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Testing the effect of progenitor's metallicity on $^{56}$Ni mass and constraining the progenitor scenarios in Type Ia supernovae

Young-Lo Kim, Chul Chung, Yong -Cheol Kim

TL;DR

This work tests how the progenitor metallicity $Z_{progenitor}$ shapes $^{56}$Ni synthesis and SN Ia luminosity by leveraging birth-environment abundances $(Fe/H)_{progenitor}$ and $(\alpha/Fe)_{progenitor}$ from $z\sim0$ early-type hosts to compute $Z_{progenitor}$. It estimates $^{56}$Ni masses from light-curve parameters using Arnett's rule and compares them to explosion-model grids from Leung2018, Leung2020, and Gronow2021 to constrain SN Ia progenitor scenarios. The analysis finds a near-zero slope in the $^{56}$Ni mass versus $Z_{progenitor}$ relation within uncertainties, with notable splits in $\alpha$-enhancement that yield a $^{56}$Ni mass difference of $0.12\pm0.04$ $M_\odot$ (3σ). It also shows a modest $0.14\pm0.09$ mag difference in HR between $Z_{progenitor}$ groups, suggesting a tangible progenitor-metallicity effect after standardization and highlighting the value of a holistic, environment-to-explosion approach for SN Ia cosmology. The results motivate larger samples and denser model grids from upcoming surveys to better constrain progenitor channels and mitigate cosmological systematics.

Abstract

The analytical model found that the intrinsic variation in the initial metallicity of the Type Ia supernova (SN Ia) progenitor stars ($Z_{progenitor}$) translates into a 25% variation in the $^{56}$Ni mass synthesized and, therefore, 0.2 mag difference in the observed peak luminosity of SNe Ia. Previous observational studies used the currently-observed global gas-phase metallicity of host galaxies, instead of $Z_{progenitor}$ used in the model, and showed a higher scatter in the $^{56}$Ni mass measurements compared to the model prediction. Here, we use $Z_{progenitor}$ of 34 normal SNe Ia and employ recent SN Ia explosion models with various configurations to cover the observed $^{56}$Ni mass range. Unlike previous studies, our sample covers the $Z_{progenitor}$ range, where most of the $Z_{progenitor}$ effect occurs. Linear regression returns a slope of 0.02+-0.03, which is the opposite trend to the analytical model, but at at low statistical significance level. We find that comparing our sample with SN Ia explosion models on the $Z_{progenitor}$--$^{56}$Ni mass diagram allows us to constrain the progenitor scenarios. We also explore other chemical composition indicators. For $(Fe/H)_{progenitor}$, our sample follows the trend predicted by the analytical models, but at a low significance level. Noticeably, $(α/Fe)_{progenitor}$ shows the opposite trend and a clear gap. When we split the sample at $(α/Fe)_{progenitor}$ = 0.35 $(α/Fe)_{\odot}$, we find a 3$σ$ difference in the weighted-means of the $^{56}$Ni mass. Lastly, SNe Ia in different $Z_{progenitor}$ groups show a difference of 0.14+-0.09 mag in the standardized luminosity. The present work highlights a holistic approach (from the progenitor star to the explosion with SN Ia and host galaxy observational data) to understand the underlying physics of SNe Ia for more accurate and precise cosmology.

Testing the effect of progenitor's metallicity on $^{56}$Ni mass and constraining the progenitor scenarios in Type Ia supernovae

TL;DR

This work tests how the progenitor metallicity shapes Ni synthesis and SN Ia luminosity by leveraging birth-environment abundances and from early-type hosts to compute . It estimates Ni masses from light-curve parameters using Arnett's rule and compares them to explosion-model grids from Leung2018, Leung2020, and Gronow2021 to constrain SN Ia progenitor scenarios. The analysis finds a near-zero slope in the Ni mass versus relation within uncertainties, with notable splits in -enhancement that yield a Ni mass difference of (3σ). It also shows a modest mag difference in HR between groups, suggesting a tangible progenitor-metallicity effect after standardization and highlighting the value of a holistic, environment-to-explosion approach for SN Ia cosmology. The results motivate larger samples and denser model grids from upcoming surveys to better constrain progenitor channels and mitigate cosmological systematics.

Abstract

The analytical model found that the intrinsic variation in the initial metallicity of the Type Ia supernova (SN Ia) progenitor stars () translates into a 25% variation in the Ni mass synthesized and, therefore, 0.2 mag difference in the observed peak luminosity of SNe Ia. Previous observational studies used the currently-observed global gas-phase metallicity of host galaxies, instead of used in the model, and showed a higher scatter in the Ni mass measurements compared to the model prediction. Here, we use of 34 normal SNe Ia and employ recent SN Ia explosion models with various configurations to cover the observed Ni mass range. Unlike previous studies, our sample covers the range, where most of the effect occurs. Linear regression returns a slope of 0.02+-0.03, which is the opposite trend to the analytical model, but at at low statistical significance level. We find that comparing our sample with SN Ia explosion models on the --Ni mass diagram allows us to constrain the progenitor scenarios. We also explore other chemical composition indicators. For , our sample follows the trend predicted by the analytical models, but at a low significance level. Noticeably, shows the opposite trend and a clear gap. When we split the sample at = 0.35 , we find a 3 difference in the weighted-means of the Ni mass. Lastly, SNe Ia in different groups show a difference of 0.14+-0.09 mag in the standardized luminosity. The present work highlights a holistic approach (from the progenitor star to the explosion with SN Ia and host galaxy observational data) to understand the underlying physics of SNe Ia for more accurate and precise cosmology.

