The DESI DR1 Peculiar Velocity Survey: global zero-point and $H_0$ constraints

TL;DR

This paper calibrates the DESI DR1 peculiar velocity data to measure the Hubble constant, achieving a precise estimate and exploring systematic uncertainties, with future plans to improve accuracy using additional calibrators.

Contribution

It introduces a calibration of the DESI Fundamental Plane and Tully-Fisher relations for $H_0$ measurement, utilizing a larger sample and alternative calibrators to improve precision.

Findings

Measured $H_0=73.7 ext{ km s}^{-1} ext{ Mpc}^{-1}$ with low statistical uncertainty.

Achieved calibration consistency with supernovae and SBF distances.

Outlined future plans for percent-level $H_0$ measurement using Cepheids and red giant branch stars.

Abstract

The Dark Energy Spectroscopic Instrument (DESI) in its first Data Release (DR1) already provides more than 100,000 galaxies with relative distance measurements. The primary purpose of this paper is to perform the calibration of the zero-point for the DESI Fundamental Plane and Tully-Fisher relations, which allows us to measure the Hubble constant, $H_0$. This sample has a lower statistical uncertainty than any previously used to measure $H_0$, and we investigate the systematic uncertainties in absolute calibration that could limit the accuracy of that measurement. We improve upon the DESI Early Data Release Fundamental Plane $H_0$ measurement by a) using a group catalog to increase the number of calibrator galaxies and b) investigating alternative calibrators in the nearby universe. Our baseline measurement calibrates to the SH0ES/Pantheon+ type Ia supernovae, and finds $H_0=73.7\pm 0.06\;(\text{stat.})\pm 1.1\;(\text{syst.})$ km s$^{-1}$ Mpc$^{-1}$. Calibrating to surface brightness fluctuation (SBF) distances yields a similar $H_0$. We explore measurements using other calibrators, but these are currently less precise since the overlap with DESI peculiar velocity tracers is much smaller. In future data releases with an even larger peculiar velocity sample, we plan to calibrate directly to Cepheids and the tip of the red giant branch, which will enable the uncertainty to decrease towards a percent-level measurement of $H_0$. This will provide an alternative to supernovae as the Hubble flow sample for $H_0$ measurements.