Constraining primordial non-Gaussianity from DESI quasar targets and Planck CMB lensing

Journal Article · 12 March 2024 · Journal of Cosmology and Astroparticle Physics

DOI: https://doi.org/10.1088/1475-7516/2024/03/021 · OSTI ID:2352618

Krolewski, Alex ^[1]; Percival, Will J.; Ferraro, Simone; Chaussidon, Edmond; Rezaie, Mehdi; Aguilar, Jessica Nicole; Ahlen, Steven; Brooks, David; Dawson, Kyle; de la Macorra, Axel; Doel, Peter; Fanning, Kevin; Font-Ribera, Andreu; a Gontcho, Satya Gontcho; Guy, Julien; Honscheid, Klaus; Kehoe, Robert; Kisner, Theodore; Kremin, Anthony; Landriau, Martin ; Levi, Michael E.; Martini, Paul; Meisner, Aaron M.; Miquel, Ramon; Nie, Jundan; Poppett, Claire; Ross, Ashley J.; Rossi, Graziano; Schubnell, Michael; Seo, Hee-Jong; Tarlé, Gregory; Vargas-Magaña, Mariana; Weaver, Benjamin Alan; Yèche, Christophe; Zhou, Rongpu; Zhou, Zhimin

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1. University of Michigan, Ann Arbor MI

We detect the cross-correlation between 2.7 million DESI quasar targets across 14,700 deg² (180 quasars deg^-2) and Planck 2018 CMB lensing at ~30σ. We use the cross-correlation on very large scales to constrain local primordial non-Gaussianity via the scale dependence of quasar bias. The DESI quasar targets lie at an effective redshift of 1.51 and are separated into four imaging regions of varying depth and image quality. We select quasar targets from Legacy Survey DR9 imaging, apply additional flux and photometric redshift cuts to improve the purity and reduce the fraction of unclassified redshifts, and use early DESI spectroscopy of 194,000 quasar targets to determine their redshift distribution and stellar contamination fraction (2.6%). Due to significant excess large-scale power in the quasar autocorrelation, we apply weights to mitigate contamination from imaging systematics such as depth, extinction, and stellar density. We use realistic contaminated mocks to determine the greatest number of systematic modes that we can fit, before we are biased by overfitting and spuriously remove real power. We find that linear regression with one to seven imaging templates removed per region accurately recovers the input cross-power, f_NL and linear bias. As in previous analyses, our fNL constraint depends on the linear primordial non-Gaussianity bias parameter, b_Φ = 2(b - p)δ_c assuming universality of the halo mass function. We measure f_NL = -26⁺⁴⁵_-40 with p = 1.6 (f_NL = -18⁺²⁹_-27 with p = 1.0), and find that this result is robust under several systematics tests. Future spectroscopic quasar cross-correlations with Planck lensing can tighten the f_NL constraints by a factor of 2 if they can remove the excess power on large scales in the quasar auto power spectrum.

• Research Organization: University of Michigan, Ann Arbor, MI (United States)
• Sponsoring Organization: USDOE Office of Science (SC); USDOE Office of Science (SC), Basic Energy Sciences (BES). Scientific User Facilities (SUF)
• Contributing Organization: DESI collaboration; Planck collaboration
• Grant/Contract Number: AC02-05CH11231; SC0019193
• OSTI ID: 2352618
• Journal Information: Journal of Cosmology and Astroparticle Physics, Journal Name: Journal of Cosmology and Astroparticle Physics Journal Issue: 03 Vol. 2024; ISSN 1475-7516
• Publisher: Institute of Physics (IOP)Copyright Statement
• Country of Publication: United States
• Language: English