Intrinsic ellipticity correlations of galaxies: models, likelihoods and interplay with weak lensing

Capranico, Federica; Merkel, Philipp M.; Schäfer, Björn Malte

doi:10.1093/mnras/stt1269

Cited by 15 publications

(19 citation statements)

References 89 publications

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“…Crittenden et al 2001Crittenden et al , 2002Capranico et al 2013;. Following the work of Crittenden et al (2001), Capranico et al (2013) computed angular ellipticity power spectra and compared these with weak lensing shear power spectra. The intrinsic E-mode (II) spectra resulting from the quadratic alignments was found to be an order of magnitude less than the weak lensing power spectra for lensing surveys reaching unit redshift, while the B-mode spectra would be an important test of systematics.…”

Section: Quadratic Alignment Model For Spiral Galaxiesmentioning

confidence: 99%

Galaxy Alignments: Theory, Modelling & Simulations

et al. 2015

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The shapes of galaxies are not randomly oriented on the sky. During the galaxy formation and evolution process, environment has a strong influence, as tidal gravitational fields in the large-scale structure tend to align nearby galaxies. Additionally, events such as galaxy mergers affect the relative alignments of both the shapes and angular momenta of galaxies throughout their history. These "intrinsic galaxy alignments" are known to exist, but are still poorly understood. This review will offer a pedagogical introduction to the current theories that describe intrinsic galaxy alignments, including the apparent difference in intrinsic alignment between early-and late-type galaxies and the latest efforts to model them analytically. It will then describe the ongoing efforts to simulate intrinsic alignments using both N-body and hydrodynamic simulations. Due to the relative youth of this field, there is still much to be done to understand intrinsic galaxy alignments and this review summarises the current state of the field, providing a solid basis for future work.

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Section: Quadratic Alignment Model For Spiral Galaxiesmentioning

confidence: 99%

Galaxy Alignments: Theory, Modelling & Simulations

et al. 2015

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“…Kirk et al (2012) found the bias in the equation of state parameter w 0 to be as large as 8-20 σ, but estimates vary depending on the modelling of the spurious contribution to the shear spectrum (cf. Bridle & King 2007;Capranico et al 2013), implying that the impact on cosmological constraints is still far from clear. For three-dimensional cosmic shear, Merkel & Schäfer (2013b) presented auto-and crosscovariances of intrinsic and lensing-induced ellipticities.…”

Section: Discussionmentioning

confidence: 99%

The cross-correlation between 3D cosmic shear and the integrated Sachs–Wolfe effect

Zieser

Merkel

2016

Mon. Not. R. Astron. Soc.

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We present the first calculation of the cross-correlation between three-dimensional cosmic shear and the integrated Sachs-Wolfe (iSW) effect. Both signals are combined in a single formalism, which permits the computation of the full covariance matrix. In order to avoid the uncertainties presented by the non-linear evolution of the matter power spectrum and intrinsic alignments of galaxies, our analysis is restricted to large scales, i.e. multipoles below = 1000. We demonstrate in a Fisher analysis that this reduction compared to other studies of three-dimensional weak lensing extending to smaller scales is compensated by the information that is gained if the additional iSW signal and in particular its cross-correlation with lensing data are considered. Given the observational standards of upcoming weak lensing surveys like Euclid, marginal errors on cosmological parameters decrease by ten per cent compared to a cosmic shear experiment if both types of information are combined without a CMB prior. Once the constraining power of CMB data is added, the improvement becomes marginal.

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“…It is notable that the shapes of elliptical galaxies and lensing measure tidal field components perpendicular to the line of sight and are proportional to the magnitude of the tidal shears, but that in contrast spiral galaxies reflect with their shapes the tidal field orientation including line of sight-components. For details on the derivation of angular shape correlation functions and E/B-mode ellipticity spectra we refer to Capranico et al (2013), Schaefer & Merkel (2015) and Tugendhat & Schaefer (2018). Contributions to the ellipticity correlations by weak gravitational lensing C γ i j ( ) (grey bands, shown separately from linear structure formation in light grey and nonlinear structure formation in dark grey), C e,GI i j ( ) (green lines), C s,II i j ( ) (blue lines) and C e,II i j ( ) (red lines).…”

Section: Shape Correlations In a Weak Lensing Surveymentioning

confidence: 99%

Statistical separation of weak gravitational lensing and intrinsic ellipticities based on galaxy colour information

Reischke

Schäfer

2020

Monthly Notices of the Royal Astronomical Society

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Intrinsic alignments of galaxies are recognised as one of the most important systematic in weak lensing surveys on small angular scales. In this paper we investigate ellipticity correlation functions that are measured separately on elliptical and spiral galaxies, for which we assume the generic alignment mechanisms based on tidal shearing and tidal torquing, respectively. Including morphological information allows to find linear combinations of measured ellipticity correlation functions which suppress the gravitational lensing signal completely or which show a strongly boosted gravitational lensing signal relative to intrinsic alignments. Specifically, we find that (i) intrinsic alignment spectra can be measured in a model-independent way at a significance of Σ 60 with a wide-angle tomographic survey such as Euclid's, (ii) intrinsic alignment model parameters can be determined at percent-level precision, (iii) this measurement is not impeded by misclassifying galaxies and assuming a wrong alignment model, (iv) parameter estimation from a cleaned weak lensing spectrum is possible with almost no bias and (v) the misclassification would not strongly impact parameter estimation from the boosted weak lensing spectrum.

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Intrinsic ellipticity correlations of galaxies: models, likelihoods and interplay with weak lensing

Cited by 15 publications

References 89 publications

Galaxy Alignments: Theory, Modelling & Simulations

Galaxy Alignments: Theory, Modelling & Simulations

The cross-correlation between 3D cosmic shear and the integrated Sachs–Wolfe effect

Statistical separation of weak gravitational lensing and intrinsic ellipticities based on galaxy colour information

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