Beecroft Institute for Particle Astrophysics and Cosmology

Abstract:

We report on two quantitative, morphological estimators of the filamentary structure of the Cosmic Web, the so-called global and local skeletons. The first, based on a global study of the matter density gradient flow, allows us to study the connectivity between a density peak and its surroundings, with direct relevance to the anisotropic accretion via cold flows on galactic halos. From the second, based on a local constraint equation involving the derivatives of the field, we can derive predictions for powerful statistics, such as the differential length and the relative saddle to extrema counts of the Cosmic web as a function of density threshold (with application to percolation of structures and connectivity), as well as a theoretical framework to study their cosmic evolution through the onset of gravity-induced non-linearities. © 2010 American Institute of Physics.

Abstract:

Morphology is a powerful indicator of a galaxy's dynamical and merger history. It is strongly correlated with many physical parameters, including mass, star formation history and the distribution of mass. The Galaxy Zoo project collected simple morphological classifications of nearly 900,000 galaxies drawn from the Sloan Digital Sky Survey, contributed by hundreds of thousands of volunteers. This large number of classifications allows us to exclude classifier error, and measure the influence of subtle biases inherent in morphological classification. This paper presents the data collected by the project, alongside measures of classification accuracy and bias. The data are now publicly available and full catalogues can be downloaded in electronic format from http://data.galaxyzoo.org.

Abstract:

We propose a novel method for the extraction of the baryonic acoustic oscillation scale in galaxy photometric surveys. The evolution of this scale can be used as a standard ruler in order to constrain cosmological parameters. The method consists in parametrize the angular correlation function ω(θ), with a simple analitical expresion, in order to extract the sound horizon scale. The method has been tested in the MICE simulation, one of the largest N-body simulation to date. We have considered projection effects, non-linearities and observational effects in our analysis, obtaining errors in cosmological parameters in agreement with what is expected in new generation surveys.