In this "Invisible Universe" proceedings, we introduce the Dark Energy Universe Simulation Series... more In this "Invisible Universe" proceedings, we introduce the Dark Energy Universe Simulation Series (DEUSS) which aim at investigating the imprints of realistic dark energy models on cosmic structure formation. It represents the largest dynamical dark energy simulation suite to date in term of spatial dynamics. We first present the 3 realistic dark energy models (calibrated on latest SNIa and CMB data): ΛCDM, quintessence with Ratra-Peebles potential, and quintessence with Sugra potential. We then isolate various contributions for non-linear matter power spectra from a series of pre-DEUSS highresolution simulations (130 million particles). Finally, we introduce DEUSS which consist in 9 Grand Challenge runs with 1 billion particles each thus probing scales from 4 Gpc down to 3 kpc at z=0. Our goal is to make these simulations available to the community through the "Dark Energy Universe Virtual Observatory" (DEUVO), and the "Dark Energy Universe Simulations" (DEUS) consortium.
The effect of spatial variations of the Newton constant on the cosmic microwave background is stu... more The effect of spatial variations of the Newton constant on the cosmic microwave background is studied. Constraints on the strong equivalence principle violation at the recombination time are then obtained with the help of WMAP data and of the standard theory of big-bang nucleosynthesis.
The latest results in cosmography as well as the lat-est observations of the cosmic microwave bac... more The latest results in cosmography as well as the lat-est observations of the cosmic microwave background (CMB) and of supernovae have reinforced the emer-gence of a canonical paradigm for cosmology. Most of the cosmological parameters constituting this con-cordance ...
Publications of the Astronomical Society of the Pacific, 2018
We report on the search for optical counterparts of Planck Sunyaev-Zel'dovich (SZ) cluster candid... more We report on the search for optical counterparts of Planck Sunyaev-Zel'dovich (SZ) cluster candidates using a 0.6 m non-professional telescope. Among the observed sources, an unconfirmed candidate, PSZ2 G156.24+22.32, is found to be associated with a region of more than 100 galaxies within a 3 arcminute radius around the Sunyaev-Zel'dovich maximum signal coordinates. Using 14 hours of cumulated exposure over the Sloan color filters g', r', i', and z', we estimate the photometric redshift of these galaxies at z phot = 0.29 ± 0.08. Using the red-sequence galaxy method gives a photometric redshift of . Combined with the Planck SZ proxy mass function, this would favor a cluster of 4.4 × 1014 solar masses. This result suggests that a dedicated pool of observatories equipped with such instruments could collectively contribute to optical follow-up programs of massive cluster candidates at moderate redshifts.
According to the general theory of relativity, the current paradigm for gravitation and concordan... more According to the general theory of relativity, the current paradigm for gravitation and concordant observational data, about 95% of the Universe’s content is only perceivable through gravitational effects. Consolidating the predictions of this theory is then of primordial importance. Those predictions are structured around two dimensional constants : Newton’s and Einstein’s constants. The former, namely the universal constant, yields the universality of free fall of light and compact objects. The latter, also named cosmological constant, explains the late expansion acceleration of the Universe on cosmological scales. The main goal of this thesis is to explore the foundations of general relativity by promoting these constants as dynamical fields.
First of all, we propose a generic test seeking for possible Newton’s constant variations in the primeval plasma. The modified weight of baryons translates the equilibrium point of the acoustic oscillations. A constraint on the amplitude of such variations is extracted from the anisotropies of the cosmic microwave background. Secondly, we scrutinize a simple modification of general relativity providing a minimal violation of the strong equivalence principle. Although the additional scalar field acts as a dark radiation at the cosmological expansion level, the imprint left on the matter field perturbations is clearly distinguishable from other radiations because of the particular scalar field anisotropic stress. Several constraints for this alternative gravitational theory are derived from the analysis of the cosmic microwave background, Type Ia supernovae and the measure of the Lemaître-Hubble constant.
Finally, we replace the cosmological constant by a quintessence field. For selected realistic models agreeing with current cosmological data, it is shown that the non-linear processes driving the growth of matter’s large scale structures encode the nature and the dynamics of dark energy.
Although the confrontation between the investigated alternative models and available cosmological data currently does not raise deviation to the concordant ΛCDM model, the present study shows that predictions and signatures of these models are unique compared to the standard scenario.
