Impact of LRG1 and LRG2 in DESI 2024 BAO data on dark energy evolution

Recent measurements of baryon acoustic oscillations (BAO) by the Dark Energy Spectroscopic Instrument (DESI) suggest a preference for a dynamic dark energy model over a cosmological constant. This conclusion emerges from the combination of DESI's BAO data with observations of the Cosmic Microwave Background (CMB) and various type Ia supernova (SN Ia) catalogues. The deviation observed in the cosmological constant () reflects a departure from the standard cosmological model. Testing this deviation involves examining the consistency between cosmological parameters derived from early and late-time observations. Specifically, we focus on the matter density parameter ₘ = ₘh² and introduce ratio (ₘ) to assess consistency, which is defined as the ratio of ₘ values constrained by high and low-redshift measurements. This ratio serves as a metric for quantifying deviations from the CDM model. In this paper, we find that the DESI BAO+CMB yields ratio (ₘ) =1. 01710. 0066. Upon excluding the LRG1 and LRG2 data in DESI BAO, this ratio adjusts to ratio (ₘ) =1. 01000. 0082. This shift, corresponding to a change from 2. 6 to 1. 2, indicates that the deviation from the CDM model is predominantly driven by these two samples from the DESI BAO measurements. To substantiate this conclusion, we utilized two cosmological model-independent methods to reconstruct the cosmic expansion history. Both reconstructions of the Hubble parameter H (z) indicate that the evolving features of dark energy are determined by the combined LRG1 and LRG2 data. Therefore, different methods have reached the same conclusion, namely the importance of accurately measuring the BAO feature in LRG1 and LRG2 data.