Forecast for a growth-rate measurement using peculiar velocities from LSST supernovae

¹ Aix Marseille Univ, CNRS/IN2P3, CPPM, Marseille, France
² Department of Physics, Duke University, Durham, NC 27708, USA
³ Université Clermont-Auvergne, CNRS, LPCA, 63000 Clermont-Ferrand, France
⁴ Lawrence Berkeley National Laboratory, 1 Cyclotron Road, Berkeley, CA 94720, USA

^⋆ Corresponding author: rosselli@cppm.in2p3.fr

Received: 30 June 2025
Accepted: 25 July 2025

Abstract

We investigate whether the cosmic growth-rate parameter fσ₈ can be measured using peculiar velocities (PVs) derived from type Ia supernovae (SNe Ia) in the Vera C. Rubin Observatory’s Legacy Survey of Space and Time (LSST). We produced simulations of different SN types using a realistic LSST observing strategy that incorporated noise, a photometric detection from the difference-image analysis (DIA) pipeline, and a PV field modeled from the Uchuu universe machine simulations. We tested three different observational scenarios that ranged from ideal conditions with spectroscopic host galaxy redshifts and spectroscopic SN typing to realistic photometric typing that resulted in a contamination with non-Ia SNe. Using a maximum likelihood technique, we showed that the LSST can measure fσ₈ with a precision of 10% in the redshift range 0.02 < z < 0.14 for our most realistic scenario. In three tomographic bins, the LSST will be able to constrain the growth-rate parameter with errors below 18% up to redshift z = 0.14. We also tested the contamination effect on the maximum likelihood method and found that for a contamination fraction below ∼2%, we recovered unbiased measurements. The results of this analysis highlight that the LSST SN sample is expected to complement traditional redshift-space distortion measurements at high redshift. This will provide a novel avenue for testing general relativity and different dark energy models.