Intrinsic galaxy alignments from the 2SLAQ and SDSS surveys: luminosity and redshift scalings and implications for weak lensing surveys

By C. Hirata, Rachel Mandelbaum, M. Ishak, Uros Seljak, Robert Nichol, Kevin A. Pimbblet, N. Ross, D. Wake. 2007

223 citations recorded by the source corpus.

Correlations between intrinsic shear and the density field on large scales, a potentially important contaminant for cosmic shear surveys, have been robustly detected at low redshifts with bright galaxies in Sloan Digital Sky Survey (SDSS) data. Here we present a more detailed characterization of this effect, which can cause anticorrelations between gravitational lensing shear and intrinsic ellipticity (GI correlations). This measurement uses 36 278 luminous red galaxies (LRGs) from the SDSS spectroscopic sample with 0.15 3σ detections of the effect on large scales (up to 60 h−1 Mpc) for all galaxy subsamples within the SDSS LRG sample; for the 2SLAQ sample, we find a 2σ detection for a bright subsample, and no detection for a fainter subsample. Fitting formulae are provided for the scaling of the GI correlations with luminosity, transverse separation and redshift (for which the 2SLAQ sample, while small, provides crucial constraints due to its longer baseline in redshift). We estimate contamination in the measurement of σ8 for future cosmic shear surveys on the basis of the fitted dependence of GI correlations on galaxy properties. We find contamination to the power spectrum ranging from −1.5 per cent (optimistic) to −33 per cent (pessimistic) for a toy cosmic shear survey using all galaxies to a depth of R = 24 using scales l ≈ 500, though the central value of predicted contamination is −6.5 per cent. This corresponds to a bias in σ8 of Δσ8 = −0.004 (optimistic), −0.02 (central) or −0.10 (pessimistic). We provide a prescription for inclusion of this error in cosmological parameter estimation codes. The principal uncertainty is in the treatment of the L ≤ L blue galaxies, for which we have no detection of the GI signal, but which could dominate the GI contamination if their GI amplitude is near our upper limits. Characterization of the tidal alignments of these galaxies, especially at redshifts relevant for cosmic shear, should be a high priority for the cosmic shear community.

Subfields: Astronomy and Astrophysics

View Paper: https://www.semanticscholar.org/paper/91e7f7bfafee0700ea74ab20176150d3af7052e3

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Citations in the corpus

Galaxy Alignments: Observations and Impact on Cosmology (2015, methodology): “Interpretation of this data by Blazek et al. (2011) in terms of the non-linear alignment model reveal a systematically higher amplitude compared to measurements for comparable samples in Hirata et al. (2007) and Joachimi et al. (2011).”
Observational probes of cosmic acceleration (2012, methodology): “We learned that large-scale intrinsic galaxy alignments are strongest for luminous red galaxies (Hirata et al., 2007; Mandelbaum et al., 2011), and that the linear alignment model, once considered a crude analytical tool (Catelan et al., 2001), is in fact an excellent description of the…”
Galaxy Alignments: An Overview (2015, methodology): “The red sample results use the sample from Hirata et al. (2007), but were re-measured by Joachimi et al. (2011) using a different colour cut that is more consistent with ones used by later works.”
Evidence of the accelerated expansion of the Universe from weak lensing tomography with COSMOS (2009, background): “In addition, we exclude luminous red galaxies, which were found to carry the strongest intrinsic alignment with the density field of their large-scale structure environment causing the s ear (Hirata et al. 2007).”
Spin alignments within the cosmic web: a theory of constrained tidal torques near filaments (2015, background): “…Brown et al. 2002; Lee & Pen 2002; Bernstein & Norberg 2002; Heymans et al. 2004; Hirata et al. 2004; Hirata & Seljak 2004; Mandelbaum et al. 2006; Hirata et al. 2007; Mandelbaum et al. 2011; Joachimi et al. 2011, 2013a) efforts have been invested to control the level of in- © 0000 The Authors ar…”
Cosmological constraints from the 100-deg2 weak-lensing survey (2007, methodology): “…however is the level of systematic error that arises from shear–ellipticity correlations (Hirata & Seljak 2004; Mandelbaum et al. 2006; Heymans et al. 2006b; Hirata et al. 2007) which could reduce the amplitude of the measured shear correlation function by ∼10 per cent (Heymans et al. 2006b).”
Practical Weak-lensing Shear Measurement with Metacalibration (2017, background): “Remarks on Intrinsic Alignments In the above we assumed that P (eα, eβ) is separable at zero shear, but this assumption breaks down for physically associated galaxies (e.g. Hirata et al. 2007), an affect known as “intrinsic alignments” (IA; for a recent review, see Troxel & Ishak 2015).”
KiDS+GAMA : cosmology constraints from a joint analysis of cosmic shear, galaxy-galaxy lensing, and angular clustering (2017, background): “…although intrinsic alignments have been detected for luminous red galaxies (e.g. Joachimi et al. 2011; Singh, Mandelbaum & More 2015), the constraints for less luminous red galaxies and blue galaxies are consistent with zero (Mandelbaum et al. 2006; Hirata et al. 2007; Mandelbaum et al. 2011).”
Gravitational lensing (2010, background): “They quantified this systematic effect [191, 298] and showed that it can substantially reduce the measured shear signal, leading to a likely underestimate of the σ8 parameter by several per cents.”
Cosmological parameter constraints from galaxy-galaxy lensing and galaxy clustering with the SDSS DR7 (2012, background): “…scales used for the cosmological constraints in this paper. c© 0000 RAS, MNRAS 000, 000–000 extent (Hirata & Seljak 2004); this alignment has been observed (e.g., Hirata et al. 2007) but primarily for bright red galaxies, rather than the faint ones that we use as sources in our lensing analysis.”
The WiggleZ Dark Energy Survey: Direct constraints on blue galaxy intrinsic alignments at intermediate redshifts (2009, methodology): “Next, Hirata et al. (2007) showed results for the Main sample split into both colour and luminosity bins, in addition to new results from the SDSS LRG sample (red galaxies with z ∼ 0.3) and from the 2SLAQ redshift survey using shape measurements from SDSS.”
The Intrinsic Alignment of Galaxies and its Impact on Weak Gravitational Lensing in an Era of Precision Cosmology (2014, methodology): “The best-fit values of A and θ0 are given in Table 1 of Semboloni et al. (2008) for several choices of lens distribution and source redshifts.”
Intrinsic alignments of SDSS-III BOSS LOWZ sample galaxies (2014, methodology): “Hirata et al. (2007) and Joachimi et al. (2011) also observed luminosity dependence of intrinsic alignments, with more luminous objects having stronger alignments.”
CFHTLenS tomographic weak lensing cosmological parameter constraints: Mitigating the impact of intrinsic galaxy alignments (2013, methodology): “As noted in Hirata et al. (2007), the Catelan et al. (2001) model of linear galaxy alignment has no sound grounding in theory, in contrast to the analytical models of angular momentum correlations, and hence galaxy alignment, from tidal torque theory (see the review by Schäfer 2009, and references…”
Core Cosmology Library: Precision Cosmological Predictions for LSST (2018, unknown): “CCL supports the so-called “non-linear alignment model” (NLA), in which the intrinsic galaxy inertia tensor is proportional the local tidal tensor (Catelan et al. 2001; Hirata & Seljak 2004; Hirata et al. 2007): ∆IA` (k) = √ (`+ 2)!”