Galaxy Peculiar Velocities From Large-Scale Supernova Surveys as a Dark Energy Probe

TL;DR

This paper proposes using mean pairwise velocities of supernova host galaxies, derived from upcoming large-scale surveys, as a new and competitive method to probe dark energy, complementing existing techniques.

Contribution

It introduces a novel approach to dark energy measurement using supernova pairwise velocities combined with photometric redshifts, enhancing constraints without extra observational effort.

Findings

Pairwise velocity method is competitive with traditional techniques.

Combining velocities with other data improves dark energy constraints by 1.8 times.

Velocity measurements are less sensitive to redshift systematics.

Abstract

Upcoming imaging surveys such as the Large Synoptic Survey Telescope will repeatedly scan large areas of sky and have the potential to yield million-supernova catalogs. Type Ia supernovae are excellent standard candles and will provide distance measures that suffice to detect mean pairwise velocities of their host galaxies. We show that when combining these distance measures with photometric redshifts for either the supernovae or their host galaxies, the mean pairwise velocities of the host galaxies will provide a dark energy probe which is competitive with other widely discussed methods. Adding information from this test to type Ia supernova photometric luminosity distances from the same experiment, plus the cosmic microwave background power spectrum from the Planck satellite, improves the Dark Energy Task Force Figure of Merit by a factor of 1.8. Pairwise velocity measurements require no additional observational effort beyond that required to perform the traditional supernova luminosity distance test, but may provide complementary constraints on dark energy parameters and the nature of gravity. Incorporating additional spectroscopic redshift follow-up observations could provide important dark energy constraints from pairwise velocities alone. Mean pairwise velocities are much less sensitive to systematic redshift errors than the luminosity distance test or weak lensing techniques, and also are only mildly affected by systematic evolution of supernova luminosity.