Yan, Ziang;
Wright, Angus H;
Chisari, Nora Elisa;
Georgiou, Christos;
Joudaki, Shahab;
Loureiro, Arthur;
Reischke, Robert;
... Yoon, Mijin; + view all
(2025)
KiDS-Legacy: Angular galaxy clustering from deep surveys with complex selection effects.
Astronomy & Astrophysics
, 694
, Article A259. 10.1051/0004-6361/202452808.
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Abstract
Photometric galaxy surveys, despite their limited resolution along the line of sight, encode rich information about the large-scale structure (LSS) of the Universe thanks to the high number density and extensive depth of the data. However, the complicated selection effects in wide and deep surveys can potentially cause significant bias in the angular two-point correlation function (2PCF) measured from those surveys. In this paper, we measure the 2PCF from the newly published KiDS-Legacy sample. Given an r-band 5σ magnitude limit of 24.8 and survey footprint of 1347 deg2, it achieves an excellent combination of sky coverage and depth for such a measurement. We find that complex selection effects, primarily induced by varying seeing, introduce over-estimation of the 2PCF by approximately an order of magnitude. To correct for such effects, we apply a machine learning-based method to recover an organised random (OR) that presents the same selection pattern as the galaxy sample. The basic idea is to find the selection-induced clustering of galaxies using a combination of self-organising maps (SOMs) and hierarchical clustering (HC). This unsupervised machine learning method is able to recover complicated selection effects without specifying their functional forms. We validate this SOM+HC method on mock deep galaxy samples with realistic systematics and selections derived from the KiDS-Legacy catalogue. Using mock data, we demonstrate that the OR delivers unbiased 2PCF cosmological parameter constraints, removing the 27σ offset in the galaxy bias parameter that is recovered when adopting uniform randoms. Blinded measurements on the real KiDS-Legacy data show that the corrected 2PCF is robust to the SOM+HC configuration near the optimal set-up suggested by the mock tests.
| Type: | Article |
|---|---|
| Title: | KiDS-Legacy: Angular galaxy clustering from deep surveys with complex selection effects |
| Open access status: | An open access version is available from UCL Discovery |
| DOI: | 10.1051/0004-6361/202452808 |
| Publisher version: | https://doi.org/10.1051/0004-6361/202452808 |
| Language: | English |
| Additional information: | Open 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: | Science & Technology, Physical Sciences, Astronomy & Astrophysics, methods: data analysis, methods: statistical, cosmological parameters, cosmology: observations, large-scale structure of Universe, DARK ENERGY SURVEY, COSMIC SHEAR, COSMOLOGY CONSTRAINTS, 2-POINT STATISTICS, SYSTEMATIC-ERRORS, POWER SPECTRUM, DATA RELEASE, SPACE, WIDE, REDSHIFTS |
| 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 |
| URI: | https://discovery.ucl.ac.uk/id/eprint/10206500 |
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