Degeneracies between modified gravity and baryonic physics

Ellewsen, Thor Andreas Seiff; Falck, Bridget; Mota, David F.

doi:10.1051/0004-6361/201731938

Cited by 4 publications

(3 citation statements)

References 56 publications

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“…Overall, kinematic information is an excellent observable to detect fifth force effects irrespective of the unknown neutrino mass. Using kinematic information could also be potentially useful in order to break other degeneracies with (screened) modified gravity theories such as baryonic feedback processes stemming, e.g., from AGNs which also reduce clustering (Arnold et al 2014;Ellewsen et al 2018).…”

Section: Discussionmentioning

confidence: 99%

Breaking cosmic degeneracies: Disentangling neutrinos and modified gravity with kinematic information

Hagstotz

Grönke

Mota

et al. 2019

A&A

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Searches for modified gravity in the large-scale structure try to detect the enhanced amplitude of density fluctuations caused by the fifth force present in many of these theories. Neutrinos, on the other hand, suppress structure growth below their free-streaming length. Both effects take place on comparable scales, and uncertainty in the neutrino mass leads to a degeneracy with modified gravity parameters for probes that are measuring the amplitude of the matter power spectrum. We explore the possibility to break the degeneracy between modified gravity and neutrino effects in the growth of structures by considering kinematic information related to either the growth rate on large scales or the virial velocities inside of collapsed structures. In order to study the degeneracy up to fully non-linear scales, we employ a suite of N-body simulations including both f (R) modified gravity and massive neutrinos. Our results indicate that velocity information provides an excellent tool to distinguish massive neutrinos from modified gravity. Models with different values of neutrino masses and modified gravity parameters possessing a comparable matter power spectrum at a given time have different growth rates. This leaves imprints in the velocity divergence, which is therefore better suited than the amplitude of density fluctuations to tell the models apart. In such models with a power spectrum comparable to ΛCDM today, the growth rate is strictly enhanced. We also find the velocity dispersion of virialised clusters to be well suited to constrain deviations from general relativity without being affected by the uncertainty in the sum of neutrino masses.

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Section: Discussionmentioning

confidence: 99%

Breaking cosmic degeneracies: Disentangling neutrinos and modified gravity with kinematic information

Hagstotz

Grönke

Mota

et al. 2019

A&A

Self Cite

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“…However, there has been little work on hydrodynamical simulations of non-standard gravity models (e.g. Arnold, Puchwein & Springel 2014Hammami et al 2015;Arnold, Springel & Puchwein 2016;He & Li 2016;Ellewsen, Falck & Mota 2018; Arnold, Leo & Li 2019). Exploring the effect of modified gravity on galactic scales in a cosmological context hence remains an important open topic that requires more quantitative work.…”

Section: Introductionmentioning

confidence: 99%

Galaxy formation in the brane world I: overview and first results

Hernández‐Aguayo

Arnold

et al. 2021

Monthly Notices of the Royal Astronomical Society

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We carry out “full-physics” hydrodynamical simulations of galaxy formation in the normal-branch Dvali-Gabadadze-Porrati (nDGP) braneworld model using a new modified version of the Arepo code and the IllustrisTNG galaxy formation model. We simulate two nDGP models (N5 and N1) which represent, respectively, weak and moderate departures from GR, in boxes of sizes 62 h−1Mpc and 25 h−1Mpc using 2 × 5123 dark matter particles and initial gas cells. This allows us to explore, for the first time, the impact of baryonic physics on galactic scales in braneworld models of modified gravity and to make predictions on the stellar content of dark matter haloes and galaxy evolution through cosmic time in these models. We find significant differences between the GR and nDGP models in the power spectra and correlation functions of gas, stars and dark matter of up to ∼25 per cent on large scales. Similar to their impact in the standard cosmological model (ΛCDM), baryonic effects can have a significant influence over the clustering of the overall matter distribution, with a sign that depends on scale. Studying the degeneracy between modified gravity and galactic feedback in these models, we find that these two physical effects on matter clustering can be cleanly disentangled, allowing for a method to accurately predict the matter power spectrum with baryonic effects included, without having to run hydrodynamical simulations. Depending on the braneworld model, we find differences compared with GR of up to ∼15 per cent in galaxy properties such as the stellar-to-halo-mass ratio, galaxy stellar mass function, gas fraction and star formation rate density. The amplitude of the fifth force is reduced by the presence of baryons in the very inner part of haloes, but this reduction quickly becomes negligible above ∼0.1 times the halo radius.

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“…The past decade has seen an increasing interest in such theories, leading to a large body of literature on their cosmological behaviours and possible observational tests. However, there has been little work on hydrodynamical simulations of non-standard gravity models (e.g., Arnold et al 2014Arnold et al , 2015Hammami et al 2015;He & Li 2016;Arnold et al 2016;Ellewsen et al 2018;. Exploring the effect of modified gravity on galactic scales in a cosmological context hence remains an important open topic that requires more quantitative work.…”

Section: Introductionmentioning

confidence: 99%

Galaxy formation in the brane world I: overview and first results

Hernández-Aguayo,

Arnold,

et al. 2020

Preprint

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We carry out "full-physics" hydrodynamical simulations of galaxy formation in the normalbranch Dvali-Gabadadze-Porrati (nDGP) braneworld model using a new modified version of the AREPO code and the IllustrisTNG galaxy formation model. We simulate two nDGP models (N5 and N1) which represent, respectively, weak and moderate departures from GR, in boxes of sizes 62 h −1 Mpc and 25 h −1 Mpc using 2 × 512 3 dark matter particles and initial gas cells. This allows us to explore, for the first time, the impact of baryonic physics on galactic scales in braneworld models of modified gravity and to make predictions on the stellar content of dark matter haloes and galaxy evolution through cosmic time in these models. We find significant differences between the GR and nDGP models in the power spectra and correlation functions of gas, stars and dark matter of up to ∼ 25 per cent on large scales. Similar to their impact in the standard cosmological model (ΛCDM), baryonic effects can have a significant influence over the clustering of the overall matter distribution, with a sign that depends on scale. Studying the degeneracy between modified gravity and galactic feedback in these models, we find that these two physical effects on matter clustering can be cleanly disentangled, allowing for a method to accurately predict the matter power spectrum with baryonic effects included, without having to run hydrodynamical simulations. Depending on the braneworld model, we find differences compared with GR of up to ∼ 15 per cent in galaxy properties such as the stellar-to-halo-mass ratio, galaxy stellar mass function, gas fraction and star formation rate density. The amplitude of the fifth force is reduced by the presence of baryons in the very inner part of haloes, but this reduction quickly becomes negligible above ∼ 0.1 times the halo radius.

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Degeneracies between modified gravity and baryonic physics

Cited by 4 publications

References 56 publications

Breaking cosmic degeneracies: Disentangling neutrinos and modified gravity with kinematic information

Breaking cosmic degeneracies: Disentangling neutrinos and modified gravity with kinematic information

Galaxy formation in the brane world I: overview and first results

Galaxy formation in the brane world I: overview and first results

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