arXiv subjects

Olivier Doré

Publications and source records attributed to Olivier Doré.

At least 109 records · Page 6Linked to original sources

arXiv2014

Testing Inflation with Large Scale Structure: Connecting Hopes with Reality

The statistics of primordial curvature fluctuations are our window into the period of inflation, where these fluctuations were generated. To date, the cosmic microwave background has been the dominant source of information about these perturbations. Large scale structure is however from where drastic improvements should originate. In this paper, we explain the theoretical motivations for pursuing such measurements and the challenges that lie ahead. In particular, we discuss and identify theoretical targets regarding the measurement of primordial non-Gaussianity. We argue that when quantified in terms of the local (equilateral) template amplitude $f_{\rm NL}^{\rm loc}$ ($f_{\rm NL}^{\rm eq}$), natural target levels of sensitivity are $Δf_{\rm NL}^{\rm loc, eq.} \simeq 1$. We highlight that such levels are within reach of future surveys by measuring 2-, 3- and 4-point statistics of the galaxy spatial distribution. This paper summarizes a workshop held at CITA (University of Toronto) on October 23-24, 2014.

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arXiv2014

Designing an Inflation Galaxy Survey: how to measure $σ(f_{\rm NL}) \sim 1$ using scale-dependent galaxy bias

The most promising method for measuring primordial non-Gaussianity in the post-Planck era is to detect large-scale, scale-dependent galaxy bias. Considering the information in the galaxy power spectrum, we here derive the properties of a galaxy clustering survey that would optimize constraints on primordial non-Gaussianity using this technique. Specifically, we ask the question what survey design is needed to reach a precision $σ(f_{\rm NL}^{\rm loc}) \approx 1$. To answer this question, we calculate the sensitivity to $f_{\rm NL}^{\rm loc}$ as a function of galaxy number density, redshift accuracy and sky coverage. We include the multitracer technique, which helps minimize cosmic variance noise, by considering the possibility of dividing the galaxy sample into stellar mass bins. We show that the ideal survey for $f_{\rm NL}^{\rm loc}$ looks very different than most galaxy redshift surveys scheduled for the near future. Since those are more or less optimized for measuring the BAO scale, they typically require spectroscopic redshifts. On the contrary, to optimize the $f_{\rm NL}^{\rm loc}$ measurement, a deep, wide, multi-band imaging survey is preferred. An uncertainty $σ(f_{\rm NL}^{\rm loc}) = 1$ can be reached with a full-sky survey that is complete to an $i$-band AB magnitude $i \approx 23$ and has a number density $\sim 8$ arcmin$^{-2}$. Requirements on the multi-band photometry are set by a modest photo-$z$ accuracy $σ(z)/(1+z) < 0.1$ and the ability to measure stellar mass with a precision $\sim 0.2$ dex or better (or another proxy for halo mass with equivalent scatter). While here we focus on the information in the power spectrum, even stronger constraints can potentially be obtained with the galaxy bispectrum.

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arXiv2014

Cross-correlation of cosmic far-infrared background anisotropies with large scale structures

We measure the cross-power spectra between luminous red galaxies (LRGs) from the Sloan Digital Sky Survey (SDSS)-III Data Release Eight (DR8) and cosmic infrared background (CIB) anisotropies from Planck and data from the Improved Reprocessing (IRIS) of the Infrared Astronomical Satellite (IRAS) at 353, 545, 857, and 3000 GHz, corresponding to 850, 550, 350 and 100 micron, respectively, in the multipole range 100<l<1000. Using approximately 6.5 10^5 photometrically determined LRGs in 7760 deg^2 of the northern hemisphere in the redshift range 0.45 < z < 0.65, we model the far-infrared background (FIRB) anisotropies with an extended version of the halo model. With these methods, we confirm the basic picture obtained from recent analyses of FIRB anisotropies with Herschel and Planck, that the most efficient halo mass at hosting star forming galaxies is log(M_ eff/M_\odot)=12.84+/-0.15. We estimate the percentage of FIRB anisotropies correlated with LRGs as approximately 11.8 %, 3.9 %, 1.8 %, and 1.0 % of the total at 3000, 857, 545, and 353 GHz, respectively. At redshift z~0.55, the bias of FIRB galaxies with respect to the dark matter density field has the value b_{FIRB}~1.45, and the mean dust temperature of FIRB galaxies is T_d=26 K. Finally, we discuss the impact of present and upcoming cross-correlations with far-infrared background anisotropies on the determination of the global star formation history and the link between galaxies and dark matter.

