Tidal alignment of galaxies
- Center for Cosmology and AstroParticle Physics, Department of Physics, The Ohio State University, Columbus, OH (United States)
- Stanford Institute for Theoretical Physics and Department of Physics, Stanford University, Stanford, CA (United States)
- Departments of Physics and Astronomy and Lawrence Berkeley National Laboratory, University of California, Berkeley, CA (United States)
We develop an analytic model for galaxy intrinsic alignments (IA) based on the theory of tidal alignment. We calculate all relevant nonlinear corrections at one-loop order, including effects from nonlinear density evolution, galaxy biasing, and source density weighting. Contributions from density weighting are found to be particularly important and lead to bias dependence of the IA amplitude, even on large scales. This effect may be responsible for much of the luminosity dependence in IA observations. The increase in IA amplitude for more highly biased galaxies reflects their locations in regions with large tidal fields. We also consider the impact of smoothing the tidal field on halo scales. We compare the performance of this consistent nonlinear model in describing the observed alignment of luminous red galaxies with the linear model as well as the frequently used 'nonlinear alignment model,' finding a significant improvement on small and intermediate scales. We also show that the cross-correlation between density and IA (the 'GI' term) can be effectively separated into source alignment and source clustering, and we accurately model the observed alignment down to the one-halo regime using the tidal field from the fully nonlinear halo-matter cross correlation. Inside the one-halo regime, the average alignment of galaxies with density tracers no longer follows the tidal alignment prediction, likely reflecting nonlinear processes that must be considered when modeling IA on these scales. Finally, we discuss tidal alignment in the context of cosmic shear measurements.
- OSTI ID:
- 22525617
- Journal Information:
- Journal of Cosmology and Astroparticle Physics, Vol. 2015, Issue 08; Other Information: Country of input: International Atomic Energy Agency (IAEA); ISSN 1475-7516
- Country of Publication:
- United States
- Language:
- English
Similar Records
Intrinsic alignment-lensing interference as a contaminant of cosmic shear
Alignments of dark matter halos with large-scale tidal fields: mass and redshift dependence