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Some problems associated with the standardization of the light curve of type 1a supernovae

A. P. Mahtessian, G. S. Karapetian, H. F. Khachatryan, M. A. Hovhannisyan, L. A. Mahtessian, L. E. Byzalov, J. M. Sarkissian

TL;DR

The paper investigates whether standardizing Type Ia supernova luminosities with SALT2 and SiFTO yields redshift-dependent biases. It analyzes multiple SN Ia samples and demonstrates a strong redshift dependence of the standardization parameters, particularly through the relation $\Delta M=\alpha X1-\beta C$, with slopes around $0.18$ to $0.26$ per unit redshift and high statistical significance. An absolute magnitude test shows that after standardization the inferred absolute magnitude $M$ correlates with redshift, whereas removing standardization or allowing an evolution term $\epsilon z$ can alter the cosmological inferences, including cases with $\epsilon=0.177$ or $\epsilon=0.361$ leading to different $\Omega_\Lambda$ and $\Omega_M$ values. These results imply that standardization may introduce large systematics in SN Ia distance measurements and thus challenge the interpretation of cosmic acceleration as solely due to dark energy.

Abstract

We show that the parameters used to standardize the luminosity of Type 1a supernovae in the SALT2 and SiFTO models are strongly dependent on the redshift z. Consequently, when standardized with increasing z, the average absolute magnitudes of Type 1a supernovae are artificially increased. This means that for a given apparent magnitude they are, on average, assigned larger distances than they actually are, creating the appearance of their recession with acceleration and requiring the introduction of the concept of antigravity (dark energy) to explain it. We also show that after standardization, Type 1a supernovae cease to be standard candles. We therefore argue that such a standardization is not suitable for measuring the distances to Type 1a supernovae, and hence the accelerating expansion of the Universe is called into question.

Some problems associated with the standardization of the light curve of type 1a supernovae

TL;DR

The paper investigates whether standardizing Type Ia supernova luminosities with SALT2 and SiFTO yields redshift-dependent biases. It analyzes multiple SN Ia samples and demonstrates a strong redshift dependence of the standardization parameters, particularly through the relation , with slopes around to per unit redshift and high statistical significance. An absolute magnitude test shows that after standardization the inferred absolute magnitude correlates with redshift, whereas removing standardization or allowing an evolution term can alter the cosmological inferences, including cases with or leading to different and values. These results imply that standardization may introduce large systematics in SN Ia distance measurements and thus challenge the interpretation of cosmic acceleration as solely due to dark energy.

Abstract

We show that the parameters used to standardize the luminosity of Type 1a supernovae in the SALT2 and SiFTO models are strongly dependent on the redshift z. Consequently, when standardized with increasing z, the average absolute magnitudes of Type 1a supernovae are artificially increased. This means that for a given apparent magnitude they are, on average, assigned larger distances than they actually are, creating the appearance of their recession with acceleration and requiring the introduction of the concept of antigravity (dark energy) to explain it. We also show that after standardization, Type 1a supernovae cease to be standard candles. We therefore argue that such a standardization is not suitable for measuring the distances to Type 1a supernovae, and hence the accelerating expansion of the Universe is called into question.
Paper Structure (5 sections, 14 equations, 5 figures)

This paper contains 5 sections, 14 equations, 5 figures.

Table of Contents

  1. Introduction
  2. Results
  3. Dependence of standardization parameters on redshift
  4. Absolute magnitude test: Do Type 1a supernovae remain distance standards after standardization?
  5. Conclusion

Figures (5)

  • Figure 1: Dependencies of the values of $\Delta{M}$, introduced to standardize the luminosities of type 1a supernovae, on the redshift.
  • Figure 2: Dependence of the absolute magnitude ${M}$ on the redshift, for the sample of Betoule2014, for the cosmological parameters $\Omega_\Lambda=0.705, \Omega_M=0.295$.
  • Figure 3: Dependence of the absolute magnitude ${M}$ on the redshift, for the sample of Betoule2014, for the cosmological parameters $\Omega_\Lambda=0.505, \Omega_M=0.495$.
  • Figure 4: Dependence of the absolute magnitude ${M}$ on the redshift, for the sample of Betoule2014, for the best fit parameters $\epsilon=0.177; \alpha=0.117, \beta=2.437, \Omega_\Lambda=0.547,\Omega_M=0.453$ (Case C).
  • Figure 5: Dependence of the absolute magnitude ${M}$ on the redshift, for the sample of Betoule2014, for the best fit parameters $\epsilon=0.361; \Omega_\Lambda=0.058,\Omega_M=0.942$ (Case D).