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arXiv2013

The Synergy between Weak Lensing and Galaxy Redshift Surveys

We study the complementarity of weak lensing (WL) and spectroscopic galaxy clustering (GC) surveys, by forecasting dark energy and modified gravity constraints for three upcoming survey combinations: SuMIRe (Subaru Measurement of Images and Redshifts, the combination of the Hyper Suprime-Cam lensing survey and the Prime Focus Spectrograph redshift survey), EUCLID and WFIRST. From the WL surveys, we take into account both the shear and clustering of the source galaxies and from the GC surveys, we use the three-dimensional clustering of spectroscopic galaxies, including redshift space distortions. A CMB prior is included in all cases. Focusing on the large-scale, two-point function information, we find strong synergy between the two probes. The dark energy figure of merit from WL+GC is up to a factor ~2.5 larger than from either probe alone. Considering modified gravity, if the growth factor f(z) is treated as a free function, it is very poorly constrained by WL or GC alone, but can be measured at the few percent level by the combination of the two. On the other hand, for cosmological constraints derived from (angular) power spectra and considering statistical errors only, it hardly matters whether the surveys overlap on the sky or not. For instance, the dark energy figure of merit for overlapping surveys is at most ~20 % better than in the disjoint case. This modest gain can be traced to the fundamental fact that only a small fraction of the total number of modes sampled by the GC survey (or by the WL survey) contributes to the cross-correlations between WL and GC.

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arXiv2013

Extragalactic Science, Cosmology and Galactic Archaeology with the Subaru Prime Focus Spectrograph (PFS)

The Subaru Prime Focus Spectrograph (PFS) is a massively-multiplexed fiber-fed optical and near-infrared 3-arm spectrograph (N_fiber=2400, 380<lambda<1260nm, 1.3 degree diameter FoV), offering unique opportunities in survey astronomy. Here we summarize the science case feasible for a survey of Subaru 300 nights. We describe plans to constrain the nature of dark energy via a survey of emission line galaxies spanning a comoving volume of 9.3 (Gpc/h)^3 in the redshift range 0.8<z<2.4. In each of 6 redshift bins, the cosmological distances will be measured to 3% precision via BAO, and redshift-space distortions will be used to constrain structure growth to 6% precision. In the GA program, radial velocities and chemical abundances of stars in the Milky Way and M31 will be used to infer the past assembly histories of spiral galaxies and the structure of their dark matter halos. Data will be secured for 10^6 stars in the Galactic thick-disk, halo and tidal streams as faint as V~22, including stars with V < 20 to complement the goals of the Gaia mission. A medium-resolution mode with R = 5000 to be implemented in the red arm will allow the measurement of multiple alpha-element abundances and more precise velocities for Galactic stars, elucidating the detailed chemo-dynamical structure and evolution of each of the main stellar components of the Milky Way Galaxy and of its dwarf spheroidal galaxies. For the extragalactic program, our simulations suggest the wide avelength range will be powerful in probing the galaxy population and its clustering over a wide redshift range. We propose to conduct a color-selected survey of 1<z<2 galaxies and AGN over 16 deg^2 to J~23.4, yielding a fair sample of galaxies with stellar masses above ~10^{10}Ms at z~2. A two-tiered survey of higher redshift LBGs and LAEs will quantify the properties of early systems close to the reionization epoch.

