The Completed SDSS-IV extended Baryon Oscillation Spectroscopic Survey: a multi-tracer analysis in Fourier space for measuring the cosmic structure growth and expansion rate

We perform a joint BAO and RSD analysis using the eBOSS DR16 LRG and ELG samples in the redshift range of z ∈ [0.6, 1.1], and detect a RSD signal from the cross power spectrum at a ∼4σ confidence level, i.e., fσ₈ = 0.317 ± 0.080 at z_eff = 0.77. Based on the chained power spectrum, which is a new development in this work to mitigate the angular systematics, we measure the BAO distances and growth rate simultaneously at two effective redshifts, namely, D_M/r_d (z = 0.70) = 17.96 ± 0.51, D_H/r_d (z = 0.70) = 21.22 ± 1.20, fσ₈(z = 0.70) = 0.43 ± 0.05, and D_M/r_d (z = 0.845) = 18.90 ± 0.78, D_H/r_d (z = 0.845) = 20.91 ± 2.86, fσ₈ (z = 0.845) = 0.30 ± 0.08. Combined with BAO measurements including those from the eBOSS DR16 QSO and Lyman-α sample, our measurement has raised the significance level of a nonzero Ω_Λ to ∼11σ. The data product of this work is publicly available at https://github.com/icosmology/eBOSS_DR16_LRGxELG and https://www.sdss.org/science/final-bao-and-rsd-measurements/