標準宇宙論モデルの宇宙論パズル

国際的な科学者チームは、Advanced Technologies と Hyper Suprime-Cam を使用して暗黒物質の「塊」を研究し、S8 値 0.76 を発見しました。これは、宇宙マイクロ波背景放射の値 0.83 とは対照的です。 この矛盾は、測定誤差または不完全な標準宇宙論モデルを示している可能性があります。

カブリ数物連携宇宙研究機構 (Kavli IPMU) を含むさまざまな機関の天体物理学者と宇宙学者からなる国際チームは、宇宙に存在する暗黒物質の「塊」の価値を測定する 5 つの研究論文を発表しました。 S のような宇宙論者に。₈、0.76 は、比較的若い宇宙を対象とした他の重力レンズ調査で見つかった値と一致していますが、宇宙マイクロ波背景放射から導き出された値 0.83 とは一致しません。この値は、宇宙の起源を遡ります。宇宙の誕生は約38万年でした。 彼らの結果は、事前に印刷されたシートとしてアップロードされています。 arXiv。

これら 2 つの値の間のギャップは小さいですが、両方の値が確認される研究が増えているため、偶然ではないようです。 おそらく、これら 2 つの測定値のいずれかにこれまで知られていないバグやエラーがあるか、標準的な宇宙論モデルが興味深い点で不完全である可能性があります。

暗黒エネルギーと暗黒物質は、今日私たちが見ている宇宙の 95% を構成していますが、それらが実際に何であるか、また宇宙の歴史の中でどのように進化してきたかについてはほとんどわかっていません。 暗黒物質の塊は、弱い重力レンズによって遠方の銀河の光を歪めますが、これはアインシュタインの一般相対性理論によって予測された現象です。

図 1: HSC-SSP で取得された画像の例。 クレジット: HSC-SSP と国立天文台プロジェクト

「この歪みは非常に小さな影響です。単一の銀河の形状は、知覚できない量で歪みます」とKavli IPMUの高田正裕教授は述べていますが、数百万個の銀河の測定値を組み合わせることで、歪みを高精度で測定できるようになります。

標準モデルは、わずか数個の数値によって定義されます。それは、暗黒物質 (S) の密度の尺度である宇宙の膨張率です。₈）、宇宙の構成要素（物質、暗黒物質、暗黒エネルギー）の相対的な寄与、宇宙全体の密度、および大規模な宇宙の凝集が小規模な宇宙の凝集とどのように関係するかを説明する技術的量。

宇宙学者は、宇宙マイクロ波背景放射の変動の観察、宇宙の膨張履歴のモデル化、比較的最近の宇宙のクラスタリングの測定など、さまざまな方法でこれらの数値を制約することによってこのモデルをテストすることに熱心です。

東京大学カブリ数物連携宇宙研究機構の天文学者が率いるチームは、[{” attribute=””>Nagoya University, Princeton University, and astronomical communities of Japan and Taiwan, have spent the past year teasing out the secrets of this most elusive material, dark matter, using sophisticated computer simulations and data from the first three years of the Hyper Suprime-Cam survey. The observations from this survey used one of the most powerful astronomical cameras in the world, the Hyper Suprime-Cam (HSC) mounted on the Subaru Telescope on the summit of Maunakea in Hawaii.

Figure 2: The measurement results of S8 parameter from HSC-SSP Year 3 data. The chart shows the results from four different methods, which used different parts of the HSC-SSP Year 3 data or combined the HSC-SSP Year 3 data with other data. For comparison, “Planck CMB” shows the measurement result for S8 from the cosmic microwave background data from the Planck satellite. “Other weak lensing results” shows the results from similar weak lensing measurements based on the Dark Energy Survey (DES) and Kilo-Degree Survey (KiDS) data. Credit: Kavli IPMU

Hiding and uncovering the data

The team performed a “blinded analysis.”

“Scientists are human beings, and they do have preferences. Some would love to really find something fundamentally new, while others might feel comfortable if they find results that look consistent with foreseen results. Scientists have become self-aware enough to know that they will bias themselves, no matter how careful they are, unless they carry out their analysis without allowing themselves to know the results until the end,” said Nagoya University Kobayashi-Maskawa Institute for the Origin of Particles and the Universe (KMI) Associate Professor Hironao Miyatake.

To protect the results from such biases, the HSC team hid their results from themselves and their colleagues for months. The team even added an extra obfuscating layer: they ran their analyses on three different galactic catalogs, one real and two fake with numerical values offset by random values. The analysis team didn’t know which of them was real, so even if someone did accidentally see the values, the team wouldn’t know if the results were based on the real catalog or not.

The team spent a year on the blind analysis. On December 3 2022, the team gathered together on Zoom – one Saturday morning in Japan, Friday evening in Princeton – for the “unblinding.” The team unveiled the data, and ran their plots, immediately they saw it was great according to Takada. “Blinded analysis means you cannot take a peak at the results while running the analysis, which was extremely stressful, but as soon I saw the final result, all of that anxiety flew out of the window,” said Kavli IPMU graduate student Sunao Sugiyama.

Figure 3: An example of a 3D distribution of dark matter derived from HSC-SSP. This map is obtained by using the first year’s data, but the present study examined an area on the sky about three times larger than that. Credit: University of Tokyo/NAOJ

A huge survey with the world’s largest telescope camera

HSC is the largest camera on a telescope of its size in the world. The survey that the research team used covers about 420 square degrees of the sky, about the equivalent of 2000 full moons. It is not a single contiguous chunk of sky, but split among six different pieces, each about the size of a person’s outstretched fist. The 25 million galaxies the researchers surveyed are so distant that instead of seeing these galaxies as they are today, the HSC recorded how they were billions of years ago.

