Kavli Affiliate: Risa Wechsler
| First 5 Authors: Khaled Said, Cullan Howlett, Tamara Davis, John Lucey, Christoph Saulder
| Summary:
The Dark Energy Spectroscopic Instrument (DESI) Peculiar Velocity Survey aims
to measure the peculiar velocities of early and late type galaxies within the
DESI footprint using both the Fundamental Plane and Tully-Fisher relations.
Direct measurements of peculiar velocities can significantly improve
constraints on the growth rate of structure, reducing uncertainty by a factor
of approximately 2.5 at redshift 0.1 compared to the DESI Bright Galaxy
Survey’s redshift space distortion measurements alone. We assess the quality of
stellar velocity dispersion measurements from DESI spectroscopic data. These
measurements, along with photometric data from the Legacy Survey, establish the
Fundamental Plane relation and determine distances and peculiar velocities of
early-type galaxies. During Survey Validation, we obtain spectra for 6698
unique early-type galaxies, up to a photometric redshift of 0.15. 64% of
observed galaxies (4267) have relative velocity dispersion errors below 10%.
This percentage increases to 75% if we restrict our sample to galaxies with
spectroscopic redshifts below 0.1. We use the measured central velocity
dispersion, along with photometry from the DESI Legacy Imaging Surveys, to fit
the Fundamental Plane parameters using a 3D Gaussian maximum likelihood
algorithm that accounts for measurement uncertainties and selection cuts. In
addition, we conduct zero-point calibration using the absolute distance
measurements to the Coma cluster, leading to a value of the Hubble constant,
$H_0 = 76.05 pm 0.35$(statistical) $pm 0.49$(systematic FP) $pm
4.86$(statistical due to calibration) $mathrm{km s^{-1} Mpc^{-1}}$. This
$H_0$ value is within $2sigma$ of Planck Cosmic Microwave Background results
and within $1sigma$, of other low redshift distance indicator-based
measurements.
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