Fiducial-cosmology-dependent systematics for the DESI 2024 full-shape analysis

DESI Collaboration; N. Findlay; S. Nadathur; E. Gaztañaga

doi:10.1088/1475-7516/2026/06/010

Fiducial-cosmology-dependent systematics for the DESI 2024 full-shape analysis

DESI Collaboration
, N. Findlay
, S. Nadathur
, E. Gaztañaga

Institute of Cosmology & Gravitation

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Abstract

We assess the impact of the fiducial cosmology choice on cosmological inference from full-shape (FS) fits of the galaxy power spectrum in the DESI 2024 Data Release 1 (DR1). Using a suite of AbacusSummit DR1 mock catalogues based on the Planck 2018 best-fit cosmology, we quantify potential systematic shifts introduced by analysing the data under five secondary cosmologies - featuring variations in matter density, thawing dark energy, higher effective number of neutrino species, reduced clustering amplitude, and the DESI DR1 BAO best-fit $w_0w_a$CDM cosmology - relative to DESI's baseline Planck 2018 cosmology. We investigate two complementary FS analysis approaches: full-modelling (FM) and ShapeFit (SF), each with distinct sensitivities to the assumed fiducial model. Across all tracers, we find for FM that systematic shifts induced by fiducial cosmology mismatches remain well below the DESI DR1 statistical uncertainties, with maximum deviations of 0.22$\sigma_\mathrm{DR1}$ in $\Lambda$CDM scenarios and 0.12$\sigma_\mathrm{DR1+SN}$ when including SN Ia mock data in extended $w_0w_a$CDM fits. For SF, the shifts in the compressed parameters remain below $0.45\sigma_\mathrm{DR1}$ for all tracers and cosmologies.

Original language	English
Article number	010
Number of pages	41
Journal	Journal of Cosmology and Astroparticle Physics
Volume	2026
Issue number	06
DOIs	https://doi.org/10.1088/1475-7516/2026/06/010
Publication status	Published - 3 Jun 2026

Keywords

astro-ph.CO
galaxy clustering
power spectrum
dark energy experiments
redshift surveys

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10.1088/1475-7516/2026/06/010

Fiducial-cosmology-dependent systematicsFinal published version, 1.46 MBLicence: CC BY

Cite this

@article{594c03db9697499eb88ffed950c02116,

title = "Fiducial-cosmology-dependent systematics for the DESI 2024 full-shape analysis",

abstract = " We assess the impact of the fiducial cosmology choice on cosmological inference from full-shape (FS) fits of the galaxy power spectrum in the DESI 2024 Data Release 1 (DR1). Using a suite of AbacusSummit DR1 mock catalogues based on the Planck 2018 best-fit cosmology, we quantify potential systematic shifts introduced by analysing the data under five secondary cosmologies - featuring variations in matter density, thawing dark energy, higher effective number of neutrino species, reduced clustering amplitude, and the DESI DR1 BAO best-fit \$w\_0w\_a\$CDM cosmology - relative to DESI's baseline Planck 2018 cosmology. We investigate two complementary FS analysis approaches: full-modelling (FM) and ShapeFit (SF), each with distinct sensitivities to the assumed fiducial model. Across all tracers, we find for FM that systematic shifts induced by fiducial cosmology mismatches remain well below the DESI DR1 statistical uncertainties, with maximum deviations of 0.22\$\textbackslash{}sigma\_\textbackslash{}mathrm\{DR1\}\$ in \$\textbackslash{}Lambda\$CDM scenarios and 0.12\$\textbackslash{}sigma\_\textbackslash{}mathrm\{DR1+SN\}\$ when including SN Ia mock data in extended \$w\_0w\_a\$CDM fits. For SF, the shifts in the compressed parameters remain below \$0.45\textbackslash{}sigma\_\textbackslash{}mathrm\{DR1\}\$ for all tracers and cosmologies. ",

keywords = "astro-ph.CO, galaxy clustering, power spectrum, dark energy experiments, redshift surveys",

author = "\{DESI Collaboration\} and R. Gsponer and S. Ramirez-Solano and F. Rodr{\'i}guez-Mart{\'i}nez and M. Vargas-Maga{\~n}a and S. Novell-Masot and N. Findlay and H. Gil-Mar{\'i}n and P. Zarrouk and S. Nadathur and A. Rocher and S. Brieden and A. P{\'e}rez-Fern{\'a}ndez and J. Aguilar and S. Ahlen and D. Bianchi and D. Brooks and Castander, \{F. J.\} and T. Claybaugh and A. Cuceu and Macorra, \{A. de la\} and \{de Mattia\}, A. and Arjun Dey and P. Doel and A. Font-Ribera and Forero-Romero, \{J. E.\} and E. Gazta{\~n}aga and Gontcho, \{S. Gontcho A\} and G. Gutierrez and J. Guy and C. Hahn and Herrera-Alcantar, \{H. K.\} and K. Honscheid and C. Howlett and D. Huterer and M. Ishak and R. Joyce and R. Kehoe and D. Kirkby and T. Kisner and A. Kremin and O. Lahav and C. Lamman and M. Landriau and Guillou, \{L. Le\} and Levi, \{M. E.\} and C. Magneville and M. Manera and E. Mueller and Percival, \{W. J.\} and L. Samushia",

note = "42 pages, 10 figures, comments are welcome",

year = "2026",

month = jun,

day = "3",

doi = "10.1088/1475-7516/2026/06/010",

language = "English",

volume = "2026",

journal = "Journal of Cosmology and Astroparticle Physics",

issn = "1475-7516",

publisher = "IOP Publishing",

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TY - JOUR

T1 - Fiducial-cosmology-dependent systematics for the DESI 2024 full-shape analysis

AU - DESI Collaboration

AU - Gsponer, R.

