KiDS+GAMA: Constraints on Horndeski gravity from combined large-scale structure probes. (arXiv:1901.03686v1 [astro-ph.CO])

<a href="http://arxiv.org/find/astro-ph/1/au:+Mancini_A/0/1/0/all/0/1">Alessio Spurio Mancini</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Kohlinger_F/0/1/0/all/0/1">Fabian Köhlinger</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Joachimi_B/0/1/0/all/0/1">Benjamin Joachimi</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Pettorino_V/0/1/0/all/0/1">Valeria Pettorino</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Schafer_B/0/1/0/all/0/1">Björn Malte Schäfer</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Reischke_R/0/1/0/all/0/1">Robert Reischke</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Brieden_S/0/1/0/all/0/1">Samuel Brieden</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Archidiacono_M/0/1/0/all/0/1">Maria Archidiacono</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Lesgourgues_J/0/1/0/all/0/1">Julien Lesgourgues</a>

We present constraints on Horndeski gravity from a combined analysis of

cosmic shear, galaxy-galaxy lensing and galaxy clustering from

$450,mathrm{deg}^2$ of the Kilo-Degree Survey (KiDS) and the Galaxy And Mass

Assembly (GAMA) survey, including all cross-correlations. The Horndeski class

of dark energy/modified gravity models includes the majority of universally

coupled extensions to $Lambda$CDM with one scalar degree of freedom in

addition to the metric. We study the functions of time that fully describe the

evolution of linear perturbations in Horndeski gravity, and set constraints on

parameters that describe their time evolution. Our results are compatible

throughout with a $Lambda$CDM model. Assuming proportionality of the Horndeski

functions $alpha_B$ and $alpha_M$ (describing the braiding of the scalar

field with the metric and the Planck mass run rate, respectively) to the dark

energy density fraction $Omega_{mathrm{DE}}(a) = 1 – Omega_{mathrm{m}}(a)$,

we find for the proportionality coefficients $hat{alpha}_B =

0.20_{-0.33}^{+0.20} ,$ and $, hat{alpha}_M = 0.25_{-0.29}^{+0.19}$. Our

value of $S_8 equiv sigma_8 sqrt{Omega_{mathrm{m}}/0.3}$ is in better

agreement with the $Planck$ estimate when measured in the enlarged Horndeski

parameter space than in a pure $Lambda$CDM scenario. In our Horndeski gravity

analysis of cosmic shear alone, we report a downward shift of the $S_8$ best

fit value from the $Planck$ measurement of $Delta S_8 =

0.048_{-0.056}^{+0.059}$, compared to $Delta S_8 = 0.091_{-0.045}^{+0.046}$ in

$Lambda$CDM. In the joint three-probe analysis, we find $Delta S_8 =

0.016_{-0.046}^{+0.048}$ in Horndeski gravity and $Delta S_8 =

0.059_{-0.039}^{+0.040}$ in $Lambda$CDM. Our likelihood code for multi-probe

analysis in both $Lambda$CDM and Horndeski gravity is made publicly available.

We present constraints on Horndeski gravity from a combined analysis of

cosmic shear, galaxy-galaxy lensing and galaxy clustering from

$450,mathrm{deg}^2$ of the Kilo-Degree Survey (KiDS) and the Galaxy And Mass

Assembly (GAMA) survey, including all cross-correlations. The Horndeski class

of dark energy/modified gravity models includes the majority of universally

coupled extensions to $Lambda$CDM with one scalar degree of freedom in

addition to the metric. We study the functions of time that fully describe the

evolution of linear perturbations in Horndeski gravity, and set constraints on

parameters that describe their time evolution. Our results are compatible

throughout with a $Lambda$CDM model. Assuming proportionality of the Horndeski

functions $alpha_B$ and $alpha_M$ (describing the braiding of the scalar

field with the metric and the Planck mass run rate, respectively) to the dark

energy density fraction $Omega_{mathrm{DE}}(a) = 1 – Omega_{mathrm{m}}(a)$,

we find for the proportionality coefficients $hat{alpha}_B =

0.20_{-0.33}^{+0.20} ,$ and $, hat{alpha}_M = 0.25_{-0.29}^{+0.19}$. Our

value of $S_8 equiv sigma_8 sqrt{Omega_{mathrm{m}}/0.3}$ is in better

agreement with the $Planck$ estimate when measured in the enlarged Horndeski

parameter space than in a pure $Lambda$CDM scenario. In our Horndeski gravity

analysis of cosmic shear alone, we report a downward shift of the $S_8$ best

fit value from the $Planck$ measurement of $Delta S_8 =

0.048_{-0.056}^{+0.059}$, compared to $Delta S_8 = 0.091_{-0.045}^{+0.046}$ in

$Lambda$CDM. In the joint three-probe analysis, we find $Delta S_8 =

0.016_{-0.046}^{+0.048}$ in Horndeski gravity and $Delta S_8 =

0.059_{-0.039}^{+0.040}$ in $Lambda$CDM. Our likelihood code for multi-probe

analysis in both $Lambda$CDM and Horndeski gravity is made publicly available.

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