Tessore, N;
Joachimi, B;
Loureiro, A;
Hall, A;
Cañas-Herrera, G;
Tutusaus, I;
Jeffrey, N;
... Sellentin, E; + view all
(2025)
Euclid preparation: LIX. Angular power spectra from discrete observations.
Astronomy and Astrophysics
, 694
, Article A141. 10.1051/0004-6361/202452018.
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Abstract
In this paper we present the framework for measuring angular power spectra in the Euclid mission. The observables in galaxy surveys, such as galaxy clustering and cosmic shear, are not continuous fields, but discrete sets of data, obtained only at the positions of galaxies. We show how to compute the angular power spectra of such discrete data sets, without treating observations as maps of an underlying continuous field that is overlaid with a noise component. This formalism allows us to compute the exact theoretical expectations for our measured spectra, under a number of assumptions that we track explicitly. In particular, we obtain exact expressions for the additive biases (‘shot noise’) in angular galaxy clustering and cosmic shear. For efficient practical computations, we introduce a spin-weighted spherical convolution with a well-defined convolution theorem, which allows us to apply exact theoretical predictions to finite-resolution maps, including HEALPix. When validating our methodology, we find that our measurements are biased by less than 1% of their statistical uncertainty in simulations of Euclid’s first data release.
| Type: | Article |
|---|---|
| Title: | Euclid preparation: LIX. Angular power spectra from discrete observations |
| Open access status: | An open access version is available from UCL Discovery |
| DOI: | 10.1051/0004-6361/202452018 |
| Publisher version: | https://doi.org/10.1051/0004-6361/202452018 |
| Language: | English |
| Additional information: | © The Authors 2025 Licence Creative CommonsOpen Access article, published by EDP Sciences, under the terms of the Creative Commons Attribution License (https://creativecommons.org/licenses/by/4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. This article is published in open access under the Subscribe to Open model. Subscribe to A&A to support open access publication. |
| Keywords: | Methods: statistical; Surveys; Cosmology: observations; large-scale structure of Universe; Gravitational lensing: weak |
| UCL classification: | UCL UCL > Provost and Vice Provost Offices > UCL BEAMS UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences > Dept of Physics and Astronomy UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences > Dept of Space and Climate Physics |
| URI: | https://discovery.ucl.ac.uk/id/eprint/10206498 |
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