Observing relativistic features in large-scale structure surveys — II: Doppler magnification in an ensemble of relativistic simulations. (arXiv:2011.12936v1 [astro-ph.CO])

<a href="http://arxiv.org/find/astro-ph/1/au:+Coates_L/0/1/0/all/0/1">Louis Coates</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Adamek_J/0/1/0/all/0/1">Julian Adamek</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Bull_P/0/1/0/all/0/1">Philip Bull</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Guandalin_C/0/1/0/all/0/1">Caroline Guandalin</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Clarkson_C/0/1/0/all/0/1">Chris Clarkson</a>

The standard cosmological model is inherently relativistic, and yet a wide

range of cosmological observations can be predicted accurately from essentially

Newtonian theory. This is not the case on `ultra-large’ distance scales, around

the cosmic horizon size, however, where relativistic effects can no longer be

neglected. In this paper, we present a novel suite of 53 fully relativistic

simulations generated using the gevolution code, each covering the full sky out

to $z approx$ 0.85, and approximately 1930 square degrees out to $z approx$

3.55. These include a relativistic treatment of massive neutrinos, as well as

the gravitational potential that can be used to exactly calculate observables

on the past light cone. The simulations are divided into two sets, the first

being a set of 39 simulations of the same fiducial cosmology (based on the

Euclid Flagship 2 cosmology) with different realisations of the initial

conditions, and the second which fixes the initial conditions, but varies each

of seven cosmological parameters in turn. Taken together, these simulations

allow us to perform statistical studies and calculate derivatives of any

relativistic observable with respect to cosmological parameters. As an example

application, we compute the cross-correlation between the Doppler magnification

term in the convergence, $kappa_v$, and the CDM+baryon density contrast,

$delta_{rm cb}$, which arises only in a (special) relativistic treatment. We

are able to accurately recover this term as predicted by relativistic

perturbation theory, and study its sample variance and derivatives with respect

to cosmological parameters.

The standard cosmological model is inherently relativistic, and yet a wide

range of cosmological observations can be predicted accurately from essentially

Newtonian theory. This is not the case on `ultra-large’ distance scales, around

the cosmic horizon size, however, where relativistic effects can no longer be

neglected. In this paper, we present a novel suite of 53 fully relativistic

simulations generated using the gevolution code, each covering the full sky out

to $z approx$ 0.85, and approximately 1930 square degrees out to $z approx$

3.55. These include a relativistic treatment of massive neutrinos, as well as

the gravitational potential that can be used to exactly calculate observables

on the past light cone. The simulations are divided into two sets, the first

being a set of 39 simulations of the same fiducial cosmology (based on the

Euclid Flagship 2 cosmology) with different realisations of the initial

conditions, and the second which fixes the initial conditions, but varies each

of seven cosmological parameters in turn. Taken together, these simulations

allow us to perform statistical studies and calculate derivatives of any

relativistic observable with respect to cosmological parameters. As an example

application, we compute the cross-correlation between the Doppler magnification

term in the convergence, $kappa_v$, and the CDM+baryon density contrast,

$delta_{rm cb}$, which arises only in a (special) relativistic treatment. We

are able to accurately recover this term as predicted by relativistic

perturbation theory, and study its sample variance and derivatives with respect

to cosmological parameters.

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