Bayesian hierarchical modeling of ZTF DR2 and Foundation DR1 datasets shows dust explains all low-z SN Ia color variability after correcting for color-cut selection bias, with no residual intrinsic color term needed.
Improved Distances to Type Ia Supernovae with Multicolor Light Curve Shapes: MLCS2k2
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abstract
We present an updated version of the Multicolor Light Curve Shape method to measure distances to type Ia supernovae (SN Ia), incorporating new procedures for K-correction and extinction corrections. We also develop a simple model to disentangle intrinsic color variations and reddening by dust, and expand the method to incorporate U-band light curves and to more easily accommodate prior constraints on any of the model parameters. We apply this method to 133 nearby SN Ia, including 95 objects in the Hubble flow (cz >= 2500 km/s), which give an intrinsic dispersion of less than 7% in distance. The Hubble flow sample, which is of critical importance to all cosmological uses of SN Ia, is the largest ever presented with homogeneous distances. We find the Hubble flow supernovae with Hd >= 7400 km/s yield an expansion rate that is 6.5 +/- 1.8% lower than the rate determined from supernovae within that distance, and this can have a large effect on measurements of the dark energy equation of state with SN Ia. Peculiar velocities of SN Ia host galaxies in the rest frame of the Local Group are consistent with the dipole measured in the Cosmic Microwave Background. Direct fits of SN Ia that are significantly reddened by dust in their host galaxies suggest their mean extinction law may be described by R_V ~= 2.7, but optical colors alone provide weak constraints on R_V.
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DESI-DR2 angular diameter distances and SNeIa luminosity distances are statistically consistent with the Etherington relation, yielding a constraint on SNeIa absolute magnitude evolution of dM/dz = 0.07 ± 0.07.
citing papers explorer
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The colour variability of low-z SNe Ia is entirely explained by dust
Bayesian hierarchical modeling of ZTF DR2 and Foundation DR1 datasets shows dust explains all low-z SN Ia color variability after correcting for color-cut selection bias, with no residual intrinsic color term needed.
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Mapping the Universe as a Bianchi I cosmology with Gaia data
Gaia quasar proper motions show a significant quadrupole signal matching an axisymmetric Bianchi I anisotropy model, but the amplitude does not increase with redshift as the model requires and the inferred local shear exceeds expectations.
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Modeling the probability distribution for cosmological analysis with photometrically classified samples
A simplified likelihood treating photometric contamination as a redshift-dependent Gaussian mean shift is strongly favored by Bayes factor over the BEAMS two-component model and improves cosmological constraints on the DES-Dovekie sample.
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Cosmology-Independent Constraints on the Etherington Relation and SNeIa Absolute Magnitude Evolution from DESI-DR2
DESI-DR2 angular diameter distances and SNeIa luminosity distances are statistically consistent with the Etherington relation, yielding a constraint on SNeIa absolute magnitude evolution of dM/dz = 0.07 ± 0.07.