The absence of a physically motivated model for large scale profiles of cosmic voids limits our ability to extract valuable cosmological information from their study. In this paper, we address this problem by introducing the spherically compensated cosmic regions, named CoSpheres. Such cosmic regions are identified around local extrema in the density field and admit a unique compensation radius $R_1$ where the internal spherical mass is exactly compensated. Their origin is studied by extending the standard peak model and implementing the compensation condition. Since the compensation radius evolves as the Universe itself, $R_1(t)\propto a(t)$, CoSpheres behave as bubble Universes with fixed comoving volume. Using the spherical collapse model, we reconstruct their profiles with a very high accuracy until $z=0$ in N-body simulations. CoSpheres are symmetrically defined and reconstructed for both central maximum (seeding haloes and galaxies) and minimum (identified with cosmic voids). We show that the full non linear dynamics can be solved analytically around this particular compensation radius, providing useful predictions for cosmology. This formalism highlights original correlations between local extremum and their large scale cosmic environment. The statistical properties of these spherically compensated cosmic regions and the possibilities to constrain efficiently both cosmology and gravity will be investigated in companion papers.
The statistical properties of cosmic structures are well known to be strong probes for cosmology. In particular, several studies tried to use the cosmic void counting number to obtain tight constrains on Dark Energy. In this paper we address this question by using the CoSphere model as introduced in de Fromont & Alimi (2017a). We derive their exact statistics in both primordial and non linearly evolved Universe for the standard $Λ$CDM model. We first compute the full joint Gaussian probability distribution for the various parameters describing these profiles in the Gaussian Random Field. We re…
We present the first determination of the intrinsic triaxial shapes and tree-dimensional physical parameters of both dark matter (DM) and intra-cluster medium (ICM) for the galaxy cluster Abell 1689. We exploit the novel method we recently introduced (Morandi et al. 2010) in order to infer the tree-dimensional physical properties in triaxial galaxy clusters by combining jointly X-ray and strong lensing data. We find that Abell 1689 can be modeled as a triaxial galaxy cluster with DM halo axial ratios 1.24 +/- 0.13 and 2.37 +/- 0.11 on the plane of the sky and along the line of sight, respectiv…
The possibility of reconstructing a spherically symmetric inhomogeneous Lemaitre-Tolman-Bondi (LTB) model with $Λ$CDM observations has drawn a lot of attention. Recently, a LTB model having the same luminosity-distance and light-cone mass density as the $Λ$CDM model was reconstructed. We calculate the cosmic age at our position in this model, and get the age $t_{LTB}<11.7$Gyr in 2$σ$ confidence level from the Seven-Year WMAP observations. This result is inconsistent with some Milky Way observations.
In this work, we use a combined approach of Hubble parameter data together with redshift-space-distortion $(fσ_8)$ data, which together are used to reconstruct the teleparallel gravity (TG) Lagrangian via Gaussian processes (GP). The adopted Hubble data mainly comes from cosmic chronometers, while for the Type Ia supernovae data we use the latest jointly calibrated Pantheon compilation. Moreover, we consider two main GP covariance functions, namely the squared-exponential and Cauchy kernels in order to show consistency (to within 1$σ$ uncertainties). The core results of this work are the numer…
Reconstructing the cosmic expansion with a generalized q(z) parameterization: A decelerating Universe from late-time constraints
Instituto de Astronomía, Observatorio Astronómico Nacional, Universidad Nacional Autónoma de México（墨西哥国立自治大学国家天文台天文学研究所）；Facultad de Ingeniería, Universidad Autónoma de Querétaro（克雷塔罗自治大学工程学院）；Depto. de Física y Matemáticas, Universidad Iberoamericana Ciudad de México（墨西哥伊比利亚美洲大学物理与数学系）；Instituto de Física y Astronomía, Universidad de Valparaíso（瓦尔帕莱索大学物理与天文学研究所）；Escuela de Ingeniería, Universidad Central de Chile（智利中央大学工程学院）
We present a nonparametric approach to reconstruct the interaction between dark energy and dark matter directly from SNIa Union 2.1 data using Gaussian processes, which is a fully Bayesian approach for smoothing data. In this method, once the equation of state ($w$) of dark energy is specified, the interaction can be reconstructed as a function of redshift. For the decaying vacuum energy case with $w=-1$, the reconstructed interaction is consistent with the standard $Λ$CDM model, namely, there is no evidence for the interaction. This also holds for the constant $w$ cases from $-0.9$ to $-1.1$ …
EFT of Dark Energy with Cosmic Chronometers: Reconstructing Background EFT Functions
