NASAのウェッブ望遠鏡とハッブル望遠鏡、宇宙の膨張速度を確認、謎は続く(NASA’s Webb, Hubble Telescopes Affirm Universe’s Expansion Rate, Puzzle Persists)

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2024-03-11 NASA

宇宙論の最大の謎の一つである「ハッブル張力」は、現在の宇宙の膨張速度が、宇宙の初期条件と私たちの現在の理解に基づく予想よりも速いことを指摘しています。NASAの宇宙望遠鏡を使用する科学者たちは、ESAのプランクミッションの観測からの予測と一致しない数字を一貫して見つけています。この矛盾を解決するには、新しい物理学が必要なのでしょうか?それとも、宇宙の膨張速度を決定するために使用される2つの異なる方法の間の測定エラーの結果なのでしょうか?

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JWSTの観測により、8σのハッブル張力の説明としてケフェイド測光の未認識の混雑は否定された JWST Observations Reject Unrecognized Crowding of Cepheid Photometry as an Explanation for the Hubble Tension at 8σ Confidence

Adam G. Riess, Gagandeep S. Anand, Wenlong Yuan, Stefano Casertano, Andrew Dolphin, Lucas M. Macri, Louise Breuval, Dan Scolnic, Marshall Perrin, and Richard I. Anderson
The Astrophysical Journal Letters  Published: 2024 February 6
DOI:10.3847/2041-8213/ad1ddd

NASAのウェッブ望遠鏡とハッブル望遠鏡、宇宙の膨張速度を確認、謎は続く(NASA’s Webb, Hubble Telescopes Affirm Universe’s Expansion Rate, Puzzle Persists)

Abstract

We present high-definition observations with the James Webb Space Telescope (JWST) of >1000 Cepheids in a geometric anchor of the distance ladder, NGC 4258, and in five hosts of eight Type Ia supernovae, a far greater sample than previous studies with JWST. These galaxies individually contain the largest samples of Cepheids, an average of >150 each, producing the strongest statistical comparison to those previously measured with the Hubble Space Telescope (HST) in the near-infrared (NIR). They also span the distance range of those used to determine the Hubble constant with HST, allowing us to search for a distance-dependent bias in HST measurements. The superior resolution of JWST negates crowding noise, the largest source of variance in the NIR Cepheid period–luminosity relations (Leavitt laws) measured with HST. Together with the use of two epochs to constrain Cepheid phases and three filters to remove reddening, we reduce the dispersion in the Cepheid PL relations by a factor of 2.5. We find no significant difference in the mean distance measurements determined from HST and JWST, with a formal difference of −0.01 ± 0.03 mag. This result is independent of zero-points and analysis variants including metallicity dependence, local crowding, choice of filters, and slope of the relations. We can reject the hypothesis of unrecognized crowding of Cepheid photometry from HST that grows with distance as the cause of the “Hubble tension” at 8.2σ, i.e., greater confidence than that of the Hubble tension itself. We conclude that errors in photometric measurements of Cepheids across the distance ladder do not significantly contribute to the tension.

1701物理及び化学
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