Spin-induced Galaxy Alignments and Their Implications for Weak-Lensing Measurements

By Robert G. Crittenden, P. Natarajan, Ue-Li Pen, Tom Theuns. 2000

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Large-scale correlations in the orientations of galaxies can result from alignments in their angular momentum vectors. These alignments arise from the tidal torques exerted on neighboring protogalaxies by the smoothly varying shear field. We compute the predicted amplitude of such ellipticity correlations using the Zeldovich approximation for a realistic distribution of galaxy shapes. Weak gravitational lensing can also induce ellipticity correlations, since the images of neighboring galaxies will be distorted coherently. On comparing these two effects that induce shape correlations, we find that for current weak-lensing surveys with a median redshift of zm = 1, the intrinsic signal is of the order of 1%-10% of the measured signal. However, for shallower surveys with zm ≤ 0.3, the intrinsic correlations dominate over the lensing signal. The distortions induced by lensing are curl-free, whereas those resulting from intrinsic alignments are not. This difference can be used to disentangle these two sources of ellipticity correlations.

Subfields: Astronomy and Astrophysics

View Paper: https://www.semanticscholar.org/paper/7ad147d8693a289c5c7d08707b0296b7ee3f0a0a

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Citations in the corpus

Simultaneous measurement of cosmology and intrinsic alignments using joint cosmic shear and galaxy number density correlations (2009, background): “…Energy Mission,http://jdem.gdfc.nasa.gov 5 http://sci.esa.int/science-e/www/area/ index.cfm?fareaid=102 2000; Lee & Pen 2000; Catelan et al. 2001; Crittenden et al. 2001; Jing 2002; Mackey et al. 2002; Hirata & Seljak 2004; Bridle & Abdalla 2007; Schneider & Bridle 2010), as well as the…”
Detection of large-scale intrinsic ellipticity—density correlation from the Sloan Digital Sky Survey and implications for weak lensing surveys (2005, background): “…the theoretical predictions vary by more than an order of magnitude for II (Croft & Metzler 2000; Heavens et al. 2000; Lee & Pen 2000, 2001; Catelan et al. 2001; Crittenden et al. 2001; Jing 2002), so there is a clear role for observations in distinguishing which of these models is correct.”
Weak Gravitational Lensing by Large-Scale Structure (2003, methodology): “Another approach is to search for the B-type correlation signal produced by intrinsic correlations (Crittenden et al. 2001b).”
Results of the GREAT08 Challenge?: an image analysis competition for cosmological lensing: Results o (2009, result): “This distribution was loosely motivated by results from the APM survey (Crittenden et al. 2001).”
Weak-Lensing Results from the 75 Square Degree Cerro Tololo Inter-American Observatory Survey (2003, background): “Crittenden et al. (2001) calculate the correlation function that may exist due to spin correlations between galaxies.”
COSMOS: Three-dimensional Weak Lensing and the Growth of Structure (2007, background): “2D E-B Decomposition The correlation functions can also be recast in terms of nonlocal E (gradient) and B (curl) patterns in the shear field (Crittenden et al. 2001; Pen et al. 2002).”
Galaxy Alignments: An Overview (2015, background): “Assuming that the ellipticity of a galaxy is given by the projection of a circular disc which is orthogonal to the angular momentum direction of the galaxy, the intrinsic shear can be computed as (Catelan et al. 2001; Crittenden et al. 2001)”
Internal and External Alignment of the Shapes and Angular Momenta of ΛCDM Halos (2004, methodology): “Linear tidal torque theory (Doroshkevich 1970; White 1984) can be used to predict the directions of the angular momentum vectors and their correlations with the surrounding structure (Pen et al. 2000; Lee & Pen 2000, 2001; Crittenden et al. 2001; Porciani et al. 2002a,b).”
The Angular Momentum of Gas in Protogalaxies. I. Implications for the Formation of Disk Galaxies (2002, methodology): “In the past, both tidal torque theory (Crittenden et al. 2001; Heavens, Refegier, & Heymans 2000; Natarajan et al. 2001) and pureN-body simulations (Croft & Metzler 2000) have been used to calculate the possibility of intrinsic alignments of galaxy shapes, which may be responsible for part of the…”
Testing tidal-torque theory – II. Alignment of inertia and shear and the characteristics of protohaloes (2001, background): “Other applications have made the assumption that the present-day halo angular momentum correlates with the shear tensor of the initial conditions (LP00; Pen, Lee & Seljak 2000; Crittenden et al. 2001).”
Measurement of intrinsic alignments in galaxy ellipticities (2000, methodology): “Over the last year, this problem has been addressed by a number of groups using a combination of numerical (Heavens, Refregier & Heymans 2000, Croft & Metzler 2001) and analytic methods (Catelan, Kamionkowski & Blandford 2001, Crittenden et al 2001).”
Potential sources of contamination to weak lensing measurements: constraints from N-body simulations (2006, background): “(2006)), analytically (Catelan et al. 2001; Crittenden et al. 2001; Lee & Pen 2001; Porciani et al. 2002; Mackey et al. 2002) and through numerical simulations (Heavens et al. (2000), hereafter HRH, Croft & Metzler (2000); Jing (2002), H04), it is currently thought that this intrinsic alignment…”
Connecting the cosmic web to the spin of dark haloes: implications for galaxy formation (2012, background): “…tensor and the local gravitational tidal tensor at the time of maximum expansion; this is the basis of the so-called Tidal Torque Theory (TTT hereafter, Hoyle 1949; Peebles 1969; Doroshkevich 1970; White 1984; Catelan & Theuns 1996; Crittenden et al. 2001; Schäfer 2009, for a recent review).”