The universality of the halo mass function is investigated in the context of dark energy cosmolog... more The universality of the halo mass function is investigated in the context of dark energy cosmologies. This widely used approximation assumes that the mass function can be expressed as a function of the matter density Ω m and the root-mean-square linear density fluctuation σ only, with no explicit dependence on the properties of dark energy or redshift. In order to test this hypothesis we run a series of 15 high-resolution N-body simulations for different cosmological models. These consists of three ΛCDM cosmologies best fitting WMAP-1, 3 and 5 years data, which are used for model comparison, and three toy-models characterized by a Ratra-Peebles quintessence potential with different slopes and amounts of dark energy density. These toy models have very different evolutionary histories at the background and linear level, but share the same σ 8 value. For each of these models we measure the mass function from catalogues of halos identified in the simulations using the Friend-of-Friend (FoF) algorithm. We find redshift-dependent deviations from a universal behaviour, well above numerical uncertainties and of non-stochastic origin, which are correlated with the linear growth factor of the investigated cosmologies. Using the spherical collapse as guidance, we show that such deviations are caused by the cosmology dependence of the non-linear collapse and virialization process. For practical applications, we provide a fitting formula of the mass function accurate to 5 percents over the all range of investigated cosmologies. We also derive an empirical relation between the FoF linking parameter and the virial overdensity which can account for most of the deviations from an exact universal behavior. Overall these results suggest that measurements of the halo mass function at z = 0 can provide additional constraints on dark energy since it carries a fossil record of the past cosmic evolution.
Quintessence has been proposed to account for dark energy in the Universe. This component causes ... more Quintessence has been proposed to account for dark energy in the Universe. This component causes a typical modification of the background cosmic expansion, which in addition to its clustering properties, can leave a potentially distinctive signature on large scale structures. Many previous studies have investigated this topic, particularly in relation to the non-linear regime of structure formation. However, no careful pre-selection of viable quintessence models with high precision cosmological data was performed. Here we show that this has led to a misinterpretation (and underestimation) of the imprint of quintessence on the distribution of large scale structures. To this purpose we perform a likelihood analysis of the combined Supernova Ia UNION dataset and WMAP5-years data to identify realistic quintessence models. These are specified by different model parameter values, but still statistically indistinguishable from the vanilla ΛCDM. Differences are especially manifest in the predicted amplitude and shape of the linear matter power spectrum, though these remain within the uncertainties of the SDSS data. We use these models as benchmark for studying the clustering properties of dark matter halos by performing a series of high resolution N-body simulations. In this first paper, we specifically focus on the non-linear matter power spectrum. We find that realistic quintessence models allow for relevant differences of the dark matter distribution with the respect to the ΛCDM scenario well into the non-linear regime, with deviations up to 40% in the non-linear power spectrum. Such differences are shown to depend on the nature of DE, as well as the scale and epoch considered. At small scales (k ∼ 1 − 5 h Mpc −1 , depending on the redshift) the structure formation process is about 20% more efficient than in ΛCDM. We show that these imprints are a specific record of the cosmic structure formation history in dark energy cosmologies and therefore cannot be accounted in standard fitting functions of the non-linear matter power spectrum.
In this "Invisible Universe" proceedings, we introduce the Dark Energy Universe Simulation Series... more In this "Invisible Universe" proceedings, we introduce the Dark Energy Universe Simulation Series (DEUSS) which aim at investigating the imprints of realistic dark energy models on cosmic structure formation. It represents the largest dynamical dark energy simulation suite to date in term of spatial dynamics. We first present the 3 realistic dark energy models (calibrated on latest SNIa and CMB data): ΛCDM, quintessence with Ratra-Peebles potential, and quintessence with Sugra potential. We then isolate various contributions for non-linear matter power spectra from a series of pre-DEUSS highresolution simulations (130 million particles). Finally, we introduce DEUSS which consist in 9 Grand Challenge runs with 1 billion particles each thus probing scales from 4 Gpc down to 3 kpc at z=0. Our goal is to make these simulations available to the community through the "Dark Energy Universe Virtual Observatory" (DEUVO), and the "Dark Energy Universe Simulations" (DEUS) consortium.
The effect of spatial variations of the Newton constant on the cosmic microwave background is stu... more The effect of spatial variations of the Newton constant on the cosmic microwave background is studied. Constraints on the strong equivalence principle violation at the recombination time are then obtained with the help of WMAP data and of the standard theory of big-bang nucleosynthesis.
