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#hubbleconstant

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Public
Daniel Fischer

The Complete Sample of Available SNe Ia Luminosity Calibrations from the TRGB Observed with either HST or JWST: arxiv.org/abs/2504.08921 (spoiler: the 'local' #HubbleConstant is really 72 to 73 km/s/Mpc) -> thread x.com/DScol/status/19121849238

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arXiv.orgThe Complete Sample of Available SNe Ia Luminosity Calibrations from the TRGB Observed with either HST or JWSTDistance ladders which calibrate the luminosity of Type Ia supernovae (SNe Ia) currently provide the strongest constraints on the local value of H0. Recent studies from the Hubble Space Telescope (HST) and James Webb Space Telescope (JWST) show good consistency between measurements of SNe Ia host distances. These are calibrated to NGC 4258 using different primary distance indicators (Cepheids, Tip of the Red Giant Branch (TRGB), J-region Asymptotic Giant Branch, and Miras). However, some sub-samples of calibrated SNe Ia employed to measure H0 yield noteworthy differences due to small sample statistics but also due to differences in sample selection. This issue is particularly important for TRGB-derived calibrations owing to the smaller volume they reach compared to Cepheids, reducing sample size and enhancing the size of statistical fluctuations. To mitigate this issue, we compile the largest and complete (as currently available) sample of HST or JWST measurements of the TRGB in the hosts of normal SNe Ia for a total of N=35, 50% larger than the previous largest. Most are present in the literature, and we compile multiple measures when available. We also add 5 SNe Ia hosts from the HST archive not previously published. The full sample together with the Pantheon+ SN catalog gives H0=72.1-73.3 +/- 1.8 km/s/Mpc (depending on methodology), in good agreement with the value of 72.5 +/- 1.5 km/s/Mpc from HST Cepheids in hosts of 42 SNe Ia calibrated by the same anchor, NGC 4258. We trace the difference in the result of H0=70.4 +/- 1.9 km/s/Mpc from Freedman et al. 2025 to 11 hosts not selected for that CCHP compilation (of N=24) which alone yield H0=74.1 km/s/Mpc, 2$σ$ higher than the selected sample. A smaller increase of 0.6 km/s/Mpc comes from a commonly employed correction for peculiar velocities.
Public
Benjamin Carr, Ph.D. 👨🏻‍💻🧬

Turning the #Hubble tension into a crisis: New measurement confirms #universe is expanding too fast for current models
The universe is expanding faster than predicted by theoretical models, and faster than can be explained by our current understanding of #physics.
They arrived at a value for the #HubbleConstant of 76.5 kilometers per second per megaparsec which matches existing measurements, but not as our current understanding of physics predicts it.
phys.org/news/2025-01-hubble-t

Phys.org · Turning the Hubble tension into a crisis: New measurement confirms universe is expanding too fast for current modelsBy Marie Claire Chelini
Public
Daniel Fischer

JWST Validates HST Distance Measurements - Selection of Supernova Subsample Explains Differences in JWST Estimates of Local H0: iopscience.iop.org/article/10. -> Webb telescope's largest study of universe expansion confirms challenge to cosmic theory: hub.jhu.edu/2024/12/09/webb-te - the findings offer a crucial cross-check for previous Hubble Space Telescope measurements of the universe's mysterious expansion. #HubbleConstant

iopscience.iop.orgRadware Bot Manager Captcha
Public
Daniel Fischer

Status Report on the Chicago-Carnegie Hubble Program (CCHP) - Three Independent Astrophysical Determinations of the #HubbleConstant Using the James Webb Space Telescope: arxiv.org/abs/2408.06153 -> Space telescope data reignite debate over how fast universe is expanding—and whether ‘new physics’ is needed: science.org/content/article/sp - triple measurement of the Hubble constant using JWST suggests unidentified biases may account for disparate results.

