Testing ΛCDM versus Dynamical Dark Energy in 1 Yr: A DESI Spectroscopic Follow-up Program for Rubin Supernovae
Year: 2026
Type: article
Abstract: Combined cosmological probes currently indicate that best-fit values in the w 0 − w a parameterization of dynamical dark energy deviate from ΛCDM by ∼3 σ . In this work, we present a supernova (SN) survey capable of measuring dynamical dark energy at the >5 σ level with just 1 yr of data, starting in 2027. We first show that with the present values of w 0 and w a , new Type Ia supernovae (SNe Ia) at redshifts of z ≲ 0.6 near dark energy-matter equality would add the most constraining power. This is well within reach of the Vera C. Rubin Observatory and the Dark Energy Spectroscopic Instrument (DESI). Because cosmology measurements with SNe Ia quickly become systematics limited, we focus on eliminating key systematics by using only a spectroscopically confirmed and volume-limited sample. In our proposed survey, SN alerts from Rubin would actively reprioritize the scheduling of already-planned DESI tile visits. This would yield 7500 near-peak transient spectra in 1 yr without delaying DESI’s primary survey. We forecast that if current best-fit w 0 − w a values persist, combining just our volume-limited subset of 2300 new SNe Ia at z < 0.3 with current SN, baryon acoustic oscillation, and cosmic microwave background data would push the tension with ΛCDM beyond 5 σ . This applies across a wide range of assumed uncertainties. To further circumvent systematics, we explore how DESI enables spectroscopic standardization via machine learning, offering a path toward a cosmology measurement independent of light-curve-based standardization. Finally, we discuss how early results from this program could inform future dark energy experiments.
Source: The Astrophysical Journal
Language: English
Subfield: Astronomy and Astrophysics
Field: Physics and Astronomy
Domain: Physical Sciences
Open Access status: gold
Estimated APC paid: $4,499
Award: G1105675291
OpenAlex ID: W7214904731