Using host galaxy spectroscopy to explore systematics in the standardization of Type Ia supernovae

Abstract

We use stacked spectra of the host galaxies of photometrically identified type Ia supernovae (SNe Ia) from the Dark Energy Survey (DES) to search for correlations between Hubble diagram residuals and the spectral properties of the host galaxies. Utilising full spectrum fitting techniques on stacked spectra binned by Hubble residual, we find no evidence for trends between Hubble residuals and properties of the host galaxies that rely on spectral absorption features (<1.3σ), such as stellar population age, metallicity, and mass-to-light ratio. However, we find significant trends between the Hubble residuals and the strengths of [OII] (4.4σ) and the Balmer emission lines (3σ). These trends are weaker than the well known trend between Hubble residuals and host galaxy stellar mass (7.2σ) that is derived from broad band photometry. After light curve corrections, we see fainter SNe Ia residing in galaxies with larger line strengths. We also find a trend (3σ) between Hubble residual and the Balmer decrement (a measure of reddening by dust) using Hβ and Hγ. The trend, quantified by correlation coefficients, is slightly more significant in the redder SNe Ia, suggesting that bluer SNe Ia are relatively unaffected by dust in the interstellar medium of the host and that dust contributes to current Hubble diagram scatter impacting the measurement of cosmological parameters.

Asymmetry between Galaxy Apparent Magnitudes Shows a Possible Tension between Physical Properties of Galaxies and Their Rotational Velocity

“…Because the rotational velocity of a galaxy correlates with the galaxy type, the link between rotational velocity and H o can be related to previous reports on the correlation between H o and the type of the Ia supernova host galaxy [115]. Other studies also suggested a link between the Ia supernova and the properties of its host galaxies [116,117].…”

Doppler Shift Effect as a Possible Explanation to the Hubble-Lemaitre Constant Tension

“…Further experiments with more data will be required to test whether the rotational velocity of the host galaxies affect the H o . A possible link between the type and properties of host galaxies and the H o has been noted (Khetan et al, 2021;Meldorf et al, 2022;Dixon et al, 2022). These links can be explained by the correlation between the galaxy properties and its rotational velocity.…”

Environmental Dependence of Type Ia Supernovae in Low-redshift Galaxy Clusters

“…This in turn means that SN Ia environments are linked to their standardization, and may impact their use as cosmological probes, because host galaxy properties vary with redshift. For instance, this could introduce a bias to the dark energy equation of state parameter, w, of around its current statistical uncertainty of ∼4% (Rigault et al 2020;Brout & Scolnic 2021;Brout et al 2022;Dixon et al 2022). The relationship between environment and SN Ia light curve properties also has important implications for progenitor and explosion models.…”