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arXiv2013

Using Cross-Correlations to Calibrate Lensing Source Redshift Distributions: Improving Cosmological Constraints from Upcoming Weak Lensing Surveys

Cross-correlations between the galaxy number density in a lensing source sample and that in an overlapping spectroscopic sample can in principle be used to calibrate the lensing source redshift distribution. In this paper, we study in detail to what extent this cross-correlation method can mitigate loss of cosmological information in upcoming weak lensing surveys (combined with a CMB prior) due to lack of knowledge of the source distribution. We consider a scenario where photometric redshifts are available, and find that, unless the photometric redshift distribution p(z_{ph}|z) is calibrated very accurately a priori (bias and scatter known to ~0.002 for, e.g., EUCLID), the additional constraint on p(z_{ph}|z) from the cross correlation technique to a large extent restores the cosmological information originally lost due to the uncertainty in dn/dz(z). Considering only the gain in photo-z accuracy and not the additional cosmological information, enhancements of the dark energy figure of merit of up to a factor of 4 (40) can be achieved for a SuMIRe (Subaru Measurement of Images and Redshifts, the combination of the Hyper Suprime Cam lensing survey and the Prime Focus Spectrograph redshift survey)-like (EUCLID-like) combination of lensing and redshift surveys. However, the success of the method is strongly sensitive to our knowledge of the galaxy bias evolution in the source sample. If this bias is modeled by a free parameter in each of a large number of redshift bins, we find that a prior of order 0.01 is needed on b_i \sqrt{Δz} in each redshift slice (where Δz is the bin width and b_i the value of the galaxy bias in the i-th source bin) to optimize the gains from the cross-correlation method (i.e. to approach the cosmology constraints attainable if the bias were known exactly).[abridged]

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arXiv2013

The redshift-evolution of the distribution of star formation among dark matter halos as seen in the infrared

[Abridged] Recent studies revealed a strong correlation between the star formation rate (SFR) and stellar mass of star-forming galaxies, the so-called star-forming main sequence. An empirical modeling approach (2-SFM) which distinguishes between the main sequence and rarer starburst galaxies is capable of reproducing most statistical properties of infrared galaxies. In this paper, we extend this approach by establishing a connection between stellar mass and halo mass with the technique of abundance matching. Based on a few, simple assumptions and a physically motivated formalism, our model successfully predicts the (cross-)power spectra of the cosmic infrared background (CIB), the cross-correlation between CIB and cosmic microwave background (CMB) lensing, and the correlation functions of bright, resolved infrared galaxies measured by Herschel, Planck, ACT and SPT. We use this model to infer the redshift distribution these observables, as well as the level of correlation between CIB-anisotropies at different wavelengths. We also predict that more than 90% of cosmic star formation activity occurs in halos with masses between 10^11.5 and 10^13.5 Msun. Taking into account subsequent mass growth of halos, this implies that the majority of stars were initially (at z>3) formed in the progenitors of clusters, then in groups at 0.5<z<3 and finally in Milky-Way-like halos at z<0.5. At all redshifts, the dominant contribution to the star formation rate density stems from halos of mass ~10^12 Msun, in which the instantaneous star formation efficiency is maximal (~70%). The strong redshift-evolution of SFR in the galaxies that dominate the CIB is thus plausibly driven by increased accretion from the cosmic web onto halos of this characteristic mass scale. Material available at http://irfu.cea.fr/Sap/Phocea/Page/index.php?id=537.

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arXiv2013

Baryons do trace dark matter 380,000 years after the big bang: Search for compensated isocurvature perturbations with WMAP 9-year data

Primordial isocurvature fluctuations between photons and either neutrinos or non-relativistic species such as baryons or dark matter are known to be sub-dominant to adiabatic fluctuations. Perturbations in the relative densities of baryons and dark matter (known as compensated isocurvature perturbations, or CIPs), however, are surprisingly poorly constrained. CIPs leave no imprint in the cosmic microwave background (CMB) on observable scales, at least at linear order in their amplitude and zeroth order in the amplitude of adiabatic perturbations. It is thus not yet empirically known if baryons trace dark matter at the surface of last scattering. If CIPs exist, they would spatially modulate the Silk damping scale and acoustic horizon, causing distinct fluctuations in the CMB temperature/polarization power spectra across the sky: this effect is first order in both the CIP and adiabatic mode amplitudes. Here, temperature data from the Wilkinson Microwave Anisotropy Probe (WMAP) are used to conduct the first CMB-based observational search for CIPs, using off-diagonal correlations and the CMB trispectrum. Reconstruction noise from weak lensing and point sources is shown to be negligible for this data set. No evidence for CIPs is observed, and a 95%-confidence upper limit of $1.1\times 10^{-2}$ is imposed to the amplitude of a scale-invariant CIP power spectrum. This limit agrees with CIP sensitivity forecasts for WMAP, and is competitive with smaller scale constraints from measurements of the baryon fraction in galaxy clusters. It is shown that the root-mean-squared CIP amplitude on 5-100 degree scales is smaller than 0.07-0.17 (depending on the scale) at the 95%-confidence level. Temperature data from the Planck satellite will provide an even more sensitive probe for the existence of CIPs, as will the upcoming ACTPol and SPTPol experiments on smaller angular scales.