AU - Ramirez-Solano, S.

AU - Rodríguez-Martínez, F.

AU - Vargas-Magaña, M.

AU - Novell-Masot, S.

AU - Findlay, N.

AU - Gil-Marín, H.

AU - Zarrouk, P.

AU - Nadathur, S.

AU - Rocher, A.

AU - Brieden, S.

AU - Pérez-Fernández, A.

AU - Aguilar, J.

AU - Ahlen, S.

AU - Bianchi, D.

AU - Brooks, D.

AU - Castander, F. J.

AU - Claybaugh, T.

AU - Cuceu, A.

AU - Macorra, A. de la

AU - de Mattia, A.

AU - Dey, Arjun

AU - Doel, P.

AU - Font-Ribera, A.

AU - Forero-Romero, J. E.

AU - Gaztañaga, E.

AU - Gontcho, S. Gontcho A

AU - Gutierrez, G.

AU - Guy, J.

AU - Hahn, C.

AU - Herrera-Alcantar, H. K.

AU - Honscheid, K.

AU - Howlett, C.

AU - Huterer, D.

AU - Ishak, M.

AU - Joyce, R.

AU - Kehoe, R.

AU - Kirkby, D.

AU - Kisner, T.

AU - Kremin, A.

AU - Lahav, O.

AU - Lamman, C.

AU - Landriau, M.

AU - Guillou, L. Le

AU - Levi, M. E.

AU - Magneville, C.

AU - Manera, M.

AU - Mueller, E.

AU - Percival, W. J.

AU - Samushia, L.

N1 - 42 pages, 10 figures, comments are welcome

PY - 2026/6/3

Y1 - 2026/6/3

N2 - We assess the impact of the fiducial cosmology choice on cosmological inference from full-shape (FS) fits of the galaxy power spectrum in the DESI 2024 Data Release 1 (DR1). Using a suite of AbacusSummit DR1 mock catalogues based on the Planck 2018 best-fit cosmology, we quantify potential systematic shifts introduced by analysing the data under five secondary cosmologies - featuring variations in matter density, thawing dark energy, higher effective number of neutrino species, reduced clustering amplitude, and the DESI DR1 BAO best-fit $w_0w_a$CDM cosmology - relative to DESI's baseline Planck 2018 cosmology. We investigate two complementary FS analysis approaches: full-modelling (FM) and ShapeFit (SF), each with distinct sensitivities to the assumed fiducial model. Across all tracers, we find for FM that systematic shifts induced by fiducial cosmology mismatches remain well below the DESI DR1 statistical uncertainties, with maximum deviations of 0.22$\sigma_\mathrm{DR1}$ in $\Lambda$CDM scenarios and 0.12$\sigma_\mathrm{DR1+SN}$ when including SN Ia mock data in extended $w_0w_a$CDM fits. For SF, the shifts in the compressed parameters remain below $0.45\sigma_\mathrm{DR1}$ for all tracers and cosmologies.

AB - We assess the impact of the fiducial cosmology choice on cosmological inference from full-shape (FS) fits of the galaxy power spectrum in the DESI 2024 Data Release 1 (DR1). Using a suite of AbacusSummit DR1 mock catalogues based on the Planck 2018 best-fit cosmology, we quantify potential systematic shifts introduced by analysing the data under five secondary cosmologies - featuring variations in matter density, thawing dark energy, higher effective number of neutrino species, reduced clustering amplitude, and the DESI DR1 BAO best-fit $w_0w_a$CDM cosmology - relative to DESI's baseline Planck 2018 cosmology. We investigate two complementary FS analysis approaches: full-modelling (FM) and ShapeFit (SF), each with distinct sensitivities to the assumed fiducial model. Across all tracers, we find for FM that systematic shifts induced by fiducial cosmology mismatches remain well below the DESI DR1 statistical uncertainties, with maximum deviations of 0.22$\sigma_\mathrm{DR1}$ in $\Lambda$CDM scenarios and 0.12$\sigma_\mathrm{DR1+SN}$ when including SN Ia mock data in extended $w_0w_a$CDM fits. For SF, the shifts in the compressed parameters remain below $0.45\sigma_\mathrm{DR1}$ for all tracers and cosmologies.

KW - astro-ph.CO

KW - galaxy clustering

KW - power spectrum

KW - dark energy experiments

KW - redshift surveys

U2 - 10.1088/1475-7516/2026/06/010

DO - 10.1088/1475-7516/2026/06/010

M3 - Article

SN - 1475-7516

VL - 2026

JO - Journal of Cosmology and Astroparticle Physics

JF - Journal of Cosmology and Astroparticle Physics

IS - 06

M1 - 010

ER -

Fiducial-cosmology-dependent systematics for the DESI 2024 full-shape analysis

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Keywords

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