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

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- forest tracers. When combined with cosmic microwave background (CMB) and Type Ia supernovae (SNIa) data, DESI BAO results suggest potential thawing behaviour in dark energy. Cosmological analyses utilize comoving distances along (D_ H) and perpendicular to (D_ M) the line of sight. Notably, there are 1 2 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 ₀₏=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 contour and reduces the H₀ discrepancy from the Planck 2018 results from 0. 63 to 0. 31. Similarly, excluding the D_ V data point from LRG1 shifts the w₀/wₐ 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 ₀₏ data and their covariance alongside this paper.