A halo model for intrinsic alignments of galaxy ellipticities

By M. Schneider, Sarah Bridle. 2009

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Correlations between intrinsic ellipticities of galaxies are a potentially important systematic error when constraining dark energy properties from weak gravitational lensing (cosmic shear) surveys. In the absence of perfectly known galaxy redshifts, some modelling of the galaxy intrinsic alignments is likely to be required to extract the lensing signal to sufficient accuracy. We present a new model based on the placement of galaxies into dark matter haloes. The central galaxy ellipticity follows the large-scale potential and, in the simplest case, the satellite galaxies point at the halo centre. The two-halo term is then dominated by the linear-alignment model and the one-halo term provides a motivated extension of intrinsic alignment models to small scales. We provide fitting formulae for the spatial projected source power spectra for both intrinsic-intrinsic (II) and gravitational-intrinsic (GI) correlations. We illustrate the potential impact of ignoring intrinsic alignments on cosmological parameter constraints from non-tomographic surveys, finding that σ 8 could be underestimated by up to the size of the current 1σ error bar from cosmic shear if very small scales are included in the analysis. Finally, we highlight areas of interest for numerical simulations of dark matter clustering and galaxy formation that can further constrain the intrinsic alignment signal.

Subfields: Astronomy and Astrophysics, Instrumentation

View Paper: https://www.semanticscholar.org/paper/b22f626c784b03c3b38fa7a25dbb96a23fd60d5d

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Citations in the corpus

Mapping stellar content to dark matter haloes using galaxy clustering and galaxy–galaxy lensing in the SDSS DR7 (2015, unknown): “…of these theoretical uncertainties include halo modelling of the galaxy-shear crosscorrelation (galaxy-galaxy lensing) in combination with galaxy clustering and cosmic shear, instead of using cosmic shear alone (e.g., Schneider & Bridle 2010; Semboloni et al. 2011; 2013; Zentner et al. 2013).”
The Intrinsic Alignment of Galaxies and its Impact on Weak Gravitational Lensing in an Era of Precision Cosmology (2014, methodology): “Best-fit values for qij are given in Schneider and Bridle (2010).”
Intrinsic alignments of SDSS-III BOSS LOWZ sample galaxies (2014, methodology): “To extend this model of intrinsic alignments into scales comparable to or smaller than the sizes of dark matter halos, Schneider & Bridle (2010) proposed the halo model for intrinsic alignments.”
Origins of weak lensing systematics, and requirements on future instrumentation (or knowledge of instrumentation) (2012, background): “…= 〈γ〉 so long as the intrinsic galaxy ellipticities are random and hence 〈εint〉 = 0 (but see Crittenden et al. 2001; Catelan et al. 2001; Natarajan et al. 2001; Joachimi & Schneider 2008; Schneider & Bridle 2010; Kirk et al. 2012, for instances of ‘intrinsic alignments’ when this does not hold).”
Masses of Galaxy Clusters from Gravitational Lensing (2013, background): “Under the assumption that the original position angles of the galaxies are distributed randomly (see, however, e.g., Hirata & Seljak 2004; Mandelbaum et al. 2006; Schneider & Bridle 2010; Joachimi et al. 2011), the lensing shear can be inferred by averaging over an ensemble of sources.”
Spin alignments within the cosmic web: a theory of constrained tidal torques near filaments (2015, background): “In parallel, much analytical (e.g. Catelan et al. 2001; Hirata & Seljak 2004), numerical (e.g. Heavens et al. 2000; Croft & Metzler 2000; Schneider & Bridle 2010; Schneider et al. 2012; Joachimi et al. 2013b; Codis et al. 2015; Tenneti et al. 2015) and observational (e.g. Brown et al. 2002; Lee &…”
Simultaneous measurement of cosmology and intrinsic alignments using joint cosmic shear and galaxy number density correlations (2009, methodology): “Currently, the level of models is crude, and partly only motivated phenomenologically (see e.g. Schneider & Bridle 2010 for recent progress).”
The WiggleZ Dark Energy Survey: Direct constraints on blue galaxy intrinsic alignments at intermediate redshifts (2009, result): “A physically motivated model for smaller scales based on the halo model presented by Schneider & Bridle (2010) gives qualitatively similar results to the NLA.”
Galaxy Alignments: Observations and Impact on Cosmology (2015, methodology): “They found an allowed deviation significantly lower than the fiducial model assumed in Schneider & Bridle (2010).”
Constraints on intrinsic alignment contamination of weak lensing surveys using the MegaZ-LRG sample (2010, methodology): “However, as for II correlations, modelling attempts (Hui & Zhang 2002; Hirata & Seljak 2004; Heymans et al. 2006; Schneider & Bridle 2010) do not currently yield robust predictions.”