Local non-Gaussianity with DESI (Joint SB/BNL Cosmology Seminar)

by Mehdi Rezaie (Kansas State)

Thursday 30 Nov 2023, 15:00 → 16:00 US/Eastern

small seminar room

Primordial non-Gaussianity (PNG) of the local type generates a primordial bispectrum, which peaks in the squeezed triangle configuration, where one of the modes is on a much larger scale than the other two. The long-wavelength mode couples with the other two to generate a non-Gaussian signal, which affects the local number density of galaxies and induces a scale-dependent feature in the two-point clustering of galaxies and quasars. Probing PNG with this feature is limited by various imaging systematic effects that can modulate the galaxy power spectrum on large scales. For instance, Milky Way extinction can cause excess power which can be misinterpreted as the signature of local PNG. In this talk, I will present a meticulous analysis of local PNG with photometric luminous red galaxies (LRGs) selected from the Dark Energy Spectroscopic Instrument (DESI) Legacy Imaging Surveys. This work takes advantage of a deep learning-based methodology to mitigate systematics and unlock a robust measurement of the galaxy power spectrum on large scales. I will also discuss how lognormal simulations can be employed to assess the significance of remaining systematic error. Our work can be considered as the first attempt to identify major systematics in the DESI LRG targets, so we can be ready for constraining local PNG with DESI spectroscopy.