We study the effect of a violation of the strong equivalence principle (SEP) on the cosmic microw... more We study the effect of a violation of the strong equivalence principle (SEP) on the cosmic microwave background (CMB). Such a violation would modify the weight of baryons in the primordial gravitational potentials and hence their impact in the establishment of the photon-baryon plasma acoustic oscillations before recombination. This cosmological Nordtvedt effect alters the odd peaks height of the CMB temperature anisotropy power spectrum. A gravitational baryonic mass density of the universe may already be inferred at the first peak scale from the analysis of WMAP data. Experimental constraints on a primordial SEP violation are derived from a comparison with the universe's inertial baryonic mass density measured either in a full analysis of the CMB, or in the framework of the standard big bang nucleosynthesis (BBN).
A Nordtvedt effect at cosmological scales affects the acoustic oscillations imprinted in the cosm... more A Nordtvedt effect at cosmological scales affects the acoustic oscillations imprinted in the cosmic microwave background. The gravitational baryonic mass density of the universe is inferred at the first peak scale from WMAP data. The independent determination of the inertial baryonic mass density through the measurement of the deuterium abundance in the framework of standard big bang nucleosynthesis leads to a new constraint on a possible violation of the strong equivalence principle at the recombination time. PACS numbers: 98.80.Es, 04.80.Cc, 98.70.Vc, 98.80.Ft
In this "Invisible Universe" proceedings, we introduce the Dark Energy Universe Simulation Series... more In this "Invisible Universe" proceedings, we introduce the Dark Energy Universe Simulation Series (DEUSS) which aim at investigating the imprints of realistic dark energy models on cosmic structure formation. It represents the largest dynamical dark energy simulation suite to date in term of spatial dynamics. We first present the 3 realistic dark energy models (calibrated on latest SNIa and CMB data): ΛCDM, quintessence with Ratra-Peebles potential, and quintessence with Sugra potential. We then isolate various contributions for non-linear matter power spectra from a series of pre-DEUSS highresolution simulations (130 million particles). Finally, we introduce DEUSS which consist in 9 Grand Challenge runs with 1 billion particles each thus probing scales from 4 Gpc down to 3 kpc at z=0. Our goal is to make these simulations available to the community through the "Dark Energy Universe Virtual Observatory" (DEUVO), and the "Dark Energy Universe Simulations" (DEUS) consortium.
The effect of spatial variations of the Newton constant on the cosmic microwave background is stu... more The effect of spatial variations of the Newton constant on the cosmic microwave background is studied. Constraints on the strong equivalence principle violation at the recombination time are then obtained with the help of WMAP data and of the standard theory of big-bang nucleosynthesis.
The latest results in cosmography as well as the lat-est observations of the cosmic microwave bac... more The latest results in cosmography as well as the lat-est observations of the cosmic microwave background (CMB) and of supernovae have reinforced the emer-gence of a canonical paradigm for cosmology. Most of the cosmological parameters constituting this con-cordance ...
Publications of the Astronomical Society of the Pacific, 2018
We report on the search for optical counterparts of Planck Sunyaev-Zel'dovich (SZ) cluster candid... more We report on the search for optical counterparts of Planck Sunyaev-Zel'dovich (SZ) cluster candidates using a 0.6 m non-professional telescope. Among the observed sources, an unconfirmed candidate, PSZ2 G156.24+22.32, is found to be associated with a region of more than 100 galaxies within a 3 arcminute radius around the Sunyaev-Zel'dovich maximum signal coordinates. Using 14 hours of cumulated exposure over the Sloan color filters g', r', i', and z', we estimate the photometric redshift of these galaxies at z phot = 0.29 ± 0.08. Using the red-sequence galaxy method gives a photometric redshift of . Combined with the Planck SZ proxy mass function, this would favor a cluster of 4.4 × 1014 solar masses. This result suggests that a dedicated pool of observatories equipped with such instruments could collectively contribute to optical follow-up programs of massive cluster candidates at moderate redshifts.
According to the general theory of relativity, the current paradigm for gravitation and concordan... more According to the general theory of relativity, the current paradigm for gravitation and concordant observational data, about 95% of the Universe’s content is only perceivable through gravitational effects. Consolidating the predictions of this theory is then of primordial importance. Those predictions are structured around two dimensional constants : Newton’s and Einstein’s constants. The former, namely the universal constant, yields the universality of free fall of light and compact objects. The latter, also named cosmological constant, explains the late expansion acceleration of the Universe on cosmological scales. The main goal of this thesis is to explore the foundations of general relativity by promoting these constants as dynamical fields.
