A revised SALT2 surface for fitting Type Ia supernova light curves

Taylor, Georgie; Lidman, C.; Tucker, B. E.; Brout, D.; Hinton, S. R.; Keßler, R.

doi:10.1093/mnras/stab962

Cited by 22 publications

(24 citation statements)

References 66 publications

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“…Throughout this work, we have repeatedly encountered a number of the steps of the analysis that have a large impact on various downstream codependent products of the analysis: new calibration (or MWEBV Maps/Color law) motivates new SALT2 training, which motivates new fitting of the SN parent populations, which motivates new bias corrections. The Pippin framework (Hinton & Brout 2020), used extensively in this work, was intentionally developed to automate and asynchronize this multistep type of analysis; however, it has yet to incorporate aspects such as the SALT2 retraining (Taylor et al 2021) or population fitting (Popovic et al 2021a). Likely, this framework will need to expand for future analyses.…”

Section: Discussionmentioning

confidence: 99%

“…1. Baseline: We use the Fragilistic calibration solution and newly trained SALT2 model ("SALT2-B22") which was developed following the formalism of Guy et al (2010) and Taylor et al (2021). Systematics: For each of the 9 correlated realizations of Fragilistic zero-points discussed above (for Calibration) we simultaneously retrain the SALT2 model.…”

Section: Salt2 Modelmentioning

confidence: 99%

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The Pantheon+ Analysis: Cosmological Constraints

Brout¹,

Scolnic²,

Popovic³

et al. 2022

Preprint

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We present constraints on cosmological parameters from the Pantheon+ analysis of 1701 light curves of 1550 distinct Type Ia supernovae (SNe Ia) ranging in redshift from z = 0.001 to 2.26. This work features an increased sample size, increased redshift span, and improved treatment of systematic uncertainties in comparison to the original Pantheon analysis and results in a factor of 2 improvement in cosmological constraining power. For a FlatΛCDM model, we find Ω M = 0.338 ± 0.018 from SNe Ia alone. For a Flatw 0 CDM model, we measure w 0 = −0.89 ± 0.13 from SNe Ia alone, H 0 = 72.86 +0.94 −1.06 km s −1 Mpc −1 when including the Cepheid host distances and covariance (SH0ES), and w 0 = −0.978 +0.024 −0.031 when combining the SN likelihood with constraints from the cosmic microwave background (CMB) and baryon acoustic oscillations (BAO); both w 0 values are consistent with a cosmological constant. We also present the most precise measurements to date on the evolution of dark energy in a Flatw 0 w a CDM universe, and measure w a = −0.4 +1.0 −1.8 from Pantheon+ alone, H 0 = 73.40 +0.99 −1.22 km s −1 Mpc −1 when including SH0ES, and w a = −0.65 +0.28 −0.32 when combining Pan-theon+ with CMB and BAO data. Finally, we find that systematic uncertainties in the use of SNe Ia along the distance ladder comprise less than one third of the total uncertainty in the measurement of H 0 and cannot explain the present "Hubble tension" between local measurements and early-Universe predictions from the cosmological model.

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Section: Discussionmentioning

confidence: 99%

Section: Salt2 Modelmentioning

confidence: 99%

The Pantheon+ Analysis: Cosmological Constraints

Brout¹,

Scolnic²,

Popovic³

et al. 2022

Preprint

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“…The Spectral Adaptive Light Curve Template-2 (SALT2; Guy et al 2007) is an improvement on the original SALT algorithm and has been recently revised (e.g. Taylor et al 2021).…”

Section: Supernova Light Curvesmentioning

confidence: 99%

Connecting Infrared Surface Brightness Fluctuation Distances to Type Ia Supernova Hosts: Testing the Top Rung of the Distance Ladder

