Mathematics – Logic
Scientific paper
Jan 2011
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2011aas...21720405f&link_type=abstract
American Astronomical Society, AAS Meeting #217, #204.05; Bulletin of the American Astronomical Society, Vol. 43, 2011
Mathematics
Logic
Scientific paper
Reconstruction has been shown to restore the Baryon Acoustic Oscillation (BAO) peak after it has been degraded by nonlinear structure formation, thereby increasing the precision of the measurement, especially at low redshift. We investigate improving the BAO reconstruction method using a logarithmic approximation of the Lagrangian displacement, instead of the linear Zel'dovich displacement, by calculating the divergence of the displacement field directly in a cosmological nbody simulation. We explore several ways of calculating the divergence and density and discuss their relative merits and shortcomings. We show that the logarithmic approximation holds well into the nonlinear regime, allowing a smaller scale smoothing of the density field in the reconstruction algorithm and thus increasing its effectiveness.
Traditionally a mass particle is thought to enter the nonlinear regime at shell-crossing, where the linear Zel'dovich approximation is no longer valid; the particle will undergo many such crossings as it settles into a halo. We introduce a novel halo-finding algorithm dubbed ORIGAMI that tags halo particles in a simulation according to whether they have crossed paths with their Lagrangian neighbors in a set of orthogonal axes. This gives a definition of halo particles that is independent of a density cutoff, though the grouping of particles into specific halos requires additional refinement. ORIGAMI performs well compared to the standard halo finders and can be extended to a full morphology tagger (halos, filaments, walls, and voids) or act as the first step in another halo grouping algorithm.
The authors are grateful for support from the Gordon and Betty Moore and the W.M. Keck Foundations.
Falck Bridget
Neyrinck Mark C.
Szalay Alex S.
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