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arXiv2012

The Weight of Emptiness: The Gravitational Lensing Signal of Stacked Voids

The upcoming new generation of spectroscopic galaxy redshift surveys will provide large samples of cosmic voids, the distinct, large underdense structures in the universe. Combining these with future galaxy imaging surveys, we study the prospects of probing the underlying matter distribution in and around cosmic voids via the weak gravitational lensing effects of stacked voids, utilizing both shear and magnification information. The statistical precision is greatly improved by stacking together a large number of voids along different lines of sight, even when taking into account the impact of inherent miscentering and projection effects. We show that Dark Energy Task Force Stage IV surveys, such as the Euclid satellite and the Large Synoptic Survey Telescope, should be able to detect the void lensing signal with sufficient precision from stacking abundant medium-sized voids, thus providing direct constraints on the matter density profile of voids independent of assumptions on galaxy bias.

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arXiv2012

Testing Gravity Using Large-Scale Redshift-Space Distortions

We use Luminous Red Galaxies from the Sloan Digital Sky Survey II to test the cosmological structure growth in two alternatives to the standard LCDM+GR cosmological model. We compare observed three-dimensional clustering in SDSS DR7 with theoretical predictions for the standard vanilla LCDM+GR model, Unified Dark Matter cosmologies and the normal branch DGP. In computing the expected correlations in UDM cosmologies, we derive a parameterized formula for the growth factor in these models. For our analysis we apply the methodology tested in Raccanelli et al. 2010 and use the measurements of Samushia et al. 2011, that account for survey geometry, non-linear and wide-angle effects and the distribution of pair orientation. We show that the estimate of the growth rate is potentially degenerate with wide-angle effects, meaning that extremely accurate measurements of the growth rate on large scales will need to take such effects into account. We use measurements of the zeroth and second order moments of the correlation function from SDSS DR7 data and the Large Suite of Dark Matter Simulations, and perform a likelihood analysis to constrain the parameters of the models. Using information on the clustering up to r_max = 120 Mpc/h, and after marginalizing over the bias, we find, for UDM models, a speed of sound < 6.1e-4, and, for the nDGP model, a cross-over scale r_c > 340 Mpc, at 95% confidence level.

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arXiv2012

Where stars form and live at high redshift: clues from the infrared

The relation between dark matter halos and the loci of star formation at high redshift is a pressing question in contemporary cosmology. Matching the abundance of halos to the abundance of infrared (IR) galaxies, we explicit the link between dark matter halo mass (Mh), stellar mass (M*) and star-formation rate (SFR) up to a redshift of 2. Our findings are five-fold. First, we find a strong evolution of the relation between M* and SFR as a function of redshift with an increase of sSFR = SFR/M* by a factor ~30 between z=0 and z= 2.3. Second, we observe a decrease of sSFR with stellar mass. These results reproduce observed trends at redshift z>0.3. Third, we find that the star formation is most efficient in dark matter halos with Mh~5x10^11 Msun, with hints of an increase of this mass with redshift. Fourth, we find that SFR/Mh increases by a factor ~15 between z = 0 and z = 2.3. Finally we find that the SFR density is dominated by halo masses close to ~7x10^11 Msun at all redshift, with a rapid decrease at lower and higher halo masses. Despite its simplicity, our novel use of IR observations unveils some characteristic mass-scales governing star formation at high redshift.

