detections

Aims. We calibrate the number density, completeness, reliability and the lower mass limit of galaxy-cluster detections through their thermal SZ signal, and compare them to X-ray cluster detections. Methods. We simulate maps of the thermal SZ effect and the X-ray emission from light cones constructed in a large, hydrodynamical, cosmological simulation volume, including realistic noise contributions. The maps are convolved with linear, optimised, single- and multi-band filters to identify local peaks and their signal-to-noise ratios. The resulting peak catalogues are then compared to the halo population in the simulation volume to identify true and spurious detections. Results. Multi-band filtering improves the statistics of SZ cluster detections considerably compared to single-band filtering. Observations with the characteristics of ACT detect clusters with masses M>6-9e13 M_o/h, quite independent of redshift, reach 50% completeness at ~1e14 M_o/h and 100% completeness at ~2e14 M_o/h. Samples are contaminated by only a few per cent spurious detections. This is broadly comparable to X-ray cluster detections with XMM-Newton with 100 ks exposure time in the soft band, except that the mass limit for X-ray detections increases much more steeply with redshift than for SZ detections. A comparison of true and filtered signals in the SZ and X-ray maps confirms that the filters introduce at most a negligible bias.

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arXiv2010

Cosmic shear statistics in cosmologies with non-Gaussian initial conditions

We computed the power spectrum of weak cosmic shear in models with non-Gaussian primordial density fluctuations. Cosmological initial conditions deviating from Gaussianity have recently attracted much attention in the literature, especially with respect to their effect on the formation of non-linear structures and because of the bounds that they can put on the inflationary epoch. The fully non-linear matter power spectrum was evaluated with the use of the physically motivated, semi-analytic halo model, where the mass function and linear halo bias were suitably corrected for non-Gaussian cosmologies. In agreement with previous work, we found that a level of non-Gaussianity compatible with CMB bounds and with positive skewness produces an increase in power of the order of a few percent at intermediate scales. We then used the matter power spectrum, together with observationally motivated background source redshift distributions in order to compute the cosmological weak lensing power spectrum. We found that the degree of deviation from the power spectrum of the reference Gaussian model is small compared to the statistical error expected from even future weak lensing surveys. However, summing the signal over a large range of multipoles can beat down the noise, bringing to a significant detection of non-Gaussianity at the level of $|f_\mathrm{NL}| \simeq $ few tens, when all other cosmological parameters are held fixed. Finally, we have shown that the constraints on the level of non-Gaussianity can be improved by $\sim 20%$ with the use of weak lensing tomography.

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