Cosmic flows in the nearby Universe: new peculiar velocities from SNe and cosmological constraints

TL;DR

This study uses a new sample of 465 low-redshift Type Ia supernovae to map peculiar velocities, compare them with galaxy redshift data, and derive cosmological parameters like $f\sigma_8$, providing insights into dark matter distribution and large-scale flows.

Contribution

It introduces a combined analysis of supernovae and galaxy redshift data to accurately infer peculiar velocities and cosmological parameters at low redshift.

Findings

Inferred bulk flow outside survey volume: 171 km/s.

Measured $f\sigma_8$ = 0.400 ± 0.017.

Residual bulk flow consistent with previous results.

Abstract

The peculiar velocity field offers a unique way to probe dark matter density field on large scales at low redshifts. In this work, we have compiled a new sample of 465 peculiar velocities from low redshift $(z < 0.067)$ Type Ia supernovae. We compare the reconstructed velocity field derived from the 2M++ galaxy redshift compilation to the supernovae, the SFI++ and the 2MTF Tully-Fisher distance catalogues. We used a forward method to jointly infer the distances and the velocities of distance indicators by comparing the observations to the reconstruction. Comparison of the reconstructed peculiar velocity fields to observations allows us to infer the cosmological parameter combination $f\sigma_8$, and the bulk flow velocity arising from outside the survey volume. The residual bulk flow arising from outside the 2M++ volume is inferred to be $171^{+11}_{-11}$ km s$^{-1}$ in the direction $l=301^{\circ} \pm 4^{\circ}$ and $b=0^{\circ} \pm 3^{\circ}$. We obtain $f\sigma_{8} = 0.400 \pm 0.017$, equivalent to $S_8 \approx \sigma_8(\Omega_m/0.3)^{0.55}=0.776\pm0.033$, which corresponds to an approximately $ 4\%\,$ statistical uncertainty on the value of $f\sigma_8$. Our inferred value is consistent with other low redshift results in the literature.