254 research outputs found
Topology of Large-Scale Structure by Galaxy Type: Hydrodynamic Simulations
The topology of large scale structure is studied as a function of galaxy type
using the genus statistic. In hydrodynamical cosmological CDM simulations,
galaxies form on caustic surfaces (Zeldovich pancakes) then slowly drain onto
filaments and clusters. The earliest forming galaxies in the simulations
(defined as ``ellipticals") are thus seen at the present epoch preferentially
in clusters (tending toward a meatball topology), while the latest forming
galaxies (defined as ``spirals") are seen currently in a spongelike topology.
The topology is measured by the genus (= number of ``donut" holes - number of
isolated regions) of the smoothed density-contour surfaces. The measured genus
curve for all galaxies as a function of density obeys approximately the
theoretical curve expected for random-phase initial conditions, but the early
forming elliptical galaxies show a shift toward a meatball topology relative to
the late forming spirals. Simulations using standard biasing schemes fail to
show such an effect. Large observational samples separated by galaxy type could
be used to test for this effect.Comment: Princeton University Observatory, submitted to The Astrophysical
Journal, figures can be ftp'ed from ftp://astro.princeton.edu/cen/TOP
Using the Topology of Large Scale Structure to constrain Dark Energy
The use of standard rulers, such as the scale of the Baryonic Acoustic
oscillations (BAO), has become one of the more powerful techniques employed in
cosmology to probe the entity driving the accelerating expansion of the
Universe. In this paper, the topology of large scale structure (LSS) is used as
one such standard ruler to study this mysterious `dark energy'. By following
the redshift evolution of the clustering of luminous red galaxies (LRGs) as
measured by their 3D topology (counting structures in the cosmic web), we can
chart the expansion rate and extract information about the equation of state of
dark energy. Using the technique first introduced in (Park & Kim, 2009), we
evaluate the constraints that can be achieved using 3D topology measurements
from next-generation LSS surveys such as the Baryonic Oscillation Spectroscopic
Survey (BOSS). In conjunction with the information that will be available from
the Planck satellite, we find a single topology measurement on 3 different
scales is capable of constraining a single dark energy parameter to within 5%
and 10% when dynamics are permitted. This offers an alternative use of the data
available from redshift surveys and serves as a cross-check for BAO studies.Comment: 8 pages, 5 figures, 2 tables, Submitted to MNRAS, updated
acknowledgement
- …