How baryons can significantly bias cluster count cosmology

Abstract

We quantify two main pathways through which baryonic physics biases cluster count cosmology. We create mock cluster samples that reproduce the baryon content inferred from X-ray observations. We link clusters to their counterparts in a dark matter-only universe, whose abundances can be predicted robustly, by assuming the dark matter density profile is not significantly affected by baryons. We derive weak lensing halo masses and infer the best-fitting cosmological parameters ${\Omega }_{\mathrm{m}}$, $S_8={\sigma }_8({\Omega }_{\mathrm{m}}/0.3{)}^{0.2}$, and $w_0$ from the mock cluster sample. We find that because of the need to accommodate the change in the density profile due to the ejection of baryons, weak lensing mass calibrations are only unbiased if the concentration is left free when fitting the reduced shear with NFW profiles. However, even unbiased total mass estimates give rise to biased cosmological parameters if the measured mass functions are compared with predictions from dark matter-only simulations. This bias dominates for haloes with $m_{500c}<10^{14.5}{h}^{-1}{\mathrm{M}}_{\odot }$. For a stage IV-like cluster survey without mass estimation uncertainties, an area $\approx 15000\mathrm{de}{\mathrm{g}}^2$ and a constant mass cut of $m_{200m,\min }=10^{14}{h}^{-1}{\mathrm{M}}_{\odot }$, the biases are $-11\pm 1\%$ in ${\Omega }_{\mathrm{m}}$, $-3.29\pm 0.04\%$ in $S_8$, and $9\pm 1.5\%$ in $w_0$. The statistical significance of the baryonic bias depends on how accurately the actual uncertainty on individual cluster mass estimates is known. We suggest that rather than the total halo mass, the (re-scaled) dark matter mass inferred from the combination of weak lensing and observations of the hot gas, should be used for cluster count cosmology.

17 pages, 11 figures. Updated wrong definition of spherical overdensity mass m200m, our calculations used the correct definition, as can be seen from the publicly-available code at https://github.com/StijnDebackere/lensing_haloes/blob/afe4f8699003/lensing_haloes/results.py#L311-L321 . Mock data, including cosmology MAPs, available at https://doi.org/10.5281/zenodo.4469436

References in corpus (13)

• The Canadian Cluster Comparison Project: detailed study of systematics and updated weak lensing masses
• Baryon effects on the internal structure of LCDM halos in the EAGLE simulations
• The Representative XMM-Newton Cluster Structure Survey (REXCESS) of an X-ray Luminosity Selected Galaxy Cluster Sample
• Upper limits on the rates of binary neutron star and neutron-star--black-hole mergers from Advanced LIGO's first observing run
• The abundance of (not just) dark matter haloes
• The impact of baryons on massive galaxy clusters: halo structure and cluster mass estimates
• On the impact of baryons on the halo mass function, bias, and cluster cosmology
• Evidence for the inside-out growth of the stellar mass distribution in galaxy clusters since z~1
• Planck Sunyaev-Zel'dovich Cluster Mass Calibration using Hyper Suprime-Cam Weak Lensing
• Connecting the structure of dark matter haloes to the primordial power spectrum
• Disturbed galaxy clusters are more abundant in an X-ray volume-limited sample
• Counts of galaxy clusters as cosmological probes: the impact of baryonic physics
• CoMaLit -- VI. Intrinsic scatter in stacked relations. The weak lensing AMICO galaxy clusters in KiDS-DR3

Cited by in corpus (25)

• The FLAMINGO project: cosmological hydrodynamical simulations for large-scale structure and galaxy cluster surveys
• Simulating Groups and the IntraGroup Medium: The Surprisingly Complex and Rich Middle Ground Between Clusters and Galaxies
• Detecting Neutrino Mass by Combining Matter Clustering, Halos, and Voids
• How baryons affect halos and large-scale structure: a unified picture from the Simba simulation
• Calibration of bias and scatter involved in cluster mass measurements using optical weak gravitational lensing
• SP(k) -- A hydrodynamical simulation-based model for the impact of baryon physics on the non-linear matter power spectrum
• KiDS-1000: Combined halo-model cosmology constraints from galaxy abundance, galaxy clustering and galaxy-galaxy lensing
• Optical selection bias and projection effects in stacked galaxy cluster weak lensing
• Offset between X-ray and optical centers in clusters of galaxies: connecting eROSITA data and simulations
• Euclid preparation. XXXII. Evaluating the weak lensing cluster mass biases using the Three Hundred Project hydrodynamical simulations
• EAGLE-like simulation models do not solve the entropy core problem in groups and clusters of galaxies
• Cluster counts III. $\Lambda$CDM extensions and the cluster tension
• Towards 1% accurate galaxy cluster masses: Including baryons in weak-lensing mass inference
• The halo model with beyond-linear halo bias: unbiasing cosmological constraints from galaxy-galaxy lensing and clustering
• The BAHAMAS project: Evaluating the accuracy of the halo model in predicting the non-linear matter power spectrum
• Why are we still using 3D masses for cluster cosmology?
• Galaxy cluster aperture masses are more robust to baryonic effects than 3D halo masses
• Halo Growth and Merger Rates as a Cosmological Test
• The infall region as a complementary probe to cluster abundance
• Cluster Assembly Times as a Cosmological Test
• Cosmological constraints from galaxy clustering and galaxy-galaxy lensing with extended SubHalo Abundance Matching
• The THREEHUNDRED project: the effect of baryon processes at galaxy cluster scale
• Weak lensing constraints on the stellar-to-halo mass relation of galaxy groups with simulation-informed scatter
• Towards a universal model for the density profiles of dark matter haloes
• Constraining cosmological parameters using density split lensing and the conditional stellar mass function