The Three Hundred Project: Correcting for the hydrostatic-equilibrium mass bias in X-ray and SZ surveys

¹ Department of Physics, Shahid Beheshti University, G.C., Evin, Tehran 19839, Iran
e-mail: s_ansarifard@sbu.ac.ir
² Dipartimento di Fisica, Sezione di Astronomia, Università di Trieste, via Tiepolo 11, 34143 Trieste, Italy
³ INAF–Osservatorio Astronomico Trieste, via Tiepolo 11, 34123 Trieste, Italy
e-mail: elena.rasia@inaf.it
⁴ Institute of Fundamental Physics of the Universe, via Beirut 2, 34151 Grignano, Trieste, Italy
⁵ Harvard-Smithsonian Center for Astrophysics, 60 Garden St., Cambridge, MA 02138, USA
⁶ Universitäts-Sternwarte München, Scheinerstr. 1, 81679 München, Germany
⁷ INFN, Instituto Nazionale di Fisica Nucleare, Trieste, Italy
⁸ Institute for Astronomy, University of Edinburgh, Royal Observatory, Edinburgh EH9 3HJ, UK
⁹ Dipartimento di Fisica, Sapienza Università di Roma, p.le Aldo Moro 5, 00185 Rome, Italy
¹⁰ Max Planck Institut for Astrophysics, 85748 Garching, Germany
¹¹ INAF, Osservatorio di Astrofisica e Scienza dello Spazio, via Pietro Gobetti 93/3, 40129 Bologna, Italy
¹² INFN, Sezione di Bologna, viale Berti Pichat 6/2, 40127 Bologna, Italy
¹³ Departamento de Física Teórica M-8, Universidad Autónoma de Madrid, Cantoblanco 28049, Madrid, Spain
¹⁴ Centro de Investigación Avanzada en Física Fundamental (CIAFF), Facultad de Ciencias, Universidad Autónoma de Madrid, Cantoblanco 28049, Madrid, Spain

Received: 19 September 2019
Accepted: 18 November 2019

Abstract

Accurate and precise measurement of the masses of galaxy clusters is key to deriving robust constraints on cosmological parameters. However, increasing evidence from observations confirms that X-ray masses obtained under the assumption of hydrostatic equilibrium might be underestimated, as previously predicted by cosmological simulations. We analyze more than 300 simulated massive clusters from the Three Hundred Project, and investigate the connection between mass bias and several diagnostics extracted from synthetic X-ray images of these simulated clusters. We find that the azimuthal scatter measured in 12 sectors of the X-ray flux maps is a statistically significant indication of the presence of an intrinsic (i.e., 3D) clumpy gas distribution. We verify that a robust correction to the hydrostatic mass bias can be inferred when estimates of the gas inhomogeneity from X-ray maps (such as the azimuthal scatter or the gas ellipticity) are combined with the asymptotic external slope of the gas density or pressure profiles, which can be respectively derived from X-ray and millimeter (Sunyaev-Zeldovich effect) observations. We also obtain that mass measurements based on either gas density and temperature or gas density and pressure result in similar distributions of the mass bias. In both cases, we provide corrections that help reduce both the dispersion and skewness of the mass bias distribution. These are effective even when irregular clusters are included leading to interesting implications for the modeling and correction of hydrostatic mass bias in cosmological analyses of current and future X-ray and SZ cluster surveys.