Astrophysical Tests of Modified Gravity: A Screening Map of the Nearby Universe

TL;DR

This paper develops a 3D screening map of the nearby universe using N-body simulations and observational data to test modified gravity theories, enabling new astrophysical tests of gravity in different environments.

Contribution

It introduces a method to create a comprehensive screening map for the nearby universe, combining simulations and observations for testing modified gravity theories.

Findings

Created a 3D screening map out to 200 Mpc in SDSS footprint.

Calibrated simple approximations for screening levels using simulations.

Estimated systematic errors and observational contamination effects.

Abstract

Astrophysical tests of modified modified gravity theories in the nearby universe have been emphasized recently by Hui, Nicolis and Stubbs (2009) and Jain and VanderPlas (2011). A key element of such tests is the screening mechanism whereby general relativity is restored in massive halos or high density environments like the Milky Way. In chameleon theories of gravity, including all f(R) models, field dwarf galaxies may be unscreened and therefore feel an extra force, as opposed to screened galaxies. The first step to study differences between screened and unscreened galaxies is to create a 3D screening map. We use N-body simulations to test and calibrate simple approximations to determine the level of screening in galaxy catalogs. Sources of systematic errors in the screening map due to observational inaccuracies are modeled and their contamination is estimated. We then apply our methods to create a map out to 200 Mpc in the Sloan Digital Sky Survey footprint using data from the Sloan survey and other sources. In two companion papers this map will be used to carry out new tests of gravity using distance indicators and the disks of dwarf galaxies. We also make our screening map publicly available.