First of all, we propose a generic test seeking for possible Newton’s constant variations in the primeval plasma. The modified weight of baryons translates the equilibrium point of the acoustic oscillations. A constraint on the amplitude of such variations is extracted from the anisotropies of the cosmic microwave background. Secondly, we scrutinize a simple modification of general relativity providing a minimal violation of the strong equivalence principle. Although the additional scalar field acts as a dark radiation at the cosmological expansion level, the imprint left on the matter field perturbations is clearly distinguishable from other radiations because of the particular scalar field anisotropic stress. Several constraints for this alternative gravitational theory are derived from the analysis of the cosmic microwave background, Type Ia supernovae and the measure of the Lemaître-Hubble constant.
Finally, we replace the cosmological constant by a quintessence field. For selected realistic models agreeing with current cosmological data, it is shown that the non-linear processes driving the growth of matter’s large scale structures encode the nature and the dynamics of dark energy.
Although the confrontation between the investigated alternative models and available cosmological data currently does not raise deviation to the concordant ΛCDM model, the present study shows that predictions and signatures of these models are unique compared to the standard scenario.
The universality of the halo mass function is investigated in the context of dark energy cosmolog... more The universality of the halo mass function is investigated in the context of dark energy cosmologies. This widely used approximation assumes that the mass function can be expressed as a function of the matter density Ω m and the root-mean-square linear density fluctuation σ only, with no explicit dependence on the properties of dark energy or redshift. In order to test this hypothesis we run a series of 15 high-resolution N-body simulations for different cosmological models. These consists of three ΛCDM cosmologies best fitting WMAP-1, 3 and 5 years data, which are used for model comparison, and three toy-models characterized by a Ratra-Peebles quintessence potential with different slopes and amounts of dark energy density. These toy models have very different evolutionary histories at the background and linear level, but share the same σ 8 value. For each of these models we measure the mass function from catalogues of halos identified in the simulations using the Friend-of-Friend (FoF) algorithm. We find redshift-dependent deviations from a universal behaviour, well above numerical uncertainties and of non-stochastic origin, which are correlated with the linear growth factor of the investigated cosmologies. Using the spherical collapse as guidance, we show that such deviations are caused by the cosmology dependence of the non-linear collapse and virialization process. For practical applications, we provide a fitting formula of the mass function accurate to 5 percents over the all range of investigated cosmologies. We also derive an empirical relation between the FoF linking parameter and the virial overdensity which can account for most of the deviations from an exact universal behavior. Overall these results suggest that measurements of the halo mass function at z = 0 can provide additional constraints on dark energy since it carries a fossil record of the past cosmic evolution.
Quintessence has been proposed to account for dark energy in the Universe. This component causes ... more Quintessence has been proposed to account for dark energy in the Universe. This component causes a typical modification of the background cosmic expansion, which in addition to its clustering properties, can leave a potentially distinctive signature on large scale structures. Many previous studies have investigated this topic, particularly in relation to the non-linear regime of structure formation. However, no careful pre-selection of viable quintessence models with high precision cosmological data was performed. Here we show that this has led to a misinterpretation (and underestimation) of the imprint of quintessence on the distribution of large scale structures. To this purpose we perform a likelihood analysis of the combined Supernova Ia UNION dataset and WMAP5-years data to identify realistic quintessence models. These are specified by different model parameter values, but still statistically indistinguishable from the vanilla ΛCDM. Differences are especially manifest in the predicted amplitude and shape of the linear matter power spectrum, though these remain within the uncertainties of the SDSS data. We use these models as benchmark for studying the clustering properties of dark matter halos by performing a series of high resolution N-body simulations. In this first paper, we specifically focus on the non-linear matter power spectrum. We find that realistic quintessence models allow for relevant differences of the dark matter distribution with the respect to the ΛCDM scenario well into the non-linear regime, with deviations up to 40% in the non-linear power spectrum. Such differences are shown to depend on the nature of DE, as well as the scale and epoch considered. At small scales (k ∼ 1 − 5 h Mpc −1 , depending on the redshift) the structure formation process is about 20% more efficient than in ΛCDM. We show that these imprints are a specific record of the cosmic structure formation history in dark energy cosmologies and therefore cannot be accounted in standard fitting functions of the non-linear matter power spectrum.