Each of these galaxies glows with the fires of tens of billions of suns, but because they are so far away, they are extremely faint, as much as 25 million times fainter than the faintest stars we can see with the naked eye.

For more on this research, see Measuring Dark Matter With Hyper Suprime-Cam Reveals Discrepancy.

References:

“Hyper Suprime-Cam Year 3 Results: Cosmology from Galaxy Clustering and Weak Lensing with HSC and SDSS using the Emulator Based Halo Model” by Hironao Miyatake, Sunao Sugiyama, Masahiro Takada, Takahiro Nishimichi, Xiangchong Li, Masato Shirasaki, Surhud More, Yosuke Kobayashi, Atsushi J. Nishizawa, Markus M. Rau, Tianqing Zhang, Ryuichi Takahashi, Roohi Dalal, Rachel Mandelbaum, Michael A. Strauss, Takashi Hamana, Masamune Oguri, Ken Osato, Wentao Luo, Arun Kannawadi, Bau-Ching Hsieh, Robert Armstrong, Yutaka Komiyama, Robert H. Lupton, Nate B. Lust, Lauren A. MacArthur, Satoshi Miyazaki, Hitoshi Murayama, Yuki Okura, Paul A. Price, Tomomi Sunayama, Philip J. Tait, Masayuki Tanaka and Shiang-Yu Wang, 3 April 2023, Astrophysics > Cosmology and Nongalactic Astrophysics.
arXiv:2304.00704

“Hyper Suprime-Cam Year 3 Results: Measurements of Clustering of SDSS-BOSS Galaxies, Galaxy-Galaxy Lensing and Cosmic Shear” by Surhud More, Sunao Sugiyama, Hironao Miyatake, Markus Michael Rau, Masato Shirasaki, Xiangchong Li, Atsushi J. Nishizawa, Ken Osato, Tianqing Zhang, Masahiro Takada, Takashi Hamana, Ryuichi Takahashi, Roohi Dalal, Rachel Mandelbaum, Michael A. Strauss, Yosuke Kobayashi, Takahiro Nishimichi, Masamune Oguri, Arun Kannawadi, Robert Armstrong, Yutaka Komiyama, Robert H. Lupton, Nate B. Lust, Satoshi Miyazaki, Hitoshi Murayama, Yuki Okura, Paul A. Price, Philip J. Tait, Masayuki Tanaka and Shiang-Yu Wang, 3 April 2023, Astrophysics > Cosmology and Nongalactic Astrophysics.
arXiv:2304.00703

“Hyper Suprime-Cam Year 3 Results: Cosmology from Galaxy Clustering and Weak Lensing with HSC and SDSS using the Minimal Bias Model” by Sunao Sugiyama, Hironao Miyatake, Surhud More, Xiangchong Li, Masato Shirasaki, Masahiro Takada, Yosuke Kobayashi, Ryuichi Takahashi, Takahiro Nishimichi, Atsushi J. Nishizawa, Markus M. Rau, Tianqing Zhang, Roohi Dalal, Rachel Mandelbaum, Michael A. Strauss, Takashi Hamana, Masamune Oguri, Ken Osato, Arun Kannawadi, Robert Armstrong, Yutaka Komiyama, Robert H. Lupton, Nate B. Lust, Satoshi Miyazaki, Hitoshi Murayama, Yuki Okura, Paul A. Price, Philip J. Tait, Masayuki Tanaka and Shiang-Yu Wang, 3 April 2023, Astrophysics > Cosmology and Nongalactic Astrophysics.
arXiv:2304.00705

“Hyper Suprime-Cam Year 3 Results: Cosmology from Cosmic Shear Power Spectra” by Roohi Dalal, Xiangchong Li, Andrina Nicola, Joe Zuntz, Michael A. Strauss, Sunao Sugiyama, Tianqing Zhang, Markus M. Rau, Rachel Mandelbaum, Masahiro Takada, Surhud More, Hironao Miyatake, Arun Kannawadi, Masato Shirasaki, Takanori Taniguchi, Ryuichi Takahashi, Ken Osato, Takashi Hamana, Masamune Oguri, Atsushi J. Nishizawa, Andrés A. Plazas Malagón, Tomomi Sunayama, David Alonso, Anže Slosar, Robert Armstrong, James Bosch, Yutaka Komiyama, Robert H. Lupton, Nate B. Lust, Lauren A. MacArthur, Satoshi Miyazaki, Hitoshi Murayama, Takahiro Nishimichi, Yuki Okura, Paul A. Price, Philip J. Tait, Masayuki Tanaka and Shiang-Yu Wang, 3 April 2023, Astrophysics > Cosmology and Nongalactic Astrophysics.
arXiv:2304.00701

“Hyper Suprime-Cam Year 3 Results: Cosmology from Cosmic Shear Two-point Correlation Functions” by Xiangchong Li, Tianqing Zhang, Sunao Sugiyama, Roohi Dalal, Markus M. Rau, Rachel Mandelbaum, Masahiro Takada, Surhud More, Michael A. Strauss, Hironao Miyatake, Masato Shirasaki, Takashi Hamana, Masamune Oguri, Wentao Luo, Atsushi J. Nishizawa, Ryuichi Takahashi, Andrina Nicola, Ken Osato, Arun Kannawadi, Tomomi Sunayama, Robert Armstrong, Yutaka Komiyama, Robert H. Lupton, Nate B. Lust, Satoshi Miyazaki, Hitoshi Murayama, Takahiro Nishimichi, Yuki Okura, Paul A. Price, Philip J. Tait, Masayuki Tanaka, Shiang-Yu Wang, 3 April 2023, Astrophysics > Cosmology and Nongalactic Astrophysics.
arXiv:2304.00702