Garnavich¹,

Wood²,

Milne³

et al. 2022

Preprint

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We compare infrared surface brightness fluctuation (IR SBF) distances measured in galaxies that have hosted type Ia supernovae (SNe Ia) to distances estimated from SNe Ia light curve fits. We show that the properties of SNe Ia found in IR-SBF hosts are very different from those exploding in Cepheid calibrators, therefore, this is a direct test of systematic uncertainties on estimation of the Hubble-Lemaître constant (H 0 ) using supernovae. The IR SBF results from Jensen et al. ( 2021) provide a large and uniformly measured sample of IR SBF distances which we directly compare with distances to 25 SNe Ia host galaxies. We divide the Hubble flow SNe Ia into sub-samples that best match the divergent supernova properties seen in the IR SBF hosts and Cepheid hosts. We further divide the SNe Ia into a sample with light curve widths and host masses that are congruent to those found in the SBF-calibrated hosts. We refit the light curve stretch and color correlations with luminosity, and use these revised parameters to calibrate the Hubble flow SNe Ia with IR SBF calibrators. Relative to the Hubble flow, the average calibrator distance moduli vary by 0.03 mag depending on the SNe Ia subsamples examined and this adds a 1.8% systematic uncertainty to our Hubble-Lemaître constant estimate. Based on the IR SBF calibrators, H 0 = 74.6 ± 0.9(stat)±2.7(syst) km s −1 Mpc −1 , which is consistent with the Hubble-Lemaître constant derived from SNe Ia calibrated from Cepheid variables. We conclude that IR SBF provides reliable calibration of SNe Ia with a precision comparable to Cepheid calibrators, and with a significant saving in telescope time.

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“…For cosmological analyses with the SN Ia light-curve fitter SALT2 (Guy et al 2007(Guy et al , 2010, highly-reddened SN Ia are cut (−0.3 < 𝑐 < 0.3 with 𝑐 ∼ 𝐸 (𝐵 − 𝑉) − 0.1, e.g., Betoule et al 2014;Scolnic et al 2018;Brout et al 2022). These SNe Ia are not used in the training of the spectral model itself (Betoule et al 2014;Taylor et al 2021;Brout et al 2021), but it has not been shown that they cannot be used. In this analysis, we investigate these highly-reddened SNe Ia to constrain the evolution and variability of reddening.…”

Section: Introductionmentioning

confidence: 99%

Constraining R$_V$ Variation Using Highly Reddened Type Ia Supernovae from the Pantheon+ Sample

Rose¹,

Popovic²,

Scolnic³

et al. 2022

Preprint

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Type Ia supernovae (SNe Ia) are powerful tools for measuring the expansion history of the universe, but the impact of dust around SNe Ia remains unknown and is a critical systematic uncertainty. One way to improve our empirical description of dust is to analyse highly reddened SNe Ia (𝐸 (𝐵 − 𝑉) > 0.4, roughly equivalent to the fitted SALT2 light-curve parameter 𝑐 > 0.3). With the recently released Pantheon+ sample, there are 57 SNe Ia that were removed because of their high colour alone (with colours up to 𝑐 = 1.61), which can provide enormous leverage on understanding line-of-sight 𝑅 𝑉 . Previous studies have claimed that 𝑅 𝑉 decreases with colour, though it is unclear if this is due to limited statistics, selection effects, or an alternative explanation. To test this claim, we fit two separate colour-luminosity relationships, one for the main cosmological sample (𝑐 < 0.3) and one for highly reddened (𝑐 > 0.3) SNe Ia. We find the change in the colour-luminosity coefficient to be consistent with zero. Additionally, we compare the data to simulations with different colour models, and find that the data prefers a model with a flat dependence of 𝑅 𝑉 on colour over a declining dependence. Finally, our results strongly support that line-of-sight 𝑅 𝑉 to SNe Ia is not a single value, but forms a distribution.

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A revised SALT2 surface for fitting Type Ia supernova light curves

Cited by 22 publications

References 66 publications

The Pantheon+ Analysis: Cosmological Constraints

The Pantheon+ Analysis: Cosmological Constraints

Connecting Infrared Surface Brightness Fluctuation Distances to Type Ia Supernova Hosts: Testing the Top Rung of the Distance Ladder

Constraining R$_V$ Variation Using Highly Reddened Type Ia Supernovae from the Pantheon+ Sample

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