The clustering of critical points in the evolving cosmic web (original) (raw)

2020, arXiv: Cosmology and Nongalactic Astrophysics

Focusing on both small separations and Baryonic Acoustic Oscillation scales, the cosmic evolution of the clustering properties of peak, void, wall, and filament-type critical points is measured using two-point correlation functions in Lambda\LambdaLambdaCDM dark matter simulations as a function of their relative rarity. A qualitative comparison to the corresponding theory for Gaussian Random fields allows us to understand the following observed features: i) the appearance of an exclusion zone at small separation, whose size depends both on rarity and on the signature (\ie the number of negative eigenvalues) of the critical points involved; ii) the amplification of the Baryonic Acoustic Oscillation bump with rarity and its reversal for cross-correlations involving negatively biased critical points; iii) the orientation-dependent small-separation divergence of the cross-correlations of peaks and filaments (voids and walls) which reflects the relative loci of such points in the filament's (w...

Free PDF

When do cosmic peaks, filaments or walls merge? A theory of critical events in a multi-scale landscape

Monthly Notices of the Royal Astronomical Society, 2020

The merging rate of cosmic structures is computed, relying on the Ansatz that they can be predicted in the initial linear density field from the coalescence of critical points with increasing smoothing scale, used here as a proxy for cosmic time. Beyond the mergers of peaks with saddle points (a proxy for halo mergers), we consider the coalescence and nucleation of all sets of critical points, including wall-saddle to filament-saddle and wall-saddle to minima (a proxy for filament and void mergers respectively), as they impact the geometry of galactic infall, and in particular filament disconnection. Analytical predictions of the one-point statistics are validated against multiscale measurements in 2D and 3D realisations of Gaussian random fields (the corresponding code being available upon request) and compared qualitatively to cosmological N-body simulations at early times (z ≥ 10) and large scales (≥ 5Mpc/h). The rate of filament coalescence is compared to the merger rate of halo...

Free PDF

Dark Matter and the Cosmic Web revised.pdf

The cosmic web is a filament like structure that connects galaxies. It is imaged by gravitational lensing and is thought to be composed mainly of dark matter since it is very faint in the electromagnetic spectrum. There are computer simulations of the web showing that galaxies are often nodes for multiple branches. https://www.youtube.com/watch?v=ivymdduulFU . Conversely there are volumes in the sky that are relatively devoid of matter. However, cosmologists have long recognized that mass is uniform [18][21] at a scale much larger than the web. Scientists are trying to understand dark matter and dark energy [20]. The unexpected web like structure adds to a list of cosmology unknowns. The author studied mass accumulation [16] with an expansion model associated with energy values and relationships found in the proton model [Appendix 1]. WMAP [17][19] and later the PLANCK satellites measured cosmic background radiation anisotropy and concluded that there are scale invariant density variations on the order of d’/d=8e-6. The author used this data to predict mass accumulation in three primary levels of structure. It appears that stars, within galaxies within galaxy clusters all result from differential central mass related to measured density variations. Surrounding density is accelerated toward the central mass and densified by radius reduction that obeys a R*v^2=r*V^2 conservation law. Simulations presented agree with several observations including when stars light up, the orbital velocity of stars and Hubble’s constant [15]. This paper takes the simulations one step further by studying the shape of the structure. This paper provides a reasonable explanation for the cosmic web without assuming dark matter [8][12]. Falling mass develops a preferred orientation that changes the shape of the mass, lengthening it into filaments rather than spheres. This is like our atmosphere that forms tornados when there are density differences. In this case, the density difference is the central mass of the star volume. As mass falls toward the central density, it contracts and spins extending the filament outward from the central mass. Simulations of these structures extend between mass accumulating in adjacent areas and appear to be the feature being imaged as the cosmic web. A realistic looking simulation of a barred spiral galaxy is included.

Free PDF

Correlation function: biasing and fractal properties of the cosmic web

Astronomy & Astrophysics

Aims. Our goal is to determine how the spatial correlation function of galaxies describes biasing and fractal properties of the cosmic web. Methods. We calculated spatial correlation functions of galaxies, ξ(r), structure functions, g(r) = 1 + ξ(r), gradient functions, γ(r) = d log g(r)/d log r, and fractal dimension functions, D(r) = 3 + γ(r), using dark matter particles of the biased Λ cold dark matter (CDM) simulation, observed galaxies of the Sloan Digital Sky Survey (SDSS), and simulated galaxies of the Millennium and EAGLE simulations. We analysed how these functions describe fractal and biasing properties of the cosmic web. Results. The correlation functions of the biased ΛCDM model samples at small distances (particle and galaxy separations), r ≤ 2.25 h−1 Mpc, describe the distribution of matter inside dark matter halos. In real and simulated galaxy samples, only the brightest galaxies in clusters are visible, and the transition from clusters to filaments occurs at a distanc...

Free PDF

$Correlation function: biasing and fractal properties of the cosmic web Cover Page$

Dark Matter and the Cosmic Web revised

The cosmic web is a filament like structure that connects galaxies. It is imaged by gravitational lensing and is thought to be composed mainly of dark matter since it is very faint in the electromagnetic spectrum. There are computer simulations of the web showing that galaxies are often nodes for multiple branches. https://www.youtube.com/watch?v=ivymdduulFU. Conversely there are volumes in the sky that are relatively devoid of matter. However, cosmologists have long recognized that mass is uniform [18][21] at a scale much larger than the web. Scientists are trying to understand dark matter and dark energy [20]. The unexpected web like structure adds to a list of cosmology unknowns. The author studied mass accumulation [16] with an expansion model associated with energy values and relationships found in the proton model [Appendix 1]. WMAP [17][19] and later the PLANCK satellites measured cosmic background radiation anisotropy and concluded that there are scale invariant density variations on the order of d'/d=8e-6. The author used this data to predict mass accumulation in three primary levels of structure. It appears that stars, within galaxies within galaxy clusters all result from differential central mass related to measured density variations. Surrounding density is accelerated toward the central mass and densified by radius reduction that obeys a R*v^2=r*V^2 conservation law. Simulations presented agree with several observations including when stars light up, the orbital velocity of stars and Hubble's constant [15]. This paper takes the simulations one step further by studying the shape of the structure. This paper provides a reasonable explanation for the cosmic web without assuming dark matter [8][12]. Falling mass develops a preferred orientation that changes the shape of the mass, lengthening it into filaments rather than spheres. This is like our atmosphere that forms tornados when there are density differences. In this case, the density difference is the central mass of the star volume. As mass falls toward the central density, it contracts and spins extending the filament outward from the central mass. Simulations of these structures extend between mass accumulating in adjacent areas and appear to be the feature being imaged as the cosmic web. A realistic looking simulation of a barred spiral galaxy is included. Relationships that partition volumes into clusters, galaxies, and stars At decoupling (decoupling is the condition that clears the plasma), clusters of galaxies and galaxies of stars have specific relationships to extremely long waves. These waves subdivide an overall sphere (and its associated mass) into smaller and smaller volumes.

Free PDF