Baryonic feedback suppression of the matter power spectrum: a three-parameter fitting formula and its single-parameter reduction
Abstract
Baryonic feedback can suppress matter clustering by ∼ 10% at k∼ 1h/Mpc and z∼ 1, and is therefore a major source of systematic errors in weak lensing cosmology. We investigate this effect through the ratio S(k,z)≡ Phydro(k,z)/PDMO(k,z) measured in the FLAMINGO, IllustrisTNG, and Illustris hydrodynamical simulation suites, together with the one-parameter-at-a-time (1P) variation runs of CAMELS-TNG and CAMELS-SIMBA. We present a three-parameter fitting formula that reproduces all but one of these runs with maximum error less than $0.03$ (and typical error less than $0.01$) at k≤ 3h/Mpc and z≤ 2; the only exception is a run with unrealistically low Ωm=0.1. Each of the three parameters (B0, n, and a) has a clear physical interpretation: B0 sets the characteristic scale of the suppression at z=0, corresponding to a gas particle displacement scale of B01/2; n sets the suppression floor (1−Ωb/Ωm)n; and a sets the redshift zB at which the suppression peaks. Furthermore, we find that B0 and zB are significantly correlated for most runs. Also, n≃ 1 for FLAMINGO, TNG and CAMELS-TNG. For these simulations, the description reduces to a single parameter formula with maximum error less than $0.03$. The formulas remain accurate at max(|ΔS|)<0.03 (and typical error less than $0.01$) for cosmologies well away from the calibration cosmology, spanning the range Ωm∈ [0.2,0.5], Ωb∈ [0.029,0.069] and σ8∈ [0.6,1.0]. These results imply that, despite the diversity of baryonic physics implementations, an accurate description of S(k,z) requires at most three effective degrees of freedom. Therefore the impact of feedback on weak lensing cosmology can in principle be mitigated internally without significant loss of cosmological constraining power.
Related
- The suppression of the matter power spectrum: strong feedback from X-ray gas mass fractions, kSZ effect profiles, and galaxy–galaxy lensing
- The VariableTNG project: Mass-dependent regulation of galaxy morphology by baryonic feedback
- A two-component profile of baryonic feedback: hydrostatic and diffuse gas
- Baryonic feedback and intrinsic alignments in profile: a frequentist view of DES Y3 cosmic shear
- Constraining Baryonic Feedback at z∼ 1 with the Hα Luminosity Function
BibTeX
@misc{zhang2026baryonic,
title = {{Baryonic feedback suppression of the matter power spectrum: a three-parameter fitting formula and its single-parameter reduction}},
author = {Pengjie Zhang},
howpublished = {arXiv},
year = {2026},
month = sep,
doi = {10.48550/arxiv.2609.00807},
eprint = {2609.00807},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2609.00807},
note = {CC BY 4.0},
}
RIS
TY - UNPB
TI - Baryonic feedback suppression of the matter power spectrum: a three-parameter fitting formula and its single-parameter reduction
AU - Pengjie Zhang
PY - 2026
DA - 2026/09/01
PB - arXiv
DO - 10.48550/arxiv.2609.00807
UR - https://arxiv.org/abs/2609.00807
AB - Baryonic feedback can suppress matter clustering by ∼ 10% at k∼ 1h/Mpc and z∼ 1, and is therefore a major source of systematic errors in weak lensing cosmology. We investigate this effect through the ratio S(k,z)≡ P_hydro(k,z)/P_DMO(k,z) measured in the FLAMINGO, IllustrisTNG, and Illustris hydrodynamical simulation suites, together with the one-parameter-at-a-time (1P) variation runs of CAMELS-TNG and CAMELS-SIMBA. We present a three-parameter fitting formula that reproduces all but one of these runs with maximum error less than $0.03$ (and typical error less than $0.01$) at k≤ 3h/Mpc and z≤ 2; the only exception is a run with unrealistically low Ω_m=0.1. Each of the three parameters (B_0, n, and a) has a clear physical interpretation: B_0 sets the characteristic scale of the suppression at z=0, corresponding to a gas particle displacement scale of B_0^1/2; n sets the suppression floor (1−Ω_b/Ω_m)^n; and a sets the redshift z_B at which the suppression peaks. Furthermore, we find that B_0 and z_B are significantly correlated for most runs. Also, n≃ 1 for FLAMINGO, TNG and CAMELS-TNG. For these simulations, the description reduces to a single parameter formula with maximum error less than $0.03$. The formulas remain accurate at max(|ΔS|)<0.03 (and typical error less than $0.01$) for cosmologies well away from the calibration cosmology, spanning the range Ω_m∈ [0.2,0.5], Ω_b∈ [0.029,0.069] and σ_8∈ [0.6,1.0]. These results imply that, despite the diversity of baryonic physics implementations, an accurate description of S(k,z) requires at most three effective degrees of freedom. Therefore the impact of feedback on weak lensing cosmology can in principle be mitigated internally without significant loss of cosmological constraining power.
ER -