Strong dependence of Type Ia supernova standardization on the local specific star formation rate

Abstract

As part of an ongoing effort to identify, understand and correct for astrophysics biases in the standardization of Type Ia supernovae (SN Ia) for cosmology, we have statistically classified a large sample of nearby SNe Ia into those located in predominantly younger or older environments. This classification is based on the specific star formation rate measured within a projected distance of 1 kpc from each SN location, (LsSFR). This is an important refinement compared to using the local star formation rate directly (Rigault et al. 2013; 2015), as it provides a normalization for relative numbers of available SN progenitors and is more robust against extinction by dust. We find that the SNe Ia in predominantly younger environments are ∆ Y = 0.163 ± 0.029 mag (5.7 σ) fainter than those in predominantly older environments after conventional light-curve standardization. This is the strongest standardized SN Ia brightness systematic connected to host-galaxy environment measured to date. The well-established step in standardized brightnesses between SNe Ia in hosts with lower or higher total stellar masses is smaller, at ∆ M = 0.119 ± 0.032 mag (4.5 σ), for the same set of SNe Ia. When fit simultaneously, the environment age offset remains very significant, with ∆ Y = 0.129 ± 0.032 mag (4.0 σ), while the global stellar mass step is reduced to ∆ M = 0.064 ± 0.029 mag (2.2 σ). Thus, approximately 70% of the variance from the stellar mass step is due to an underlying dependence on environment-based progenitor age. Also, we verify that using the local star formation rate alone is not as powerful as LsSFR at sorting SNe Ia into brighter and fainter subsets. Standardization using only the SNe Ia in younger environments reduces the total dispersion from 0.142 ± 0.008 mag to 0.120 ± 0.010 mag. We show that as environment ages evolve with redshift, a strong bias, especially on measurement of the derivative of the dark energy equation of state, can develop. Fortunately, data to measure and correct for this effect using our local specific star formation rate indicator is likely to be available for many next-generation SN Ia cosmology experiments.

Redshift evolution of the underlying type Ia supernova stretch distribution

“…This in turn raises the question of the accuracy of such corrections because the global properties of the host galaxies evolve with redshift. More recently, studies have used the local SN host galaxy environment to probe more direct connections between the SNe and their host galaxy environments (Rigault et al 2013), showing that local age tracers such as the local specific star formation rate (LsSFR) or the local color are more strongly correlated with the standardized SN magnitude (Roman et al 2018;Kim et al 2018;Rigault et al 2020). The identification of SN Ia spectral features that are correlated with LsSFR (Nordin et al 2018) further support this connection.…”

Resolving the Hubble tension with new early dark energy

“…where ½ _ H AE is specified in (69b). 18 In summary, all perturbations (except for NEDE perturbations) are continuous, while their first derivatives, in general, are not. In particular, the discontinuity of _ η and _ h is set by the spatial variations of the transition surface δq à ¼ δqðt à ; kÞ.…”

“…In Refs. [18,19], the Cepheid calibration of the SH0ES Collaboration was criticized; however, these corrections have been argued not to be sufficient to resolve the tension in later work [20,21]. In the meanwhile, the Cepheid discussion in the observational community continues with vigor [22][23][24].…”

“…To be precise, the 17 It is straightforward to relax this assumption, but it does not add any useful freedom to the calculation. 18 The remaining two constants are then fixed as usual by requiring adiabatic superhorizon perturbations in the metric to scale as h ¼ Ck 2 τ 2 (with τ the conformal time and C constant) when fixing initial conditions during radiation domination (see, for example, [60]). discontinuity of (76) together with ( 82), (69b), and ( 84) results in our main result of this section:…”

Toward Cosmicflows-4: The HI data catalog

“…The cuts were later modified in order to obtain more distant galaxies: δ > 38 deg, 3000 < cz < 10 000 km s −1 , and 40 < i < 85 deg. Lastly, a few SNIa hosts from SNfactory (Rigault et al 2020;Aldering et al 2002) with a redshift up to 12 000 km s −1 were added to the list of targets.…”