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Orientation bias of optically selected galaxy clusters and its impact on stacked weak-lensing analyses

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posted on 2023-06-08, 21:00 authored by Jörg P Dietrich, Yuanyuan Zhang, Jeeseon Song, Christopher P Davis, Timothy A McKay, Leon Baruah, Matthew Becker, Christophe Benoist, Michael Busha, Luiz A N da Costa, Jiangang Hao, Marcio A G Maia, Christopher J Miller, Ricardo Ogando, Kathy RomerKathy Romer, Eduardo Rozo, Eli Rykoff, Risa Wechsler
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.

Funding

2012 Doctoral Training Grant - Quota Studentships (STFC); G0939; STFC-SCIENCE AND TECHNOLOGY FACILITIES COUNCIL; ST/K502364/1

Astronomy rolling grant; G0278; STFC-SCIENCE AND TECHNOLOGY FACILITIES COUNCIL; ST/I000976/1

History

Publication status

  • Published

File Version

  • Published version

Journal

Monthly Notices of the Royal Astronomical Society

ISSN

0035-8711

Publisher

Wiley-Blackwell

Volume

443

Page range

1713-1722

Department affiliated with

  • Physics and Astronomy Publications

Full text available

  • Yes

Peer reviewed?

  • Yes

Legacy Posted Date

2015-06-07

First Open Access (FOA) Date

2015-06-07

First Compliant Deposit (FCD) Date

2015-06-07

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