Catalog-based pseudo-Cℓs

Journal article

We present a formalism to extract the angular power spectrum of fields sampled at a finite number of points with arbitrary positions — a common situation for several catalog-based astrophysical probes — through a simple extension of the standard pseudo-C_ℓ algorithm. A key complication in this case is the need to handle the shot noise component of the associated discrete angular mask which, for sparse catalogs, can lead to strong coupling between very different angular scales. We show that this problem can be solved easily by estimating this contribution analytically and subtracting it. The resulting estimator is immune to small-scale pixelization effects and aliasing, and, most notably, unbiased against the contribution from measurement noise uncorrelated between different sources. We demonstrate the validity of the method in the context of cosmic shear datasets, and showcase its usage in the case of other spin-0 and spin-1 astrophysical fields of interest. We incorporate the method in the public<monospace>NaMaster</monospace> code.

Authors: Wolz, K; Alonso, D; Nicola, A

• Publication status: Published
• Peer review status: Peer reviewed
• Publisher: IOP Publishing
• Journal: Journal of Cosmology and Astroparticle Physics
• Volume: 2025
• Issue: 1
• Article number: 028
• Publication date: 2025-01-09
• Acceptance date: 2024-12-11
• DOI: 10.1088/1475-7516/2025/01/028
• EISSN: 1475-7516
• Language: English
• Keywords: gravitational lensing; power spectrum; galaxy clusters