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arXiv2012

Compensated Isocurvature Perturbations and the Cosmic Microwave Background

Measurements of cosmic microwave background (CMB) anisotropies constrain isocurvature fluctuations between photons and non-relativistic particles to be sub-dominant to adiabatic fluctuations. Perturbations in the relative number densities of baryons and dark matter, however, are surprisingly poorly constrained. In fact, baryon-density perturbations of fairly large amplitude may exist if they are compensated by dark-matter perturbations, so that the total density remains unchanged. These compensated isocurvature perturbations (CIPs) leave no imprint on the CMB at observable scales, at linear order in their amplitude. B modes in the CMB polarization are generated at reionization through the modulation of the optical depth by CIPs, but this induced polarization is small. The strongest known constraint $\lesssim 10%$ to the CIP amplitude comes from galaxy cluster baryon fractions. Here it is shown that modulation of the baryon density by the CIP at and before the decoupling of Thomson scattering at $z\sim 1100$ gives rise to CMB effects several orders of magnitude larger than those considered before. Polarization B modes are induced, as are correlations between temperature/polarization spherical-harmonic coefficients of different $lm$. It is shown that the CIP field at the surface of last scatter can be measured with these higher-order correlations. The sensitivity of ongoing and future experiments to these fluctuations is estimated. Data from the WMAP, ACT, SPT, and Spider experiments will be sensitive to fluctuations with amplitude $\sim 5-10%$. The Planck satellite and Polarbear experiment will be sensitive to fluctuations with amplitude $\sim 3%$. SPTPol, ACTPol, and future space-based polarization methods will probe amplitudes as low as $\sim 0.4%-0.6%$. In the cosmic variance limit, the lowest amplitude CIPs that could be detected with the CMB are of amplitude $\sim 0.05%$.

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arXiv2012

Do baryons trace dark matter in the early universe?

Baryon-density perturbations of large amplitude may exist if they are compensated by dark-matter perturbations so that the total density remains unchanged. Big-bang nucleosynthesis and galaxy clusters allow the amplitudes of these compensated isocurvature perturbations (CIPs) to be as large as $\sim10%$. CIPs will modulate the power spectrum of cosmic microwave background (CMB) fluctuations---those due to the usual adiabatic perturbations---as a function of position on the sky. This leads to correlations between different spherical-harmonic coefficients of the temperature/polarization map, and it induces B modes in the CMB polarization. Here, the magnitude of these effects is calculated and techniques to measure them are introduced. While a CIP of this amplitude can be probed on the largest scales with WMAP, forthcoming CMB experiments should improve the sensitivity to CIPs by at least an order of magnitude.

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arXiv2011

Modeling the evolution of infrared galaxies : clustering of galaxies in the Cosmic Infrared Background

Star-forming galaxies are a highly biased tracer of the underlying dark matter density field. Their clustering can be studied through the cosmic infrared background anisotropies. These anisotropies have been measured from 100 \mum to 2 mm in the last few years. In this paper, we present a fully parametric model allowing a joint analysis of these recent observations. In order to develop a coherent model at various wavelengths, we rely on two building blocks. The first one is a parametric model that describes the redshift evolution of the luminosity function of star-forming galaxies. It compares favorably to measured differential number counts and luminosity functions. The second one is a halo model based description of the clustering of galaxies. Starting from a fiducial model, we investigate parameter degeneracies using a Fisher analysis. We then discuss how halo of different mass and redshift, how LIRGs and ULIRGs, contribute to the CIB angular power spectra. From the Fisher analysis, we conclude that we cannot constrain the parameters of the model of evolution of galaxies using clustering data only. The use of combined data of C\ell, counts and luminosity functions improves slightly the constraints but does not remove any degeneracies. On the contrary, the measurement of the anisotropies allows us to set interesting constraints on the halo model parameters, even if some strong degeneracies remain. Using our fiducial model, we establish that the 1-halo and 2-halo terms are not sensitive to the same mass regime. We also illustrate how the 1-halo term can be misinterpreted with the Poisson noise term. Conclusions. We present a new model of the clustering of infrared galaxies. However such a model has a few limitations, as the parameters of the halo occupation suffer from strong degeneracies.

