1 research outputs found
Leveraging SN Ia spectroscopic similarity to improve the measurement of
Recent studies suggest spectroscopic differences explain a fraction of the
variation in Type Ia supernova (SN Ia) luminosities after light-curve/color
standardization. In this work, (i) we empirically characterize the variations
of standardized SN Ia luminosities, and (ii) we use a spectroscopically
inferred parameter, SIP, to improve the precision of SNe Ia along the distance
ladder and the determination of the Hubble constant (). First, we show
that the \texttt{Pantheon+} covariance model modestly overestimates the
uncertainty of standardized magnitudes by %, in the parameter space
used by the Team to measure ; accounting for this alone
yields km s Mpc. Furthermore, accounting
for spectroscopic similarity between SNe~Ia on the distance ladder reduces
their relative scatter to mag per object (compared to
mag previously). Combining these two findings in the model of SN covariance, we
find an overall 14% reduction (to km s Mpc) of the
uncertainty in the Hubble constant and a modest increase in its value.
Including a budget for systematic uncertainties itemized by Riess et al.
(2022a), we report an updated local Hubble constant with %
uncertainty, km s Mpc. We conclude that
spectroscopic differences among photometrically standardized SNe Ia do not
explain the ``Hubble tension." Rather, accounting for such differences
increases its significance, as the discrepancy against CDM calibrated
by the 2018 measurement rises to 5.7.Comment: 28 pages, 15 figures, accepted to JCA