How baryons can significantly bias cluster count cosmology

ABSTRACT We quantify two main pathways through which baryonic physics biases cluster count cosmology. create mock samples that reproduce the baryon content inferred from X-ray observations. link clusters to their counterparts in a dark matter-only universe, whose abundances can be predicted robustly, by assuming matter density profile is not significantly affected baryons. derive weak lensing halo masses and infer best-fitting cosmological parameters ?m, S8 = ?8(?m/0.3)0.2, w0 sample. find because of need accommodate change due ejection baryons, mass calibrations are only unbiased if concentration left free when fitting reduced shear with NFW profiles. However, even total estimates give rise biased measured functions compared predictions simulations. This bias dominates for haloes $m_\mathrm{500c} \lt 10^{14.5} \, \rm h^{-1} \mathrm{M_\odot }$. For stage IV-like survey without estimation uncertainties, an area $\approx 15\,000 \mathrm{deg^2}$ constant cut $m_\mathrm{200m,min} 10^{14} \,\rm }$, $-11 \pm 1 \mathrm{per\, cent}$ $-3.29 0.04 S8, $9 1.5 w0. The statistical significance depends on how accurately actual uncertainty individual known. suggest rather than mass, (re-scaled) combination observations hot gas, should used