The role of LRG1 and LRG2's monopole in inferring the DESI 2024 BAO cosmology

TL;DR

This paper investigates how monopole components of LRG1 and LRG2 influence the divergence of DESI 2024 BAO cosmology results from Planck data, suggesting their monopoles favor thawing dark energy models.

Contribution

It introduces a new analysis focusing on monopole components of LRG1 and LRG2, revealing their significant role in cosmological parameter deviations from Planck results.

Findings

Removing LRG2's $D_V$$ aligns DESI+ CMB+ SNIa with $w=-1$ within 2$\sigma$

Excluding LRG1's $D_V$ shifts $w_0/w_a$ toward $w=-1$

Both LRG1 and LRG2 monopoles favor thawing dark energy, especially LRG2.

Abstract

The Dark Energy Spectroscopic Instrument (DESI) collaboration recently released its first year of data (DR1) on baryon acoustic oscillations (BAO) in galaxy, quasar, and Lyman-$\alpha$ forest tracers. When combined with CMB and SNIa data, DESI BAO results suggest potential thawing behavior in dark energy. Cosmological analyses utilize comoving distances along ($D_H$) and perpendicular to ($D_M$) the line of sight. Notably, there are $1\sim2\sigma$ deviations in $D_M$ and $D_H$ from Planck cosmology values in the luminous red galaxies (LRG) bins LRG1 and LRG2.This study examines the role of LRG1 and LRG2 in diverging DESI 2024 BAO cosmology from Planck cosmology. We use angle-averaged distance $D_V$ and the ratio $F_{\rm AP}=D_M/D_H$, which are more directly related to the measured monopole and quadrupole components of the galaxy power spectrum or correlation function, instead of the officially adopted $D_M$ and $D_H$. This transformation aims to isolate the influence of monopoles in LRG1 and LRG2 on deviations from $w=-1$. Our findings indicate that removing the $D_V$ data point in LRG2 aligns DESI + CMB + SNIa data compilation with $w=-1$ within a $2\sigma$ contour and reduces the $H_0$ discrepancy from the Planck 2018 results from $0.63\sigma$ to $0.31\sigma$. Similarly, excluding the $D_V$ data point from LRG1 shifts the $w_0/w_a$ contour toward $w=-1$, although no intersection occurs. This highlights the preference of both LRG1 and LRG2 BAO monopole components for the thawing dark energy model, with LRG2 showing a stronger preference. We provide the $D_V$ and $F_{\rm AP}$ data and their covariance alongside this paper.