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arXiv2011

Primordial Gravitational Wave Detectability with Deep Small-Sky CMB Experiments

We use Bayesian estimation on direct T-Q-U CMB polarization maps to forecast errors on the tensor-to- scalar power ratio r, and hence on primordial gravitational waves, as a function of sky coverage fsky. This method filters the quadratic pixel-pixel space into the optimal combinations needed for r detection for cut skies, providing enhanced information over a first-step linear separation into a combination of E, B and mixed modes, and ignoring the latter. With current computational power and for typical resolutions appropriate for r detection, the large matrix inversions required are accurate and fast. We explore two classes of experiments. One is motivated by a long duration balloon experiment like Spider, with pixel noise \propto \sqrt{fsky} for a specified observing period, but also applies to ground-based array experiments. We find that, ignoring systematic effects and foregrounds, an experiment with Spider-like noise over fsky ~0.02-0.2 could place a 2sigma_r ~0.014 (~95% CL) bound, rising to 0.02 with an L-dependent foreground residual. We contrast this with a Planck-like fixed instrumental noise as fsky varies, which gives a Galaxy-masked (fsky = 0.75) 2sigma_r ~0.015, rising to ~0.05 with the foreground residuals. Using for a figure of merit the (marginalized) 1D Shannon entropy of r, taken relative to the first 2003 WMAP1 CMB-only constraint, gives -1.7 (-1.9) bits from the 2010 WMAP7+ACT (2011 WMAP7+SPT) data, forecasts of -6 bits from Spider (plus Planck), of up to -11 bits for post-Planck satellites and -13 bits for a perfect cosmic variance limited experiment. We thus confirm the wisdom of the current strategy for r detection of deeply probed patches covering the fsky minimum-error trough with balloon and ground experiments.

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arXiv2011

Intensity Mapping with Carbon Monoxide Emission Lines and the Redshifted 21 cm Line

We quantify the prospects for using emission lines from rotational transitions of the CO molecule to perform an `intensity mapping' observation at high redshift during the Epoch of Reionization (EoR). The aim of CO intensity mapping is to observe the combined CO emission from many unresolved galaxies, to measure the spatial fluctuations in this emission, and use this as a tracer of large scale structure at very early times in the history of our Universe. This measurement would help determine the properties of molecular clouds -- the sites of star formation -- in the very galaxies that reionize the Universe. We further consider the possibility of cross-correlating CO intensity maps with future observations of the redshifted 21 cm line. The cross spectrum is less sensitive to foreground contamination than the auto power spectra, and can therefore help confirm the high redshift origin of each signal. Furthermore, the cross spectrum measurement would help extract key information about the EoR, especially regarding the size distribution of ionized regions. We discuss uncertainties in predicting the CO signal at high redshift, and discuss strategies for improving these predictions. Under favorable assumptions, and feasible specifications for a CO survey mapping the CO(2-1) and CO(1-0) lines, the power spectrum of CO emission fluctuations and its cross spectrum with future 21 cm measurements from the MWA are detectable at high significance.

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arXiv2011

Modeling Extragalactic Foregrounds and Secondaries for Unbiased Estimation of Cosmological Parameters From Primary CMB Anisotropy

Using the latest physical modeling and constrained by the most recent data, we develop a phenomenological parameterized model of the contributions to intensity and polarization maps at millimeter wavelengths from external galaxies and Sunyaev-Zeldovich effects. We find such modeling to be necessary for estimation of cosmological parameters from Planck data. For example, ignoring the clustering of the infrared background would result in a bias in n_s of 7 sigma. We show that the simultaneous marginalization over a full foreground model can eliminate such biases, while increasing the statistical uncertainty in cosmological parameters by less than 20%. The small increases in uncertainty can be significantly reduced with the inclusion of higher-resolution ground-based data. The multi-frequency analysis we employ involves modeling 46 total power spectra and marginalization over 17 foreground parameters. We show that we can also reduce the data to a best estimate of the CMB power spectra, and just two principal components (with constrained amplitudes) describing residual foreground contamination.

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arXiv2009

A step towards testing general relativity using weak gravitational lensing and redshift surveys

Using the linear theory of perturbations in General Relativity, we express a set of consistency relations that can be observationally tested with current and future large scale structure surveys. We then outline a stringent model-independent program to test gravity on cosmological scales. We illustrate the feasibility of such a program by jointly using several observables like peculiar velocities, galaxy clustering and weak gravitational lensing. After addressing possible observational or astrophysical caveats like galaxy bias and redshift uncertainties, we forecast in particular how well one can predict the lensing signal from a cosmic shear survey using an over-lapping galaxy survey. We finally discuss the specific physics probed this way and illustrate how $f(R)$ gravity models would fail such a test.

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