2023/02/17 by Barreira, Alexandre, Krause, Elisabeth · 2 citations
#Cosmology and Nongalactic Astrophysics (astro-ph.CO) #FOS: Physical sciences
paper · doi:10.48550/arxiv.2302.09066
We discuss the potential of the multi-tracer technique to improve observational constraints of the local primordial non-Gaussianity (PNG) parameter f\rm NL from the galaxy power spectrum. For two galaxy samples A and B, the constraining power is ∝ |b1B bϕA - b1AbϕB|, where b1 and bϕ are the linear and PNG galaxy bias parameters. We show this allows for significantly improved constraints compared to the traditional expectation ∝ |b1A - b1B| based on naive universality-like relations where bϕ∝ b1. Using IllustrisTNG galaxy simulation data, we find that different equal galaxy number splits of the full sample lead to different |b1B bϕA - b1AbϕB|, and thus have different constraining power. Of all of the strategies explored, splitting by g-r color is the most promising, more than doubling the significance of detecting f\rm NLbϕ≠ 0. Importantly, since these are constraints on f\rm NLbϕ and not f\rm NL, they do not require priors on the bϕ(b1) relation. For direct constraints on f\rm NL, we show that multi-tracer constraints can be significantly more robust than single-tracer to bϕ misspecifications and uncertainties; this relaxes the precision and accuracy requirements for bϕ priors. Our results present new opportunities to improve our chances to detect and robustly constrain f\rm NL, and strongly motivate galaxy formation simulation campaigns to calibrate the bϕ(b1) relation.