Peculiar-velocity cosmology with Types Ia and II supernovae

Abstract

We present the Democratic Samples of Supernovae (DSS), a compilation of 775 low-redshift Type Ia and II supernovae (SNe Ia & II), of which 137 SN Ia distances are derived via the newly developed snapshot distance method. Using the objects in the DSS as tracers of the peculiar-velocity field, we compare against the corresponding reconstruction from the 2M++ galaxy redshift survey. Our analysis — which takes special care to properly weight each DSS subcatalogue and cross-calibrate the relative distance scales between them — results in a measurement of the cosmological parameter combination $f\sigma _8 = 0.390_{-0.022}^{+0.022}$ as well as an external bulk flow velocity of $195_{-23}^{+22}$ km s−1 in the direction $(\ell , b) = (292_{-7}^{+7}, -6_{-4}^{+5})$ deg, which originates from beyond the 2M++ reconstruction. Similarly, we find a bulk flow of $245_{-31}^{+32}$ km s−1 toward $(\ell , b) = (294_{-7}^{+7}, 3_{-5}^{+6})$ deg on a scale of ∼30 h−1 Mpc if we ignore the reconstructed peculiar-velocity field altogether. Our constraint on fσ8 — the tightest derived from SNe to date (considering only statistical error bars), and the only one to utilise SNe II — is broadly consistent with other results from the literature. We intend for our data accumulation and treatment techniques to become the prototype for future studies that will exploit the unprecedented data volume from upcoming wide-field surveys.

The Pantheon+ Analysis: Cosmological Constraints

“…As discussed by Scolnic et al (2019), the constraining power of large samples of SNe Ia extends beyond inferences of H 0 and w/Ω M . Large compilations of low-z SNe Ia enable precision measurements of the local growth-of-structure, typically parameterized by f σ 8 (e.g., Huterer et al 2017;Stahl et al 2021). Work is ongoing for this measurement using the Pantheon+ sample (Boruah et al, in prep.…”

Cosmology Intertwined: A Review of the Particle Physics, Astrophysics, and Cosmology Associated with the Cosmological Tensions and Anomalies

“…These are described in Ref. [1836] and include measurements of σ 8 from peculiar velocities at low-z [1837] and from the impact of lensing at high-z [1838] and further measurements of H 0 from lensed SNe Ia [1839].…”

Observational constraints on the deceleration parameter in a tilted universe

“…(2.13), as well as the use of different types of cosmological data. Those from the Pantheon+ dataset [15], the SnIa compilation on [103], or from SnIa and from Sn of type II [104], should help to constrain further the parameters of the tilted model.…”