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ABSTRACT The local distance ladder estimate of the Hubble constant (H0) is important in cosmology, given the recent tension with the early universe inference. We estimate H0 from the Type Ia supernova (SN Ia) distance ladder, inferring SN Ia distances with the hierarchical Bayesian SED model, BayeSN. This method has a notable advantage of being able to continuously model the optical and near-infrared (NIR) SN Ia light curves simultaneously. We use two independent distance indicators, Cepheids or the tip of the red giant branch (TRGB), to calibrate a Hubble-flow sample of 67 SNe Ia with optical and NIR data. We estimate H0 = 74.82 ± 0.97 (stat) $$\pm \, 0.84$$ (sys) km $${\rm s}^{-1}\, {\rm Mpc}^{-1}$$ when using the calibration with Cepheid distances to 37 host galaxies of 41 SNe Ia, and 70.92 ± 1.14 (stat) $$\pm \, 1.49$$ (sys) km $${\rm s}^{-1}\, {\rm Mpc}^{-1}$$ when using the calibration with TRGB distances to 15 host galaxies of 18 SNe Ia. For both methods, we find a low intrinsic scatter σint ≲ 0.1 mag. We test various selection criteria and do not find significant shifts in the estimate of H0. Simultaneous modelling of the optical and NIR yields up to ∼15 per cent reduction in H0 uncertainty compared to the equivalent optical-only cases. With improvements expected in other rungs of the distance ladder, leveraging joint optical-NIR SN Ia data can be critical to reducing the H0 error budget.
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Analysing the large-scale bulk flow using cosmicflows4: increasing tension with the standard cosmological model
ABSTRACT We present an estimate of the bulk flow in a volume of radii 150−200 h−1 Mpc using the minimum variance method with data from the CosmicFlows-4 (CF4) catalogue. The addition of new data in the CF4 has resulted in an increase in the estimate of the bulk flow in a sphere of radius 150 h−1 Mpc relative to the CosmicFlows-3 (CF3). This bulk flow has an $$\sim 0.015~{{\ \rm per\ cent}}$$ chance of occurring in the standard cosmological model with cosmic microwave background derived parameters. Given that the CF4 is deeper than the CF3, we were able to use the CF4 to accurately estimate the bulk flow on scales of 200 h−1 Mpc (equivalent to 266 Mpc for Hubble constant H0 = 75 km s−1 Mpc−1) for the first time. This bulk flow is in even greater tension with the standard model, having $$\sim 1.5\times 10^{-4}\ \%$$ probability of occurring. To estimate the bulk flow accurately, we introduce a novel method to calculate distances and velocities from distance moduli that is unbiased and accurate at all distances. Our results are completely independent of the value of H0.
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- PAR ID:
- 10431583
- Publisher / Repository:
- Oxford University Press
- Date Published:
- Journal Name:
- Monthly Notices of the Royal Astronomical Society
- Volume:
- 524
- Issue:
- 2
- ISSN:
- 0035-8711
- Format(s):
- Medium: X Size: p. 1885-1892
- Size(s):
- p. 1885-1892
- Sponsoring Org:
- National Science Foundation
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