Measuring peculiar velocity and tomographic redshift dipole with DESI DR1 catalogs

Yi-Wen Wu, Jun-Qing Xia

First listed 2026-09-01 | Last updated 2026-09-02

Abstract

The so-called ``cosmic dipole tension'' challenges the Cosmological Principle by positing a discrepancy between the Solar System's peculiar velocity inferred from the Cosmic Microwave Background (CMB) dipole and that derived from large-scale structure number-count dipoles. Here we provide a high-precision determination of the kinematic dipole using the redshift-dipole method applied to the first data release (DR1) of the Dark Energy Spectroscopic Instrument (DESI). By exploiting the Doppler-induced modulation of observed redshifts, this estimator is intrinsically less sensitive to imaging systematics and selection-function uncertainties that can bias traditional number-count measurements. We conduct a tomographic analysis of four tracer populations, Bright Galaxy Sample, Luminous Red Galaxies, Emission Line Galaxies, and quasars, spanning $0.1<z<2.1$. Survey geometry and statistical uncertainties are quantified using 1,000 \texttt{EZmock} realizations. We find that the high-redshift QSO sample implies a peculiar velocity of $v = 357.95_{-48.47}^{+55.05}\,\mathrm{km\,s^{-1}}$, in excellent agreement with the CMB-inferred value of $369.82 \pm 0.11\,\mathrm{km\,s^{-1}}$. By contrast, a complementary number-count analysis yields a significantly enhanced dipole amplitude, which we attribute to leakage of large-scale power and to incompleteness within the DESI DR1 footprint. These results indicate that the redshift dipole provides a cleaner and more reliable probe of the kinematic rest frame, offering strong support for the standard kinematic interpretation at high redshift and helping to resolve the apparent dipole anomaly.

Short digest

Wu and Xia use the DESI DR1 redshift-dipole estimator to measure the Solar System’s peculiar velocity tomographically with BGS, LRG, ELG, and QSO samples spanning 0.1<z<2.1. The high-redshift QSO catalog yields v=357.95^{+55.05}_{-48.47} km s^-1, consistent with the CMB-dipole value of 369.82±0.11 km s^-1, supporting a standard kinematic origin for the dipole on the largest DESI scales. In contrast, conventional number counts give an enhanced dipole that the authors associate with large-scale-power leakage and incomplete DESI footprint coverage, positioning redshift dipoles as the cleaner rest-frame diagnostic.

Key figures to inspect

• Figure 1. This Mollweide map establishes the four DESI DR1 tracer footprints and marks the CMB-dipole direction in the QSO panel. It is essential context for the paper’s central methodological claim, because the substantial sky incompleteness and resulting survey window are the proposed explanation for the inflated number-count dipole relative to the redshift-dipole result.