Exploring the effects of galaxy formation on matter clustering through a library of simulation power spectra

Abstract

Upcoming weak lensing surveys require a detailed theoretical understanding of the matter power spectrum in order to derive accurate and precise cosmological parameter values. While galaxy formation is known to play an important role, its precise effects are currently unknown. We present a set of 92 matter power spectra from the OWLS, cosmo-OWLS and bahamas simulation suites, including different ΛCDM cosmologies, neutrino masses, subgrid prescriptions and AGN feedback strengths. We conduct a detailed investigation of the dependence of the relative difference between the total matter power spectra in hydrodynamical and collisionless simulations on the effectiveness of stellar and AGN feedback, cosmology and redshift. The strength of AGN feedback can greatly affect the power on a range of scales, while a lack of stellar feedback can greatly increase the effectiveness of AGN feedback on large scales. We also examine differences in the initial conditions of hydrodynamic and N-body simulations that can lead to a ∼ 1% discrepancy in the large-scale power, and furthermore show our results to be insensitive to cosmic variance. We present an empirical model capable of predicting the effect of galaxy formation on the matter power spectrum at z = 0 to within 1% for k < 1 h Mpc −1 , given only the mean baryon fraction in galaxy groups. Differences in group baryon fractions can also explain the quantitative disagreement between predictions from the literature. All total and dark matter only power spectra in this library will be made publicly available at powerlib.strw.leidenuniv.nl.

Baryonic effects for weak lensing. Part I. Power spectrum and covariance matrix

“…However, it has become increasingly evident over the last few years that baryonic processes (which are ignored in gravity-only N -body simulations and associated regression techniques) have a significant effect on current and future weak-lensing observations. Several hydrodynamical simulations which include feedback effects from active galactic nuclei (AGN) and supernova explosions have shown that the clustering signal is affected by 10-30 percent at the nonlinear scales [16][17][18][19][20][21][22][23]. Similar effects have been found using the more analytical and physically intuitive approach of the halo model [24][25][26][27].…”

The BAHAMAS project: effects of dynamical dark energy on large-scale structure

“…In addition, it is well known that baryonic effects on the matter power spectrum are of the order of ∼10-20% and cause a suppression in the power spectrum at k > ∼ 0.1 Mpc −1 h (van Daalen et al 2011;Mummery et al 2017;Schneider et al 2019;van Daalen et al 2020;Debackere et al 2020). The DDE cosmologies considered here produce effects of similar magnitude, although they extend throughout the linear and non-linear regime and should therefore be distinguishable from baryonic effects given a wide enough range of well-sampled k values.…”

“…This has been shown with respect to the matter power spectrum (e.g. van Daalen et al 2011;Schneider et al 2019;van Daalen et al 2020), the halo mass function (e.g. Sawala et al 2013;Cusworth et al 2014;Velliscig et al 2014), clustering (van Daalen et al 2014, density profiles (e.g.…”

“…Additionally, baryons contribute a significant fraction of the total matter content of the Universe that is not modelled beyond the expansion history in the methods mentioned above. It has been shown that baryonic feedback processes not only affect the spatial distribution of baryons but also induce a back-reaction onto the dark matter distribution that should not be ignored (van Daalen et al 2011;Velliscig et al 2014;Mummery et al 2017;Springel et al 2018;Chisari et al 2018;McCarthy et al 2018;van Daalen et al 2020). Hence, hydrodynamical cosmological N-body simulations are the only method that can model the matter distribution accurately and self-consistently down to highly non-linear scales as well as accurately include the effects of baryons.…”

Baryonic effects for weak lensing. Part II. Combination with X-ray data and extended cosmologies

“…As already shown in the main text (see Figs. [6][7][8], there is a noticeable gain when adding external data from X-ray gas fractions, i.e when going from the…”