2,579 research outputs found
Multiple Uncertainties in Time-Variant Cosmological Particle Data
Though the mediums for visualization are limited, the potential dimensions of a dataset are not. In many areas of scientific study, understanding the correlations between those dimensions and their uncertainties is pivotal to mining useful information from a dataset. Obtaining this insight can necessitate visualizing the many relationships among temporal, spatial, and other dimensionalities of data and its uncertainties. We utilize multiple views for interactive dataset exploration and selection of important features, and we apply those techniques to the unique challenges of cosmological particle datasets. We show how interactivity and incorporation of multiple visualization techniques help overcome the problem of limited visualization dimensions and allow many types of uncertainty to be seen in correlation with other variables
Sterile neutrinos with eV masses in cosmology -- how disfavoured exactly?
We study cosmological models that contain sterile neutrinos with eV-range
masses as suggested by reactor and short-baseline oscillation data. We confront
these models with both precision cosmological data (probing the CMB decoupling
epoch) and light-element abundances (probing the BBN epoch). In the minimal
LambdaCDM model, such sterile neutrinos are strongly disfavoured by current
data because they contribute too much hot dark matter. However, if the
cosmological framework is extended to include also additional relativistic
degrees of freedom -- beyond the three standard neutrinos and the putative
sterile neutrinos, then the hot dark matter constraint on the sterile states is
considerably relaxed. A further improvement is achieved by allowing a dark
energy equation of state parameter w<-1. While BBN strongly disfavours extra
radiation beyond the assumed eV-mass sterile neutrino, this constraint can be
circumvented by a small nu_e degeneracy. Any model containing eV-mass sterile
neutrinos implies also strong modifications of other cosmological parameters.
Notably, the inferred cold dark matter density can shift up by 20 to 75%
relative to the standard LambdaCDM value.Comment: 14 pages, 6 figures, v2: minor changes, matches version accepted for
publication in JCA
Report from the Tri-Agency Cosmological Simulation Task Force
The Tri-Agency Cosmological Simulations (TACS) Task Force was formed when
Program Managers from the Department of Energy (DOE), the National Aeronautics
and Space Administration (NASA), and the National Science Foundation (NSF)
expressed an interest in receiving input into the cosmological simulations
landscape related to the upcoming DOE/NSF Vera Rubin Observatory (Rubin),
NASA/ESA's Euclid, and NASA's Wide Field Infrared Survey Telescope (WFIRST).
The Co-Chairs of TACS, Katrin Heitmann and Alina Kiessling, invited community
scientists from the USA and Europe who are each subject matter experts and are
also members of one or more of the surveys to contribute. The following report
represents the input from TACS that was delivered to the Agencies in December
2018.Comment: 36 pages, 3 figures. Delivered to NASA, NSF, and DOE in Dec 201
A Comprehensive Analysis of Uncertainties Affecting the Stellar Mass - Halo Mass Relation for 0<z<4
We conduct a comprehensive analysis of the relationship between central
galaxies and their host dark matter halos, as characterized by the stellar
mass-halo mass (SM-HM) relation, with rigorous consideration of uncertainties.
Our analysis focuses on results from the abundance matching technique, which
assumes that every dark matter halo or subhalo above a specific mass threshold
hosts one galaxy. We discuss the quantitative effects of uncertainties in
observed galaxy stellar mass functions (GSMFs) (including stellar mass
estimates and counting uncertainties), halo mass functions (including cosmology
and uncertainties from substructure), and the abundance matching technique used
to link galaxies to halos (including scatter in this connection). Our analysis
results in a robust estimate of the SM-HM relation and its evolution from z=0
to z=4. The shape and evolution are well constrained for z < 1. The largest
uncertainties at these redshifts are due to stellar mass estimates; however,
failure to account for scatter in stellar masses at fixed halo mass can lead to
errors of similar magnitude in the SM-HM relation for central galaxies in
massive halos. We also investigate the SM-HM relation to z=4, although the
shape of the relation at higher redshifts remains fairly unconstrained when
uncertainties are taken into account. These results will provide a powerful
tool to inform galaxy evolution models. [Abridged]Comment: 27 pages, 12 figures, updated to match ApJ accepted version
Are galaxies extending?
It is suggested that the recently observed size evolution of very massive
compact galaxies in the early universe can be explained, if dark matter is in
Bose Einstein condensate.
In this model the size of the dark matter halos and galaxies depends on the
correlation length of dark matter and, hence, on the the expansion of the
universe. This theory predicts that the size of the galaxies increases as the
Hubble radius of the universe even without merging, which agrees well with the
recent observational data.Comment: 5 pages, 2figs, revtex,accepted version for PL
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