The resummation model in FLAMINGO: precisely predicting matter power suppression from observed halo baryon fractions

Monthly Notices of the Royal Astronomical Society, vol. 545

Abstract

ABSTRACT In order to derive unbiased cosmological parameters from Stage-IV surveys, we need models that can predict the matter power spectrum for at least $k\, {\lesssim }\, {10}\, h\mathrm{\, Mpc^{-1}}$ with per cent-level accuracy. The main challenge in this endeavour is that baryonic feedback significantly redistributes matter on large scales, but to an unknown degree. Here, we present an improved version of the ‘resummation’ model, which maps observed halo baryon fractions of massive haloes ($M_{\mathrm{500c}}\gtrsim 10^{12.5}\, \mathrm{M_\odot }$) to a flexible suppression signal, i.e. the ratio of baryonic to dark-matter-only (DMO) matter power spectra, using zero free parameters. We calibrate this model to the FLAMINGO hydrodynamical simulations, obtaining a typical accuracy of $\lesssim 1~{{\ \rm per\ cent}}$ for $k\, {\le }\, {10}\, h\mathrm{\, Mpc^{-1}}$ given mean halo baryon fractions within the spherical overdensity radii $R_{\mathrm{500c}}$ and $R_{\mathrm{200m}}$. When only those within $R_{\mathrm{500c}}$ are available, we still obtain $\lesssim 2~{{\ \rm per\ cent}}$ accuracy. We show that given small-scale stellar mass fractions, the model can be extended to yield $\lesssim 3~{{\ \rm per\ cent}}$ accurate suppression signals for all scales measured ($k\, {\le }\, {25}\, h\mathrm{\, Mpc^{-1}}$). We also extend the model to redshifts $z>0$. Central to the model is a seemingly mass-independent and feedback-independent relation that allows observed halo masses to be mapped to equivalent DMO halo masses using only observed mean halo baryon fractions, to $\lesssim 1~{{\ \rm per\ cent}}$ accuracy. This relation can also be used to retrieve the DMO halo mass function from observed halo masses and baryon fractions with per cent-level accuracy, without any assumptions on the strength of feedback. A Python package implementing the resummation model is made publicly available.

Authors 7

1. Marcel P. van Daalen corresponding Aachen Leiden Observatory

   Leiden University · Leiden Observatory

   Affiliation as printed

   Leiden Observatory, Leiden University , PO Box 9513, NL-2300 RA Leiden ,

   Leiden Observatory, Leiden University, PO Box 9513, NL-2300 RA Leiden, The Netherlands

2. Ioannis Koutalios Aachen Leiden Observatory

   Leiden University · Leiden Observatory

   Affiliation as printed

   Leiden Observatory, Leiden University , PO Box 9513, NL-2300 RA Leiden ,

   Leiden Observatory, Leiden University, PO Box 9513, NL-2300 RA Leiden, The Netherlands

3. Jeger C. Broxterman Aachen Leiden Observatory Lorentz Institute for Theoretical Physics

   Leiden University · Leiden Observatory

   Affiliation as printed

   Leiden Observatory, Leiden University , PO Box 9513, NL-2300 RA Leiden ,

   Lorentz Institute for Theoretical Physics, Leiden University , PO Box 9506, NL-2300 RA Leiden ,

   Lorentz Institute for Theoretical Physics, Leiden University, PO Box 9506, NL-2300 RA Leiden, The Netherlands

4. Bart J H Wolfs Aachen Leiden Observatory

   Leiden University · Leiden Observatory

   Affiliation as printed

   Leiden Observatory, Leiden University , PO Box 9513, NL-2300 RA Leiden ,

   Leiden Observatory, Leiden University, PO Box 9513, NL-2300 RA Leiden, The Netherlands

5. John C Helly

   Durham University

   Affiliation as printed

   Institute for Computational Cosmology, University of Durham Department of Physics, , South Road, Durham DH1 3LE ,

   Institute for Computational Cosmology, Department of Physics, University of Durham, South Road, Durham, DH1 3LE, UK

6. Matthieu Schaller Aachen Leiden Observatory Lorentz Institute for Theoretical Physics

   Leiden University · Leiden Observatory

   Affiliation as printed

   Leiden Observatory, Leiden University , PO Box 9513, NL-2300 RA Leiden ,

   Lorentz Institute for Theoretical Physics, Leiden University , PO Box 9506, NL-2300 RA Leiden ,

   Leiden Observatory, Leiden University, PO Box 9513, NL-2300 RA Leiden, The Netherlands

7. Joop Schaye Aachen Leiden Observatory

   Leiden University · Leiden Observatory

   Affiliation as printed

   Leiden Observatory, Leiden University , PO Box 9513, NL-2300 RA Leiden ,

   Leiden Observatory, Leiden University, PO Box 9513, NL-2300 RA Leiden, The Netherlands