8 research outputs found
Filament and Shape Statistics: A Quantitative Comparison of Cold + Hot and Cold Dark Matter Cosmologies vs. CfA1 Data
A new class of geometric statistics for analyzing galaxy catalogs is
presented. Filament statistics quantify filamentarity and planarity in large
scale structure in a manner consistent with catalog visualizations. These
statistics are based on sequences of spatial links which follow local
high-density structures. From these link sequences we compute the discrete
curvature, planarity, and torsion. Filament statistics are applied to CDM and
CHDM () simulations of Klypin \etal (1996), the CfA1-like
mock redshift catalogs of Nolthenius, Klypin and Primack (1994, 1996), and the
CfA1 catalog. We also apply the moment-based shape statistics developed by
Babul \& Starkman (1992), Luo \& Vishniac (1995), and Robinson \& Albrecht
(1996) to these same catalogs, and compare their robustness and discriminatory
power versus filament statistics. For 100 Mpc periodic simulation boxes ( km s Mpc), we find discrimination of (where
represents resampling errors) between CHDM and CDM for selected
filament statistics and shape statistics, including variations in the galaxy
identification scheme. Comparing the CfA1 data versus the models does not yield
a conclusively favored model; no model is excluded at more than a level for any statistic, not including cosmic variance which could
further degrade the discriminatory power. We find that CfA1 discriminates
between models poorly mainly due to its sparseness and small number of
galaxies, not due to redshift distortion, magnitude limiting, or geometrical
effects. We anticipate that the proliferation of large redshift surveys and
simulations will enable the statistics presented here to provide robust
discrimination between large-scale structure in various cosmological models.Comment: 17 pages, 12 figures, LaTex (uses mn.sty). Accepted by MNRA
Dark Matter Halo Properties vs. Local Density and Cosmic Web Location
We study the effects of the local environmental density and the cosmic web
environment (filaments, walls, and voids) on key properties of dark matter
halos using the Bolshoi-Planck LCDM cosmological simulation. The z = 0
simulation is analysed into filaments, walls, and voids using the SpineWeb
method and also the VIDE package of tools, both of which use the watershed
transform. The key halo properties that we study are the specific mass
accretion rate, spin parameter, concentration, prolateness, scale factor of the
last major merger, and scale factor when the halo had half of its z = 0 mass.
For all these properties, we find that there is no discernible difference
between the halo properties in filaments, walls, or voids when compared at the
same environmental density. As a result, we conclude that environmental density
is the core attribute that affects these properties. This conclusion is in line
with recent findings that properties of galaxies in redshift surveys are
independent of their cosmic web environment at the same environmental density
at z ~ 0. We also find that the local web environment of the Milky Way and the
Andromeda galaxies near the centre of a cosmic wall does not appear to have any
effect on the properties of these galaxies' dark matter halos except for their
orientation, although we find that it is rather rare to have such massive halos
near the centre of a relatively small cosmic wall.Comment: 23 page
The job crisis in Latin America: A role for multinational corporations in introducing more labour-intensive technologies
Halo and subhalo demographics with Planck cosmological parameters: Bolshoi–Planck and MultiDark–Planck simulations
Clustering and halo abundances in early dark energy cosmological models
Cold Dark Matter with cosmological constant (ΛCDM) cosmological models with early dark energy (EDE) have been proposed to resolve tensions between the Hubble constant H 0=100, h km -1pc-1 measured locally, giving h ≈ 0.73, and H0 deduced from Planck cosmic microwave background (CMB) and other early-Universe measurements plus ΛCDM, giving h ≈ 0.67. EDE models do this by adding a scalar field that temporarily adds dark energy equal to about 10 per cent of the cosmological energy density at the end of the radiation-dominated era at redshift z ∼3500. Here, we compare linear and non-linear predictions of a Planck-normalized ΛCDM model including EDE giving h = 0.728 with those of standard Planck-normalized ΛCDM with h = 0.678. We find that non-linear evolution reduces the differences between power spectra of fluctuations at low redshifts. As a result, at z = 0 the halo mass functions on galactic scales are nearly the same, with differences only 1-2 per cent. However, the differences dramatically increase at high redshifts. The EDE model predicts 50 per cent more massive clusters at z = 1 and twice more galaxy-mass haloes at z = 4. Even greater increases in abundances of galaxy-mass haloes at higher redshifts may make it easier to reionize the universe with EDE. Predicted galaxy abundances and clustering will soon be tested by the James Webb Space Telescope (JWST) observations. Positions of baryonic acoustic oscillations (BAOs) and correlation functions differ by about 2 per cent between the models-an effect that is not washed out by non-linearities. Both standard ΛCDM and the EDE model studied here agree well with presently available acoustic-scale observations, but the Dark Energy Spectroscopic Instrument and Euclid measurements will provide stringent new tests. © 2021 The Author(s).AK and FP thank the support of the Spanish Ministry of Science funding grant PGC2018-101931-B-I00. This work used the skun6@IAA facility managed by the Instituto de AstrofÃsica de AndalucÃa (CSIC). The equipment was funded by the Spanish Ministry of Science EU-FEDER infrastructure grantEQC2018-004366-P. MK acknowledges the support of NSF Grant No. 1519353, NASA NNX17AK38G, and the Simons Foundation. TLS acknowledges support from NASA (through grant 80NSSC18K0728) and the Research Corporation. We thank Alexie Leauthaud and Johannes Lange for a helpful discussion about weak lensing results.With funding from the Spanish government through the Severo Ochoa Centre of Excellence accreditation SEV-2017-0709.Peer reviewe