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

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 K&#xf6;hlinger</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">Bj&#xf6;rn Malte Sch&#xe4;fer</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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