Paper Structure

This paper contains 19 sections, 6 equations, 5 figures, 3 tables.

Table of Contents

  1. Introduction
  2. Methodology
  3. Sample
  4. Estimating $Z_{progenitor}$
  5. Estimating $^{56}$Ni mass
  6. Hydrodynamic simulations of SN Ia explosion models
  7. Leung2018
  8. Leung2020
  9. Gronow2021
  10. Result
  11. Constraining SN Ia progenitors on the $Z_{progenitor}$--$^{56}$Ni mass diagram
  12. Timmes2003 and Bravo2010 models
  13. Leung2018 and Leung2020 models
  14. Gronow2021 models
  15. SN Ia progenitors from different models
  16. ...and 4 more sections

Figures (5)

  • Figure 1: $^{56}$Ni mass synthesized during the SN Ia explosion as a function of the progenitor metallicity ($Z_{progenitor}$). Our sample of the 34 normal SNe Ia are indicated with star-shaped orange marks. The analytical Timmes2003 (a black solid curved line) and Bravo2010 linear and non-linear (blue solid and blue dashed lines, respectively) models are overplotted with various SN Ia models investigated in the present work: 3 LN18 near-$M_{ch}$ models (circles with solid lines), 3 LN20 sub-$M_{ch}$ models (squares with dashed lines), and 11 G21 sub-$M_{ch}$ models (diamonds with dash-dotted lines). Our sample is well-distributed across the $Z_{progenitor}$ range where most of the $Z_{progenitor}$ effect occurs, as indicated by notes taken from figure 1 of Timmes2003. The derived $^{56}$Ni masses of our sample are within the $^{56}$Ni mass range expected from various hydrodynamic simulations.
  • Figure 2: Same as Fig. \ref{['fig:nimass_z_all']}, but split the plot by the SN Ia models. The top panel is for Timmes2003 and Bravo2010. A red solid line shows the average of 10,000 linear regression results (light red lines) from the LINMIX package, which returns a slope of $0.02 \pm 0.03$ (0.7$\sigma$). The middle panel is for Leung2018 and Leung2020 models, and the bottom panel is for the Gronow2021 model. In each panel, we mark four SNe Ia, which show a good fit with Leung2018 and Leung2020 models in magenta colour and with the Gronow2021 model in teal colour.
  • Figure 3: $^{56}$Ni mass synthesized during the SN Ia explosion as a function of the progenitor iron abundance ($(Fe/H)_{progenitor}$) and $\alpha$-element enrichment ($(\alpha/Fe)_{progenitor}$). The Timmes2003 model is plotted as a solid black line, even in the expression of $Z_{progenitor}$ / $Z_{\odot}$. Red solid lines show the average of 10,000 linear regression results (light red lines) from the LINMIX package. In the left panel, purple dot-dashed and dotted lines present the Timmes2003 model, altered for thick and thin disk models by Howell2009, respectively. A vertical dashed line in the right panel indicates $(\alpha/Fe)_{progenitor}$ = 0.35, showing a clear gap as discussed in Kim2024. Green squares represent the weighted-means of $^{56}$Ni mass in each $(\alpha/Fe)_{progenitor}$ bin. Our sample seems to favour the Howell2009 thick disk model in terms of the relation between $(Fe/H)_{progenitor}$ and $^{56}$Ni mass, given the $\chi^{2}_{\nu}$ value. The opposite trend to the Timmes2003 model for $(\alpha/Fe)_{progenitor}$ is observed.
  • Figure 4: Impact of $Z_{progenitor}$ on the SN Ia corrected luminosity (i.e. the Hubble residual). Samples with $Z$ of current host galaxies ($Z_{cur,host}$) are also presented with empty star marks. The average of 10,000 linear regression results (light red lines) from the LINMIX package is shown with a red solid line. The LINMIX fit with $Z_{cur,host}$ is indicated with a red dashed line. We split our sample at $Z_{progenitor}$ = 2.5 (the vertical dashed line), where a gap is shown. Green squares are weighted-means of HR in the different $Z_{progenitor}$ group. The trend, although at a low significance level, is opposite to the previous studies using current host galaxy properties.
  • Figure 5: Correlation between $Z_{progenitor}$, $(Fe/H)_{progenitor}$ and $(\alpha/Fe)_{progenitor}$ for our sample. Dashed lines indicate a one-to-one relation.