Department of Physics, College of Humanities and Sciences, Nihon University（日本大学人文科学系）；Center for Gravitational Physics and Quantum Information, Yukawa Institute for Theoretical Physics, Kyoto University（京都大学汤川理论物理研究所引力物理与量子信息中心）
Gamma-ray bursts (GRBs) have been regarded as standard candles at very high redshift for cosmology research. We have proposed a new method to calibrate GRB distance indicators with Type Ia supernova (SNe Ia) data in a completely cosmology-independent way to avoid the circularity problem that had limited the direct use of GRBs to probe cosmology [N. Liang, W. K. Xiao, Y. Liu, and S. N. Zhang, Astrophys. J. 685, 354 (2008).]. In this paper, a simple method is provided to combine GRB data into the joint observational data analysis to constrain cosmological models; in this method those SNe Ia data…
Supermassive black hole seeds from direct collapse of CDM-curvature peaks
University of Canterbury（坎特伯雷大学）；Institute of Cosmology & Gravitation, University of Portsmouth（朴茨茅斯大学宇宙学与引力研究所）；INFN Sezione di Trieste（的里雅斯特意大利国家核物理研究所）；Rikkyo University（立教大学）；iCLA, Yamanashi Gakuin University（山梨学院大学国际基督教学习中心）；Centre for Theoretical Physics, Jamia Millia Islamia（贾米亚米利亚伊斯兰大学理论物理中心）
The Universe's initial conditions, in particular baryon and cold dark matter (CDM) isocurvature perturbations, are poorly constrained on sub-Mpc scales. In this paper, we develop a new formalism to compute the effect of small-scale baryon perturbations on the mean free-electron abundance, thus on cosmic microwave background (CMB) anisotropies. Our framework can accommodate perturbations with arbitrary time and scale dependence. We apply this formalism to four different combinations of baryon and CDM isocurvature modes, and use Planck CMB-anisotropy data to probe their initial amplitude. We fin…
KAN-LSTM-Transformer Neural Networks, MFV and Cosmological Parameters
School of Basic Sciences, Tianjin Agricultural University（天津农学院基础科学学院）；Physics Experimental Center, Department of Mathematics and Physics, Hebei GEO University（河北地质大学数学与物理系物理实验中心）；Hebei Key Laboratory of Optoelectronic Information and Geo-detection Technology, Hebei GEO University（河北地质大学河北省光电信息与地球探测技术重点实验室）
We compare model results from a semi-analytic (merger-tree based) framework for high-redshift (z ~ 5-20) galaxy formation against reionization indicators, including the Planck electron scattering optical depth and the ionizing photon emissivity, to shed light on the reionization history and sources in Cold (CDM) and Warm Dark Matter (WDM; particle masses of $m_x = 1.5,3$ and 5 keV) cosmologies. This model includes all the key processes of star formation, supernova feedback, the merger/accretion/ejection driven evolution of gas and stellar mass and the effect of the ultra-violet background (UVB…
We measure the average temperature decrement on the cosmic microwave background (CMB) produced by voids selected in the SDSS DR7 spectroscopic redshift galaxy catalog, spanning redshifts $0<z<0.44$. We find an imprint of amplitude between 2.6 and 2.9$μK$ as viewed through a compensated top-hat filter scaled to the radius of each void; we assess the statistical significance of the imprint at ~2$σ$. We make crucial use of $N$-body simulations to calibrate our analysis. As expected, we find that large voids produce cold spots on the CMB through the Integrated Sachs-Wolfe (ISW) effect. However, we…
Small temperature anisotropies in the Cosmic Microwave Background can be sourced by density perturbations via the late-time integrated Sachs-Wolfe effect. Large voids and superclusters are excellent environments to make a localized measurement of this tiny imprint. In some cases excess signals have been reported. We probed these claims with an independent data set, using the first year data of the Dark Energy Survey in a different footprint, and using a different super-structure finding strategy. We identified 52 large voids and 102 superclusters at redshifts $0.2 < z < 0.65$. We used the Jubi…
The free-streaming length of dark matter from JWST observations of 28 strong gravitational lenses
University of Chicago（芝加哥大学）；University of California, Merced（加州大学默塞德分校）；University of California, Los Angeles（加州大学洛杉矶分校）；University of California, Irvine（加州大学尔湾分校）；Universidad Andres Bello（安德斯·贝略大学）；California Polytechnic State University（加州州立理工大学）；Carnegie Institution for Science（卡内基科学机构）；Stony Brook University（石溪大学）；California Institute of Technology（加州理工学院）；University of Southampton（南安普顿大学）
A number of independent observations suggest that the intergalactic medium was significantly neutral at $z=7$ and that reionization was, perhaps, still in progress at $z=5.7$. The narrowband survey, SILVERRUSH, has mapped over $2,000$ Lyman-$α$ emitters (LAEs) at these redshifts. Previous analyses have assumed that reionization was over by $z=5.7$, but this data may actually sample the final stages of reionization when the last neutral islands were relegated to the cosmic voids. Motivated by these developments, we reexamine LAE void and peak statistics and their ability to constrain reionizati…