In this "Invisible Universe" proceedings, we introduce the Dark Energy Universe Simulation Series... more In this "Invisible Universe" proceedings, we introduce the Dark Energy Universe Simulation Series (DEUSS) which aim at investigating the imprints of realistic dark energy models on cosmic structure formation. It represents the largest dynamical dark energy simulation suite to date in term of spatial dynamics. We first present the 3 realistic dark energy models (calibrated on latest SNIa and CMB data): ΛCDM, quintessence with Ratra-Peebles potential, and quintessence with Sugra potential. We then isolate various contributions for non-linear matter power spectra from a series of pre-DEUSS highresolution simulations (130 million particles). Finally, we introduce DEUSS which consist in 9 Grand Challenge runs with 1 billion particles each thus probing scales from 4 Gpc down to 3 kpc at z=0. Our goal is to make these simulations available to the community through the "Dark Energy Universe Virtual Observatory" (DEUVO), and the "Dark Energy Universe Simulations" (DEUS) consortium.
The effect of spatial variations of the Newton constant on the cosmic microwave background is stu... more The effect of spatial variations of the Newton constant on the cosmic microwave background is studied. Constraints on the strong equivalence principle violation at the recombination time are then obtained with the help of WMAP data and of the standard theory of big-bang nucleosynthesis.
We study the effect of a violation of the strong equivalence principle (SEP) on the cosmic microw... more We study the effect of a violation of the strong equivalence principle (SEP) on the cosmic microwave background (CMB). Such a violation would modify the weight of baryons in the primordial gravitational potentials and hence their impact in the establishment of the photon-baryon plasma acoustic oscillations before recombination. This cosmological Nordtvedt effect alters the odd peaks height of the CMB temperature anisotropy power spectrum. A gravitational baryonic mass density of the universe may already be inferred at the first peak scale from the analysis of WMAP data. Experimental constraints on a primordial SEP violation are derived from a comparison with the universe's inertial baryonic mass density measured either in a full analysis of the CMB, or in the framework of the standard big bang nucleosynthesis (BBN).
A Nordtvedt effect at cosmological scales affects the acoustic oscillations imprinted in the cosm... more A Nordtvedt effect at cosmological scales affects the acoustic oscillations imprinted in the cosmic microwave background. The gravitational baryonic mass density of the universe is inferred at the first peak scale from WMAP data. The independent determination of the inertial baryonic mass density through the measurement of the deuterium abundance in the framework of standard big bang nucleosynthesis leads to a new constraint on a possible violation of the strong equivalence principle at the recombination time. PACS numbers: 98.80.Es, 04.80.Cc, 98.70.Vc, 98.80.Ft
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Papers by Vincent Boucher
First of all, we propose a generic test seeking for possible Newton’s constant variations in the primeval plasma. The modified weight of baryons translates the equilibrium point of the acoustic oscillations. A constraint on the amplitude of such variations is extracted from the anisotropies of the cosmic microwave background.
Secondly, we scrutinize a simple modification of general relativity providing a minimal violation of the strong equivalence principle. Although the additional scalar field acts as a dark radiation at the cosmological expansion level, the imprint left on the matter field perturbations is clearly distinguishable from other radiations because of the particular scalar field anisotropic stress. Several constraints for this alternative gravitational theory are derived from the analysis of the cosmic microwave background, Type Ia supernovae and the measure of the Lemaître-Hubble constant.
Finally, we replace the cosmological constant by a quintessence field. For selected realistic models agreeing with current cosmological data, it is shown that the non-linear processes driving the growth of matter’s large scale structures encode the nature and the dynamics of dark energy.
Although the confrontation between the investigated alternative models and available cosmological data currently does not raise deviation to the concordant ΛCDM model, the present study shows that predictions and signatures of these models are unique compared to the standard scenario.
First of all, we propose a generic test seeking for possible Newton’s constant variations in the primeval plasma. The modified weight of baryons translates the equilibrium point of the acoustic oscillations. A constraint on the amplitude of such variations is extracted from the anisotropies of the cosmic microwave background.
Secondly, we scrutinize a simple modification of general relativity providing a minimal violation of the strong equivalence principle. Although the additional scalar field acts as a dark radiation at the cosmological expansion level, the imprint left on the matter field perturbations is clearly distinguishable from other radiations because of the particular scalar field anisotropic stress. Several constraints for this alternative gravitational theory are derived from the analysis of the cosmic microwave background, Type Ia supernovae and the measure of the Lemaître-Hubble constant.
Finally, we replace the cosmological constant by a quintessence field. For selected realistic models agreeing with current cosmological data, it is shown that the non-linear processes driving the growth of matter’s large scale structures encode the nature and the dynamics of dark energy.
Although the confrontation between the investigated alternative models and available cosmological data currently does not raise deviation to the concordant ΛCDM model, the present study shows that predictions and signatures of these models are unique compared to the standard scenario.