Baryonic feedback and intrinsic alignments in profile: a frequentist view of DES Y3 cosmic shear
Abstract
Current cosmic shear surveys primarily constrain S8 and Ωm, while most other model parameters remain dominated by priors. Consequently, marginal posteriors are vulnerable to prior-volume effects, particularly through degeneracies among S8, baryonic feedback, and intrinsic alignment (IA) model parameters. To isolate data-driven constraints from prior volume effects, we compare profile likelihoods with Bayesian posteriors for DES Y3 cosmic shear under the DES Y3+KiDS-1000 Hybrid model. For cosmic shear alone, the profile global best fit and the marginal posterior mean agree in S8, but the profile likelihood reveals a strong degeneracy between feedback strength and S8, leaving the upper 1σ limit on S8 determined by the assumed feedback range. External CMB information on parameters other than Ωm and S8 breaks this degeneracy, suppressing prior-volume effects and reconciling the profiles with the posteriors. With CMB data included, small-scale cosmic shear data prefers moderate baryonic feedback strengths consistent with hydrodynamical simulations calibrated to observed gas fractions. Furthermore, additional unconstrained parameters in the tidal alignment and tidal torquing (TATT) model result in weaker constraints, shifting and broadening the S8 profile relative to the nonlinear linear alignment (NLA) model. Adding DES Y3 shear ratios mitigates this degeneracy, bringing profile likelihood and marginal posteriors into close agreement.
Related
- A two-component profile of baryonic feedback: hydrostatic and diffuse gas
- The VariableTNG project: Mass-dependent regulation of galaxy morphology by baryonic feedback
- Extracting intrinsic alignments in the Dark Energy Survey’s year 1 data, using the self-calibration method and LSST-DESC tools
- Model-Independent Assessments of Tidal Alignment and Density-Weighting Dependence in Galaxy Intrinsic Alignments
- Impact of galaxy intrinsic alignments on non-Gaussian weak lensing statistics for modified gravity
BibTeX
@misc{ganguly2026baryonic,
title = {{Baryonic feedback and intrinsic alignments in profile: a frequentist view of DES Y3 cosmic shear}},
author = {Anoma Ganguly and Elisabeth Krause and Tanvi Karwal and Vivian Miranda},
howpublished = {arXiv},
year = {2026},
month = nov,
doi = {10.48550/arxiv.2611.03537},
eprint = {2611.03537},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2611.03537},
note = {CC BY 4.0},
}
RIS
TY - UNPB
TI - Baryonic feedback and intrinsic alignments in profile: a frequentist view of DES Y3 cosmic shear
AU - Anoma Ganguly
AU - Elisabeth Krause
AU - Tanvi Karwal
AU - Vivian Miranda
PY - 2026
DA - 2026/11/02
PB - arXiv
DO - 10.48550/arxiv.2611.03537
UR - https://arxiv.org/abs/2611.03537
AB - Current cosmic shear surveys primarily constrain S_8 and Ω_m, while most other model parameters remain dominated by priors. Consequently, marginal posteriors are vulnerable to prior-volume effects, particularly through degeneracies among S_8, baryonic feedback, and intrinsic alignment (IA) model parameters. To isolate data-driven constraints from prior volume effects, we compare profile likelihoods with Bayesian posteriors for DES Y3 cosmic shear under the DES Y3+KiDS-1000 Hybrid model. For cosmic shear alone, the profile global best fit and the marginal posterior mean agree in S_8, but the profile likelihood reveals a strong degeneracy between feedback strength and S_8, leaving the upper 1σ limit on S_8 determined by the assumed feedback range. External CMB information on parameters other than Ω_m and S_8 breaks this degeneracy, suppressing prior-volume effects and reconciling the profiles with the posteriors. With CMB data included, small-scale cosmic shear data prefers moderate baryonic feedback strengths consistent with hydrodynamical simulations calibrated to observed gas fractions. Furthermore, additional unconstrained parameters in the tidal alignment and tidal torquing (TATT) model result in weaker constraints, shifting and broadening the S_8 profile relative to the nonlinear linear alignment (NLA) model. Adding DES Y3 shear ratios mitigates this degeneracy, bringing profile likelihood and marginal posteriors into close agreement.
ER -