Galaxy Cluster Mass Reconstruction Project – IV. Understanding the effects of imperfect membership on cluster mass estimation

Wojtak, R.; Old, L.; Mamon, G.A.; Pearce, frF.R.; de Carvalho, R.; Sifón, C.; Gray, M.E.; Skibba, R.A.; Croton, D.; Bamford, Steven; Gifford, D.; von der Linden, A.; Muñoz-Cuartas, J.C.; Müller, V.; Pearson, R.J.; Rozo, E.; Rykoff, E.; Saro, A.; Sepp, T.; Tempel, E.

Abstract

The primary difficulty in measuring dynamical masses of galaxy clusters from galaxy data lies in the separation between true cluster members from interloping galaxies along the line of sight. We study the impact of membership contamination and incompleteness on cluster mass estimates obtained with 25 commonly used techniques applied to nearly 1000 mock clusters with precise spectroscopic redshifts. We show that all methods overestimate or underestimate cluster masses when applied to contaminated or incomplete galaxy samples, respectively. This appears to be the main source of the intrinsic scatter in the mass scaling relation. Applying corrections based on a prior knowledge of contamination and incompleteness can reduce the scatter to the level of shot noise expected for poorly sampled clusters. We establish an empirical model quantifying the effect of imperfect membership on cluster mass estimation and discuss its universal and method-dependent features. We find that both imperfect membership and the response of the mass estimators depend on cluster mass, effectively causing a flattening of the estimated–true mass relation. Imperfect membership thus alters cluster counts determined from spectroscopic surveys, hence the cosmological parameters that depend on such counts.

Citation

Wojtak, R., Old, L., Mamon, G., Pearce, F., de Carvalho, R., Sifón, C., …Tempel, E. (2018). Galaxy Cluster Mass Reconstruction Project – IV. Understanding the effects of imperfect membership on cluster mass estimation. Monthly Notices of the Royal Astronomical Society, 481(1), 324-340. https://doi.org/10.1093/mnras/sty2257

• Journal Article Type: Article
• Acceptance Date: Aug 15, 2018
• Online Publication Date: Aug 18, 2018
• Publication Date: Nov 21, 2018
• Deposit Date: Sep 27, 2018
• Publicly Available Date: Sep 27, 2018
• Journal: Monthly Notices of the Royal Astronomical Society
• Print ISSN: 0035-8711
• Electronic ISSN: 1365-2966
• Publisher: Oxford University Press
• Peer Reviewed: Peer Reviewed
• Volume: 481
• Issue: 1
• Pages: 324-340
• DOI: https://doi.org/10.1093/mnras/sty2257
• Keywords: methods: numerical, methods: statistical, galaxies: clusters: general, galaxies: haloes, galaxies: kinematics and dynamics, cosmology: observations
• Public URL: https://nottingham-repository.worktribe.com/output/1137630
• Publisher URL: https://academic.oup.com/mnras/article/481/1/324/5076075
• Additional Information: This article has been accepted for publication in Monthly Notices of the Royal Astronomical Society © 2018 The Author(s) Published by Oxford University Press on behalf of the Royal Astronomical Society. All rights reserved.
• Contract Date: Sep 27, 2018