DESI Survey Enhances Understanding of Cosmic Structure Growth

The Dark Energy Spectroscopic Instrument (DESI) Peculiar Velocity Survey has been launched to measure the peculiar velocities of both early and late-type galaxies within the DESI footprint. This survey utilizes the Fundamental Plane and Tully-Fisher relations to achieve its objectives. According to the findings, direct measurements of peculiar velocities can enhance constraints on the growth rate of cosmic structures, potentially reducing uncertainties by a factor of approximately 2.5 at a redshift of 0.1. This improvement is significant when compared to the redshift space distortion measurements from the DESI Bright Galaxy Survey alone.

During the Survey Validation phase, spectra were obtained for 6,698 unique early-type galaxies, reaching up to a photometric redshift of 0.15. Notably, 64% of the observed galaxies exhibited relative velocity dispersion errors below 10%. This percentage rises to 75% when focusing on galaxies with spectroscopic redshifts below 0.1. The survey employed a 3D Gaussian maximum likelihood algorithm to fit the Fundamental Plane parameters, taking into account measurement uncertainties and selection cuts.

Additionally, the survey conducted zero-point calibration using absolute distance measurements to the Coma cluster, resulting in a Hubble constant value of H0 = 76.05 ± 0.35 (statistical) ± 0.49 (systematic FP) ± 4.86 (statistical due to calibration) km/s/Mpc. This value aligns within 2σ of the Planck Cosmic Microwave Background results and within 1σ of other low redshift distance indicator-based measurements. The implications of these findings are crucial for understanding the dynamics of the universe and the behavior of galaxies within it.

For further details, the paper titled "DESI Peculiar Velocity Survey -- Fundamental Plane" can be accessed here.