arXiv.orgStatus Report on the Chicago-Carnegie Hubble Program (CCHP): Three Independent Astrophysical Determinations of the Hubble Constant Using the James Webb Space TelescopeWe present the latest results from the Chicago Carnegie Hubble Program (CCHP) to measure the Hubble constant using data from the James Webb Space Telescope (JWST). This program is based upon three independent methods: (1) Tip of the Red Giant Branch (TRGB) stars, (2) JAGB (J-Region Asymptotic Giant Branch) stars, and (3) Cepheids. Our program includes 10 nearby galaxies, each hosting Type Ia supernovae, suitable for measuring the Hubble constant (Ho). It also includes NGC 4258, which has a geometric distance, setting the zero point for all three methods. The JWST observations have significantly higher signal-to-noise and finer angular resolution than previous observations with the Hubble Space Telescope (HST). We find three independent values of Ho = 69.85 +/- 1.75 (stat) +/- 1.54 (sys) for the TRGB, Ho = 67.96 +/- 1.85 (stat) +/- 1.90 (sys) for the JAGB, and Ho = 72.05 +/- 1.86 (stat) +/- 3.10 (sys) km/s/Mpc for Cepheids. Tying into supernovae, and combining these methods adopting a flat prior, yields our current estimate of Ho = 69.96 +/- 1.05 (stat) +/- 1.12 (sys) km/s/Mpc. The distances measured using the TRGB and the JAGB method agree at the 1% level, but differ from the Cepheid distances at the 2.5-4% level. The value of Ho based on these two methods with JWST data alone is Ho = 69.03 +/- 1.75 (total error) km/sec/Mpc. These numbers are consistent with the current standard Lambda CDM model, without the need for the inclusion of additional new physics. Future JWST data will be required to increase the precision and accuracy of the local distance scale.
Public *
In the Dark

Back in April I posted about a meeting at the Royal Society in London called Challenging the Standard Cosmological Model, some of which I attended virtually. In that post I mentioned that Wendy Freedman gave a talk related to the ongoing issue of the Hubble Tension, i.e. the discrepancy between different types of measurement of the Hubble Constant, usually characterized as local measurements (using stellar distance indicators) and larger-scale measurements (chiefly Planck). There are quite a few posts about this issue on this blog. Anyway, Wendy Freedman mention in her talk that her latest work on stellar distances suggested a value of 69.1 ± km s-1 Mpc-1, which reduces the tension with Planck significantly. At the time, however, there was no paper explaining how this number was derived.

Yesterday there appeared on arXiv a preprint by Freedman et al. which summarizes the recent results. The abstract is here:

We present the latest results from the Chicago Carnegie Hubble Program ( CCHP) to measure the Hubble constant using data from the James Webb Space Telescope (JWST). This program is based upon three independent methods: (1) Tip of the Red Giant Branch (TRGB) stars, (2) JAGB (J-Region Asymptotic Giant Branch) stars, and (3) Cepheids. Our program includes 10 nearby galaxies, each hosting Type Ia supernovae (SNe Ia), suitable for measuring the Hubble constant (H0). It also includes NGC  4258, which has a geometric distance, setting the zero point for all three methods. The JWST observations have significantly higher signal-to-noise and finer angular resolution than previous observations with the Hubble Space Telescope (HST). We find three independent values of H0 = 69.85 ± 1.75 (stat) ± 1.54 (sys) for the TRGB, H0 = 67.96 ± 1.85 (stat) ± 1.90 (sys)  km s-1 Mpc-1 for the JAGB, and H0 = 72.05 ± 1.86 (stat) ± 3.10 (sys) for Cepheids. Tying into SNe Ia, and combining these methods adopting a flat prior, yields our current estimate of H0 = 69.96 ± 1.05 (stat) ± 1.12 (sys)  km s-1 Mpc-1. The distances measured using the TRGB and the JAGB method agree at the 1% level, but differ from the Cepheid distances at the 2.5-4% level. The value of H0 based on these two methods with JWST data alone is H0 = 69.03 ± 1.75 (total error)  km s-1 Mpc-1. These numbers are consistent with the current standard ΛCDM model, without the need for the inclusion of additional new physics. Future JWST data will be required to increase the precision and accuracy of the local distance scale.

