Cosmology with velocity dispersion counts: an alternative to measuring cluster halo masses

Abstract

The evolution of galaxy cluster counts is a powerful probe of several fundamental cosmological parameters. A number of recent studies using this probe have claimed tension with the cosmology preferred by the analysis of the Planck primary CMB data, in the sense that there are fewer clusters observed than predicted based on the primary CMB cosmology. One possible resolution to this problem is systematic errors in the absolute halo mass calibration in cluster studies, which is required to convert the standard theoretical prediction (the halo mass function) into counts as a function of the observable (e.g., X-ray luminosity, Sunyaev-Zel'dovich flux, optical richness). Here we propose an alternative strategy, which is to directly compare predicted and observed cluster counts as a function of the one-dimensional velocity dispersion of the cluster galaxies. We argue that the velocity dispersion of groups/clusters can be theoretically predicted as robustly as mass but, unlike mass, it can also be directly observed, thus circumventing the main systematic bias in traditional cluster counts studies. With the aid of the BAHAMAS suite of cosmological hydrodynamical simulations, we demonstrate the potential of the velocity dispersion counts for discriminating even similar $\Lambda$CDM models. These predictions can be compared with the results from existing redshift surveys such as the highly-complete Galaxy And Mass Assembly (GAMA) survey, and upcoming wide-field spectroscopic surveys such as the Wide Area Vista Extragalactic Survey (WAVES) and the Dark Energy Survey Instrument (DESI).

15 pages, 13 figures. Accepted for publication in MNRAS. New section on cosmological forecasts added

References in corpus (12)

• Massive neutrinos and cosmology
• The effect of photo-ionization on the cooling rates of enriched, astrophysical plasmas
• Chemical enrichment in cosmological, smoothed particle hydrodynamics simulations
• The BAHAMAS project: Calibrated hydrodynamical simulations for large-scale structure cosmology
• Virial Scaling of Massive Dark Matter Halos: Why Clusters Prefer a High Normalization Cosmology
• The relation between velocity dispersion and mass in simulated clusters of galaxies: dependence on the tracer and the baryonic physics
• Quantifying discordance in the 2015 Planck CMB spectrum
• Constraining the Scatter in the Mass-Richness Relation of maxBCG Clusters With Weak Lensing and X-ray Data
• The clustering of galaxies in the SDSS-III Baryon Oscillation Spectroscopic Survey: Signs of neutrino mass in current cosmological datasets
• The extended ROSAT-ESO Flux Limited X-ray Galaxy Cluster Survey (REFLEX II) IV. X-ray Luminosity Function and First Constraints on Cosmological Parameters
• Evidence for the inside-out growth of the stellar mass distribution in galaxy clusters since z~1
• A derivation of masses and total luminosities of galaxy groups and clusters in the maxBCG catalogue

Cited by in corpus (14)

• The BAHAMAS project: the CMB--large-scale structure tension and the roles of massive neutrinos and galaxy formation
• Deep Extragalactic VIsible Legacy Survey (DEVILS): Motivation, Design and Target Catalogue
• The scatter and evolution of the global hot gas properties of simulated galaxy cluster populations
• Testing for X-ray-SZ Differences and Redshift Evolution in the X-ray Morphology of Galaxy Clusters
• The Cluster-EAGLE project: velocity bias and the velocity dispersion - mass relation of cluster galaxies
• An application of machine learning techniques to galaxy cluster mass estimation using the MACSIS simulations
• An empirical measurement of the Halo Mass Function from the combination of GAMA DR4, SDSS DR12, and REFLEX II data
• Exploring Relations Between BCG \& Cluster Properties in the SPectroscopic IDentification of eROSITA Sources Survey from $0.05<z<0.3$
• The Cluster-EAGLE project: a comparison of dynamical mass estimators using simulated clusters
• Calibrating the Planck Cluster Mass Scale with Cluster Velocity Dispersions
• The Importance of Being Interpretable: Toward An Understandable Machine Learning Encoder for Galaxy Cluster Cosmology
• The Velocity Distribution Function of Galaxy Clusters as a Cosmological Probe
• Cluster Cosmology with the Velocity Distribution Function of the HeCS-SZ Sample
• Galaxy Velocity Bias in Cosmological Simulations: Towards Percent-level Calibration