ZTF SN~Ia DR2: Cosmology-independent constraints on Type Ia supernova standardisation from supernova siblings

Abstract

Understanding Type Ia supernovae (SNe~Ia) and the empirical standardisation relations that make them excellent distance indicators is vital to improving cosmological constraints. SN~Ia ``siblings", i.e. two or more SNe~Ia in the same host or parent galaxy offer a unique way to infer the standardisation relations and their diversity across the population. We analyse a sample of 25 SN~Ia pairs, observed homogeneously by the Zwicky Transient Factory (ZTF) to infer the SNe~Ia light curve width-luminosity and colour-luminosity parameters $\alpha$ and $\beta$. Using the pairwise constraints from siblings, allowing for a diversity in the standardisation relations, we find $\alpha =0.218\pm 0.055$ and $\beta =3.084\pm 0.312$, respectively, with a dispersion in $\alpha$ and $\beta$ of $\le 0.195$ and $\le 0.923$, respectively, at 95$\%$ C.L. While the median dispersion is large, the values within $\sim 1\sigma$ are consistent with no dispersion. Hence, fitting for a single global standardisation relation, we find $\alpha =0.228\pm 0.029$ and $\beta =3.160\pm 0.191$. We find a very small intrinsic scatter of the siblings sample ${\sigma }_{\mathrm{int}}\le 0.10$ at 95\% C.L. compared to ${\sigma }_{\mathrm{int}}=0.22\pm 0.04$ when computing the scatter using the Hubble residuals without comparing them as siblings. Splitting the sample based on host galaxy stellar mass, we find that SNe~Ia in both subsamples have consistent $\alpha$ and $\beta$. The $\beta$ value is consistent with the value for the cosmological sample. However, we find a higher $\alpha$ by $\sim 2.5-3.5\sigma$. The high $\alpha$ is driven by low $x_1$ pairs, potentially suggesting that the slow and fast declining SN~Ia have different slopes of the width-luminosity relation. We can confirm or refute this with increased statistics from near future time-domain surveys. (abridged)

12 pages, 7 figures, submitted to A&A

References in corpus (19)

• A Comprehensive Measurement of the Local Value of the Hubble Constant with 1 km/s/Mpc Uncertainty from the Hubble Space Telescope and the SH0ES Team
• The Zwicky Transient Facility: System Overview, Performance, and First Results
• The Zwicky Transient Facility: Data Processing, Products, and Archive
• The Pantheon+ Analysis: The Full Dataset and Light-Curve Release
• The Zwicky Transient Facility: Science Objectives
• The Zwicky Transient Facility: Observing System
• The Carnegie Supernova Project: Intrinsic Colors of Type Ia Supernovae
• The Pantheon+ Analysis: SuperCal-Fragilistic Cross Calibration, Retrained SALT2 Light Curve Model, and Calibration Systematic Uncertainty
• A Fully Automated Integral Field Spectrograph Pipeline for the SEDMachine: pysedm
• The colour-lightcurve shape relation of Type Ia supernovae and the reddening law
• A data science platform to enable time-domain astronomy
• Testing the Consistency of Dust Laws in SN Ia Host Galaxies: A BayeSN Examination of Foundation DR1
• Near-IR Type Ia SN distances: host galaxy extinction and mass-step corrections revisited
• A Revised SALT2 Surface for Fitting Type Ia Supernova Light Curves
• Accuracy of environmental tracers and consequence for determining the Type Ia Supernovae magnitude step
• SN 2013aa and SN 2017cbv: Two Sibling Type Ia Supernovae in the spiral galaxy NGC 5643
• Further evidence that galaxy age drives observed type Ia supernova luminosity differences
• ZTF SN Ia DR2: Environmental dependencies of stretch and luminosity of a volume limited sample of 1,000 Type Ia Supernovae
• Supernova Siblings and their Parent Galaxies in the Zwicky Transient Facility Bright Transient Surve

Cited by in corpus (1)

• CIGaRS I: Combined simulation-based inference from type Ia supernovae and host photometry