You can read the full paper on arXiv here. A summary of the summary is that of the three methods they use, two give lower values of the Hubble constant and one (Cepheids) gives a higher value but with larger errors. The number quoted in the Royal Society talk was presumably preliminary as it doesn’t match any of the numbers in the abstract, but the point remains.

You can see the reduction in scatter in the new JWST measurements in this Figure (old on the left and new on the right).

On the face of it, these results suggest that the Hubble tension is greatly reduced. I am sure, however, that advocates of a higher value will have been preparing their ripostes and it’s just a matter of time before they arrive on the arXiv too!

https://telescoper.blog/2024/08/14/hubble-tension-reduced/

#arXiv240806153#HubbleConstant#HubbleTension
Public
Daniel Pomarède

World’s top cosmologists convene to question conventional view of the universe

Meeting at London’s Royal Society will scrutinise basic model first formulated in 1922 that universe is a vast, even expanse with no notable features.

theguardian.com/science/2024/a

The Guardian · World’s top cosmologists convene to question conventional view of the universeBy Hannah Devlin
#cosmology#conference#London
Public
Daniel Pomarède

Improving the foundation of the cosmic distance ladder and reinforcing the possibility of physics beyond ΛCDM:

Small Magellanic Cloud Cepheids Observed with HST Provide a New Anchor for the SH0ES Distance Ladder
by Louise Breuval and co-authors
arxiv.org/abs/2404.08038

arXiv.orgSmall Magellanic Cloud Cepheids Observed with the Hubble Space Telescope Provide a New Anchor for the SH0ES Distance LadderWe present photometric measurements of 88 Cepheid variables in the core of the Small Magellanic Cloud (SMC), the first sample obtained with the Hubble Space Telescope (HST) and Wide Field Camera 3, in the same homogeneous photometric system as past measurements of all Cepheids on the SH0ES distance ladder. We limit the sample to the inner core and model the geometry to reduce errors in prior studies due to the non-trivial depth of this Cloud. Without crowding present in ground-based studies, we obtain an unprecedentedly low dispersion of 0.102 mag for a Period-Luminosity relation in the SMC, approaching the width of the Cepheid instability strip. The new geometric distance to 15 late-type detached eclipsing binaries in the SMC offers a rare opportunity to improve the foundation of the distance ladder, increasing the number of calibrating galaxies from three to four. With the SMC as the only anchor, we find H$_0\!=\!74.1 \pm 2.1$ km s$^{-1}$ Mpc$^{-1}$. Combining these four geometric distances with our HST photometry of SMC Cepheids, we obtain H$_0\!=\!73.17 \pm 0.86$ km s$^{-1}$ Mpc$^{-1}$. By including the SMC in the distance ladder, we also double the range where the metallicity ([Fe/H]) dependence of the Cepheid Period-Luminosity relation can be calibrated, and we find $γ= -0.22 \pm 0.05$ mag dex$^{-1}$. Our local measurement of H$_0$ based on Cepheids and Type Ia supernovae shows a 5.8$σ$ tension with the value inferred from the CMB assuming a $Λ$CDM cosmology, reinforcing the possibility of physics beyond $Λ$CDM.
#cosmology#HubbleConstant#HubbleTension
Public
Benjamin Carr, Ph.D. 👨🏻‍💻🧬

Study: #Astronomers have made new measurements of the #HubbleConstant, a measure of how quickly the #Universe is expanding, by combining data from the #Hubble #Space #Telescope and the #JamesWebbSpaceTelescope. Conflicting values for the Hubble Constant are NOT due to measurement error
Something else is influencing the expansion rate of the Universe, value differs by about 10 percent! arstechnica.com/science/2024/0

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