Abstract
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 BAryons and HAloes of MAssive Systems 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 an $\sim 1{{\ \rm per\ cent}}$ 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 $1{{\ \rm per\ cent}}$ for $k\lt 1\, h\, \mathrm{Mpc}^{-1}$, 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.
Highlights
Current and near-future weak lensing surveys like DES,1 LSST,2 Euclid,3 and WFIRST4 face a significant challenge when attempting to interpret their measurements: they require predictions of the matter power spectrum with a precision better than 1 per cent (Huterer & Takada 2005; Ivezicet al. 2008; Laureijs 2009)
While we do not show so here, assuming a continuous star formation law somewhat diminishes the effect that the SNe have on the power spectrum, and increasing the mass loading instead of the wind speed barely changes the matter clustering at z = 0 compared to the fiducial model (‘REF’)
As shown by van Daalen & Schaye (2015), the dominant contribution to the power spectrum on scales k 20 h Mpc−1 comes from groups and clusters (M 1013.5 h−1 M ), which provide almost all the signal on scales k ≈ 1 h Mpc−1 – and the properties of groups and clusters are well reproduced by the AGN feedback in both OWLS and BARYONS AND HALOES OF MASSIVE SYSTEMS (BAHAMAS)
Summary
Current and near-future weak lensing surveys like DES, LSST, Euclid, and WFIRST4 face a significant challenge when attempting to interpret their measurements: they require predictions of the matter power spectrum with a precision better than 1 per cent (Huterer & Takada 2005; Ivezicet al. 2008; Laureijs 2009). While the underlying model in simulations with AGN is the same in each of the simulations presented here, many variations with different feedback strengths and/or scalings are explored, including some that go beyond what is expected to be realistic in order to allow sufficient flexibility for emulators and marginalization schemes Using these power spectra, we attempt to deepen our understanding of how feedback influences the clustering of matter, and how this depends on some of the choices made when running the simulations.
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