Overview Surveys

Overview Surveys - Nikhil Padmanabhan

Nikhil Padmanabhan
September 24, 2015
The interpretation of low-redshift galaxy surveys is more complicated than the interpretation of CMB temperature anisotropies. First, the matter distribution evolves nonlinearly at low redshift, limiting the use of perturbative methods. Secondly, we observe galaxies, rather than the underlying matter field. Fortunately, considerable progress has been made in understanding the large-scale structure of galaxies. A key insight has been that galaxies form in bound structures called halos, whose statistics (e.g. abundance, clustering, etc.) govern the observed statistics of galaxies. For example, bias models are often used to describe the relation between collapsed, virialized objects and the underlying matter distribution; such bias models are a key element of Large Scale Structure data analysis. Over the last couple of years, however, it has become clear that the simplest bias models can describe neither data nor simulations to the desired percent level precision. The simplest, most widely used approaches study the clustering properties only as a function of halo mass, thereby ignoring the other properties like concentration, merger history, formation time etc. The dependence of clustering properties on these additional variables is known as assembly bias; accounting for it is required if inferences from clustering are to be unbiased. Recent progress in this field suggests that a deeper understanding of how the clustering depends on other physical quantities has the potential to uncover new measurables for addressing fundamental physics questions as well as for understanding galaxy formation.
During the workshop, we plan to discuss the following issues of the biasing:
Assembly Bias
Extended Press-Schechter and Peaks formalism
Perturbative Descriptions and Effective Field Theory, Relation to Galaxy Formation
Requirements for upcoming surveys
The planned format of the workshop consists of a small number of overview talks, some expert introductions on specific subjects and extended discussions of the status of the field, recent developments and the broader goals and directions for future research.
This workshop is sponsored by the Department of Astrophysical Sciences and the Institute for Advanced Study.