Cosmic rulers

Schmidt, Fabian; Jeong, Donghui

doi:10.1103/physrevd.86.083527

Cited by 134 publications

(377 citation statements)

References 35 publications

(68 reference statements)

Supporting

Mentioning

357

Contrasting

Order By: Relevance

“…In order to relate this bispectrum to observations from large-scale structure surveys, projection effects due to photon propagation through a perturbed background need to be included. While the ruler perturbations of [50] in principle provide all the necessary projection effects, we leave the detailed calculation of these to future work. the expected term satisfying the conformal Newtonian gauge condition h ij = δ ij h 00 in the absence of anisotropic stress.…”

Section: Discussionmentioning

confidence: 99%

On separate universes

Dai

Pajer

Schmidt

2015

J. Cosmol. Astropart. Phys.

Self Cite

188

View full text Add to dashboard Cite

Abstract. The separate universe conjecture states that in General Relativity a density perturbation behaves locally (i.e. on scales much smaller than the wavelength of the mode) as a separate universe with different background density and curvature. We prove this conjecture for a spherical compensated tophat density perturbation of arbitrary amplitude and radius in ΛCDM. We then use Conformal Fermi Coordinates to generalize this result to scalar perturbations of arbitrary configuration and scale in a general cosmology with a mixture of fluids, but to linear order in perturbations. In this case, the separate universe conjecture holds for the isotropic part of the perturbations. The anisotropic part on the other hand is exactly captured by a tidal field in the Newtonian form. We show that the separate universe picture is restricted to scales larger than the sound horizons of all fluid components. We then derive an expression for the locally measured matter bispectrum induced by a long-wavelength mode of arbitrary wavelength, a new result which in standard perturbation theory is equivalent to a relativistic second-order calculation. We show that nonlinear gravitational dynamics does not generate observable contributions that scale like local-type non-Gaussianity f loc NL , and hence does not contribute to a scale-dependent galaxy bias ∆b ∝ k −2 on large scales; rather, the locally measurable long-short mode coupling assumes a form essentially identical to subhorizon perturbation theory results, once the long-mode density perturbation is replaced by the synchronous-comoving gauge density perturbation. Apparent f loc NL -type contributions arise through projection effects on photon propagation, which depend on the specific large-scale structure tracer and observable considered, and are in principle distinguishable from the local mode coupling induced by gravity. We conclude that any observation of f loc NL beyond these projection effects signals a departure from standard single-clock inflation.

show abstract

Section: Discussionmentioning

confidence: 99%

On separate universes

Dai

Pajer

Schmidt

2015

J. Cosmol. Astropart. Phys.

Self Cite

188

View full text Add to dashboard Cite

show abstract

“…Firstly, it is known that it does not hold for tensor perturbations, this is the origin of the "metric shear" term (see e.g. Schmidt & Jeong 2012). This is not an issue in this work as we do not deal with tensor perturbations.…”

Section: Rotation To B-mode Correspondencementioning

confidence: 99%

Estimating the weak-lensing rotation signal in radio cosmic shear surveys

Thomas

Whittaker

Camera

et al. 2017

Monthly Notices of the Royal Astronomical Society

View full text Add to dashboard Cite

Weak lensing has become an increasingly important tool in cosmology and the use of galaxy shapes to measure cosmic shear has become routine. The weak-lensing distortion tensor contains two other effects in addition to the two components of shear: the convergence and rotation. The rotation mode is not measurable using the standard cosmic shear estimators based on galaxy shapes, as there is no information on the original shapes of the images before they were lensed. Due to this, no estimator has been proposed for the rotation mode in cosmological weak-lensing surveys, and the rotation mode has never been constrained. Here, we derive an estimator for this quantity, which is based on the use of radio polarisation measurements of the intrinsic position angles of galaxies. The rotation mode can be sourced by physics beyond ΛCDM, and also offers the chance to perform consistency checks of ΛCDM and of weak-lensing surveys themselves. We present simulations of this estimator and show that, for the pedagogical example of cosmic string spectra, this estimator could detect a signal that is consistent with the constraints from Planck. We examine the connection between the rotation mode and the shear B-modes and thus how this estimator could help control systematics in future radio weak-lensing surveys.

show abstract

“…We set up a map between redshift space and real space (see Fig. 1), generalizing the cosmic rulers approach of [6,15] from first to second order. The observed galaxy has conformal coordinates x µ = (η,x) = (η 0 −χ,χ n i ) in redshift space.…”

Section: Figmentioning

confidence: 99%

Observed galaxy number counts on the lightcone up to second order: I. Main result

Bertacca

Maartens

Clarkson

2014

J. Cosmol. Astropart. Phys.

154

View full text Add to dashboard Cite

We present the galaxy number overdensity up to second order in redshift space on cosmological scales for a concordance model. The result contains all general relativistic effects up to second order that arise from observing on the past light cone, including all redshift effects, lensing distortions from convergence and shear, and contributions from velocities, Sachs-Wolfe, integrated SW and time-delay terms. This result will be important for accurate calculation of the bias on estimates of non-Gaussianity and on precision parameter estimates, introduced by nonlinear projection effects.

show abstract

Cosmic rulers

Cited by 134 publications

References 35 publications

On separate universes

On separate universes

Estimating the weak-lensing rotation signal in radio cosmic shear surveys

Observed galaxy number counts on the lightcone up to second order: I. Main result

Contact Info

Product

Resources

About