Supernovae Unite: Host-Galaxy Mass Measurements of Type Ia Supernovae and Their Impact on Cosmology

@misc{lee2026supernovae,
  title = {{Supernovae Unite: Host-Galaxy Mass Measurements of Type Ia Supernovae and Their Impact on Cosmology}},
  author = {J Lee and R Camilleri and T.M Davis and D Rubin and K Bechtol and L Galbany and M Sako and M Sullivan and T.E Müller-Bravo and D Scolnic and M Vincenzi and D Brout and C Lidman and A Möller and P Shah and M Acevedo and P Armstrong and B.A Bassett and R.C Chen and H.T Diehl and J Frieman and K Grech and B Popovic and B.O Sánchez and B.E Tucker},
  howpublished = {HAL},
  year = {2026},
  month = sep,
  doi = {10.48550/arxiv.2609.05321},
  eprint = {2609.05321},
  archivePrefix = {arXiv},
  url = {https://hal.science/hal-05759146v1},
  note = {CC BY 4.0},
}

TY  - UNPB
TI  - Supernovae Unite: Host-Galaxy Mass Measurements of Type Ia Supernovae and Their Impact on Cosmology
AU  - J Lee
AU  - R Camilleri
AU  - T.M Davis
AU  - D Rubin
AU  - K Bechtol
AU  - L Galbany
AU  - M Sako
AU  - M Sullivan
AU  - T.E Müller-Bravo
AU  - D Scolnic
AU  - M Vincenzi
AU  - D Brout
AU  - C Lidman
AU  - A Möller
AU  - P Shah
AU  - M Acevedo
AU  - P Armstrong
AU  - B.A Bassett
AU  - R.C Chen
AU  - H.T Diehl
AU  - J Frieman
AU  - K Grech
AU  - B Popovic
AU  - B.O Sánchez
AU  - B.E Tucker
PY  - 2026
DA  - 2026/09/09
PB  - HAL
DO  - 10.48550/arxiv.2609.05321
UR  - https://hal.science/hal-05759146v1
AB  - Current consensus suggests that Type Ia supernova (SN Ia) brightnesses post light-curve standardization correlate with their host-galaxy stellar masses, which must be accounted for to obtain accurate cosmological constraints. For example, Vincenzi et al. (2025) showed that different host-galaxy stellar mass measurements for the same dataset produce redshift-dependent differences of order ∼ 0.01 mag, large enough to appreciably shift cosmological constraints. We present internally consistent host-galaxy stellar masses remeasured using aperture photometry and spectral energy distribution (SED) fitting for SN-Unite, which combines the spectroscopic Pantheon+ and the photometric Dark Energy Survey five-year (DES-SN5YR) samples into the largest SN Ia cosmology sample to date, with 2884 likely SNe Ia. We find that photometry and SED fitting choices shift SN-Unite FlatwCDM parameters well below statistical uncertainties. Our stellar masses differ from the Pantheon+ data release partly due to a redshift-dependent internal inconsistency within Pantheon+, while remaining largely consistent with the DES-SN5YR (DES-Dovekie) data release. When the Pantheon+ subsample of SN-Unite is combined with Baryon Acoustic Oscillations (BAO) and Cosmic Microwave Background (CMB) measurements, the significance for time-evolving dark energy increases from 3.4σ to 4.0σ based on the maximum a posteriori when our newly derived host-galaxy stellar masses replace the Pantheon+ data-release host-galaxy stellar masses, while DES-Dovekie remains virtually unchanged, consistent with the findings of Hoyt et al. (2026). By remeasuring the host-galaxy stellar masses using a consistent framework throughout the whole sample, we improve the robustness of the SN-Unite cosmological constraints against systematic differences in host-galaxy stellar mass measurements.
ER  -