Higher order relativistic galaxy number counts: dominating terms

Nielsen, Jeppe Trøst; Durrer, Ruth

doi:10.1088/1475-7516/2017/03/010

Cited by 29 publications

(36 citation statements)

References 46 publications

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“…where Φ A = (Φ + Ψ), Φ and Ψ are the gravitational potential and scalar curvature perturbations respectively. χ is the comoving distance to the source, it is related to the affine parameter(or conformal time) on the conformal background spacetime, (16) is in agreement with the argument in [22] on how to correctly implement the post-Born corrections. Equation (15) is related to the gravitational lensing bending angle at linear order, while equation (16) is the corresponding expression at second order.…”

Section: Perturbation Of Hi Brightness Temperaturesupporting

confidence: 77%

“…In this section, we compute the power spectrum of the HI brightness temperature using the results derived in section II in the plane-parallel limit. The HI density contrast that appears in equations (21), (22) and (23) is given in conformal Newtonian gauge, while the concept of bias only makes sense in the frame where the HI brightness temperature is at rest, i.e comoving synchronous gauge. Thus, we, first of all, transform δ HI into comoving synchronous gauge and at linear order, we find…”

Section: Power Spectrum Of the Hi Brightness Temperature In Redsmentioning

confidence: 99%

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Imprint of non-linear effects on HI intensity mapping on large scales

Umeh

2017

J. Cosmol. Astropart. Phys.

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Intensity mapping of the HI brightness temperature provides a unique way of tracing largescale structures of the Universe up to the largest possible scales. This is achieved by using a low angular resolution radio telescopes to detect emission line from cosmic neutral Hydrogen in the post-reionization Universe. We use general relativistic perturbation theory techniques to derive for the first time the full expression for the HI brightness temperature up to third order in perturbation theory without making any plane-parallel approximation. We use this result and the renormalization prescription for biased tracers to study the impact of nonlinear effects on the power spectrum of HI brightness temperature both in real and redshift space. We show how mode coupling at nonlinear order due to nonlinear bias parameters and redshift space distortion terms modulate the power spectrum on large scales. The large scale modulation may be understood to be due to the effective bias parameter and effective shot noise.

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Section: Perturbation Of Hi Brightness Temperaturesupporting

confidence: 77%

Section: Power Spectrum Of the Hi Brightness Temperature In Redsmentioning

confidence: 99%

Imprint of non-linear effects on HI intensity mapping on large scales

Umeh

2017

J. Cosmol. Astropart. Phys.

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“…The second order relativistic calculation of the observed galaxy number counts has been developed by three independent groups [24][25][26] and recently compared partially in [47]. In particular, in [26] the second-order galaxy number counts are calculated using a geometrical approach based on the so-called geodesic light-cone coordinates [48], and it is valid for any metric theory with perturbations around FLRW metric.…”

Section: Bispectrum From Second-order Perturbation Theorymentioning

confidence: 99%

Non-Gaussianities due to relativistic corrections to the observed galaxy bispectrum

Dio

Perrier

Durrer

et al. 2017

J. Cosmol. Astropart. Phys.

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Abstract. High-precision constraints on primordial non-Gaussianity (PNG) will significantly improve our understanding of the physics of the early universe. Among all the subtleties in using large scale structure observables to constrain PNG, accounting for relativistic corrections to the clustering statistics is particularly important for the upcoming galaxy surveys covering progressively larger fraction of the sky. We focus on relativistic projection effects due to the fact that we observe the galaxies through the light that reaches the telescope on perturbed geodesics. These projection effects can give rise to an effective f NL that can be misinterpreted as the primordial non-Gaussianity signal and hence is a systematic to be carefully computed and accounted for in modelling of the bispectrum. We develop the technique to properly account for relativistic effects in terms of purely observable quantities, namely angles and redshifts. We give some examples by applying this approach to a subset of the contributions to the tree-level bispectrum of the observed galaxy number counts calculated within perturbation theory and estimate the corresponding non-Gaussianity parameter, f NL , for the local, equilateral and orthogonal shapes. For the local shape, we also compute the local non-Gaussianity resulting from terms obtained using the consistency relation for observed number counts. Our goal here is not to give a precise estimate of f NL for each shape but rather we aim to provide a scheme to compute the non-Gaussian contamination due to relativistic projection effects. For the terms considered in this work, we obtain contamination of f loc NL ∼ O(1).

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“…The dominating terms of the full second order calculations have been reviewed in Ref. [19]. More recently in Ref.…”

Section: Introductionmentioning

confidence: 99%

Galaxy number counts at second order: an independent approach

Fuentes,

Hidalgo,

Malik

2019

Preprint

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Next generation surveys will be capable of determining cosmological parameters beyond percent level. To match this precision, theoretical descriptions should look beyond the linear perturbations to approximate the observables in large scale structure. A quantity of interest is the Number density of galaxies detected by our instruments. This has been focus of interest recently, and several efforts have been made to explain relativistic effects theoretically, thereby testing the full theory. However, the results at nonlinear level from previous works are in disagreement. We present a new and independent approach to computing the relativistic galaxy number counts to second order in cosmological perturbation theory. We derive analytical expressions for the full second order relativistic observed redshift, for the angular diameter distance and for the volume spanned by a survey. Finally, we compare our results with previous works which compute the general distance-redshift relation, finding that our result is in agreement at linear order.

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Higher order relativistic galaxy number counts: dominating terms

Cited by 29 publications

References 46 publications

Imprint of non-linear effects on HI intensity mapping on large scales

Imprint of non-linear effects on HI intensity mapping on large scales

Non-Gaussianities due to relativistic corrections to the observed galaxy bispectrum

Galaxy number counts at second order: an independent approach

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