Journal
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
Volume 443, Issue 2, Pages 1713-1722Publisher
OXFORD UNIV PRESS
DOI: 10.1093/mnras/stu1282
Keywords
gravitational lensing: weak; galaxies: clusters: general; cosmological parameters
Categories
Funding
- NSF [AST-0807304]
- US Department of Energy [DE-FG02-95ER40899, DE-AC02-76SF00515]
- US National Science Foundation
- Ministry of Science and Education of Spain
- Science and Technology Facilities Council of the United Kingdom
- Higher Education Funding Council for England
- National Center for Supercomputing Applications at the University of Illinois at Urbana-Champaign
- Kavli Institute of Cosmological Physics at the University of Chicago
- Financiadora de Estudos e Projetos
- Funda cao Carlos Chagas Filho de Amparo a Pesquisa do Estado do Rio de Janeiro
- Conselho Nacional de Desenvolvimento Cientifico e Tecnologico
- Ministerio da Ciencia e Tecnologia
- Deutsche Forschungsgemeinschaft
- Collaborating Institutions in the DES
- STFC [ST/H001581/1, ST/M003574/1, ST/I000976/1, ST/L006529/1, ST/L000652/1] Funding Source: UKRI
- Division Of Astronomical Sciences
- Direct For Mathematical & Physical Scien [1138737] Funding Source: National Science Foundation
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Weak-lensing measurements of the averaged shear profiles of galaxy clusters binned by some proxy for cluster mass are commonly converted to cluster mass estimates under the assumption that these cluster stacks have spherical symmetry. In this paper, we test whether this assumption holds for optically selected clusters binned by estimated optical richness. Using mock catalogues created from N-body simulations populated realistically with galaxies, we ran a suite of optical cluster finders and estimated their optical richness. We binned galaxy clusters by true cluster mass and estimated optical richness and measure the ellipticity of these stacks. We find that the processes of optical cluster selection and richness estimation are biased, leading to stacked structures that are elongated along the line of sight. We show that weak-lensing alone cannot measure the size of this orientation bias. Weak-lensing masses of stacked optically selected clusters are overestimated by up to 3-6 per cent when clusters can be uniquely associated with haloes. This effect is large enough to lead to significant biases in the cosmological parameters derived from large surveys like the Dark Energy Survey, if not calibrated via simulations or fitted simultaneously. This bias probably also contributes to the observed discrepancy between the observed and predicted Sunyaev-Zel'dovich signal of optically selected clusters.
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