Large-scale galaxy correlations from the DESI first data release

¹ Centro Ricerche Enrico Fermi, I-00184 Roma, Italy
² INFN Unità Roma 1, Dipartimento di Fisica, Università di Roma Sapienza, I-00185 Roma, Italy
³ School of Mathematics and the Maxwell Institute for Mathematical Sciences, University of Edinburgh, Edinburgh, United Kingdom

^★ Corresponding author: This email address is being protected from spambots. You need JavaScript enabled to view it.

Received: 26 November 2025
Accepted: 4 February 2026

Abstract

We quantify galaxy correlations using two distinct three-dimensional samples from the first data release of the Dark Energy Spectroscopic Instrument (DESI): the Bright Galaxy Sample (BGS) and the Luminous Red Galaxy Sample (LRGS). Specifically, we measure the conditional average density, defined as the average density of galaxies observed around a typical galaxy in the sample. To minimize boundary effects, we adopt a conservative criterion: the analysis includes only galaxies whose surrounding spherical volume of radius r is fully contained within the survey footprint. For the BGS, we constructed four volume-limited subsamples in order to eliminate biases arising from luminosity-dependent selection effects. In contrast, the LRGS is approximately volume-limited by design. The resulting samples spanned different depths, providing an opportunity to test the stability of statistical measurements across survey volumes of increasing size. Our results show that the conditional average density follows a power-law decay, ⟨n(r)⟩ ∝ r^−0.8, without exhibiting any transition to homogeneity within the survey volume. The large statistics of the DESI samples also allowed us to demonstrate that finite-size effects become significant as r approaches the boundaries of the sample volumes. We consistently found that the distribution of density fluctuations follows a Gumbel distribution – characteristic of extreme-value statistics – rather than a Gaussian distribution, which would be expected for a spatially homogeneous field. These findings confirm and extend the trends previously observed in smaller redshift surveys, supporting the conclusion that the galaxy distribution does not undergo a transition to spatial homogeneity within the probed scales, up to r ∼ 400 Mpc/h.