Impact of baryons in cosmic shear analyses with tomographic aperture mass statistics

Abstract

NonGaussian cosmic shear statistics based on weak-lensing aperture mass (Map) maps can outperform the classical shear two-point correlation function (γ-2PCF) in terms of cosmological constraining power. However, reaching the full potential of these new estimators requires accurate modeling of the physics of baryons as the extra nonGaussian information mostly resides at small scales. We present one such modeling based on the Magneticum hydrodynamical simulation for the KiDS-450 and DES-Y1 surveys and a Euclid-like survey. We compute the bias due to baryons on the lensing PDF and the distribution of peaks and voids in Map maps and propagate it to the cosmological forecasts on the structure growth parameter S8, the matter density parameter Ωm, and the dark energy equation of state w0 using the SLICS and cosmo-SLICS sets of dark-matter-only simulations. We report a negative bias of a few percent on S8 and Ωm and also measure a positive bias of the same level on w0 when including a tomographic decomposition. These biases reach ∼5% when combining Map statistics with the γ-2PCF as these estimators show similar dependency on the AGN feedback. We verify that these biases constitute a less than 1σ shift on the probed cosmological parameters for current cosmic shear surveys. However, baryons need to be accounted for at the percentage level for future Stage IV surveys and we propose to include the uncertainty on the AGN feedback amplitude by marginalizing over this parameter using multiple simulations such as those presented in this paper. Finally, we explore the possibility of mitigating the impact of baryons by filtering the Map map but find that this process would require suppressing the small-scale information to a point where the constraints would no longer be competitive.

Cosmic shear beyond 2-point statistics: Accounting for galaxy intrinsic alignment with projected tidal fields

“…1. With a lower level of shape noise and a significantly higher galaxy density compared to the KiDS-like catalogues, Martinet et al (2021a) find that 10 light-cones per cosmology is enough for their measurement (an analysis similar to ours but in the context of baryonic feedback). For all Euclid-like catalogues, five shape noise realisations are produced and averaged over in the end, to better capture the non-Gaussian signal.…”

“…We also explore the effect of IA on three non-Gaussian statistics constructed from aperture mass maps M ap (θ) (Schneider 1996). Closely following the measurement methods described in Martinet et al (2021b) and Martinet et al (2021a), these maps are constructed directly from the galaxy catalogues by stacking the tangential component of ellipticities around pixels at position θ, weighted by an aperture filter Q(θ, θ ap , x c ):…”

“…The cases labelled as 'M20' are extracted from table 1 and is evaluated by interpolating the measurements at the cosmo-SLICS nodes with radial basis functions. We follow the approach developed for hydrodynamical simulations in Martinet et al (2021a) and infuse the bias measured in the IA catalogues to the measurement data vector. This ensures that differences between the mocks used for the wCDM model and those used for IA infusion (for instance the different sampling of galaxy positions) are not biasing our model, nor our estimate of the resulting bias on cosmology.…”

“…Once again, IA are the strongest at low redshift and in cross-tomographic bins. Over-plotted on these measurements are the effect of baryonic feedback measured from the Magneticum simulations in Martinet et al (2021a), which unlike IA is approximately constant for all red-shift bins. Since the cosmological information extracted by lensing is the highest at high redshift, we could expect peak count statistics from deep surveys to be more affected by baryonic feedback than IA, however this conclusion could of course vary when considering models different from the δ-NLA and Magneticum.…”

“…In particular, the uncertainties associated to photometric redshifts, shape calibration/shear inference, baryonic feedback mechanism and intrinsic alignment (IA) of galaxies must be carefully dealt with for the inferred cosmology to be accurate. While the former two of these effects can be included in N-body simulations at the ray-tracing level, the impact of baryon feedback on lensing statistics beyond two-point statistics typically requires to be calibrated on hydrodynamical simulations (Osato et al 2015;Castro et al 2018;Martinet et al 2021a), although baryonification methods can also be of assistance (Schneider et al 2019;Weiss et al 2019;Lu & Haiman 2021).…”