천체물리학자와 우주론자로 구성된 국제 팀이 우주 암흑 물질의 “뭉침”(S8 값)이 0.76임을 나타내는 5개의 논문을 제출했습니다. .
국제 과학자 팀은 Advanced Technologies와 Hyper Supreme-Cam을 사용하여 암흑 물질 ‘덩어리’를 연구하여 S8 값 0.76을 찾았습니다. 이는 우주 배경 마이크로파의 값 0.83과 대조됩니다. 이러한 불일치는 측정 오류 또는 불완전한 표준 우주론 모델을 나타낼 수 있습니다.
Kavli IPMU(Kavli IPMU)를 비롯한 다양한 기관의 천체물리학자 및 우주론자로 구성된 국제 팀이 우주에 있는 암흑 물질 “덩어리”의 가치를 측정하는 5개의 연구 논문 세트를 발표했습니다. S.8, 0.76은 상대적으로 젊은 우주를 관찰하는 다른 중력 렌즈 조사에서 발견된 값과 일치하지만 우주 마이크로파 배경에서 파생된 0.83 값과는 일치하지 않습니다. 우주의 나이는 약 380,000년이었습니다. 그들의 결과는 미리 인쇄된 시트로 에 업로드되었습니다. arXiv.
이 두 값의 차이는 적지만, 점점 더 많은 연구가 두 값을 확인함에 따라 우연한 것으로 보이지 않습니다. 이 두 가지 측정 중 하나에 지금까지 알려지지 않은 버그나 오류가 있거나 표준 우주론 모델이 흥미로운 방식으로 불완전할 가능성이 있습니다.
암흑 에너지와 암흑 물질은 오늘날 우리가 보는 우주의 95%를 차지하지만, 그들이 실제로 무엇이며 우주의 역사에서 어떻게 진화했는지에 대해서는 거의 이해하지 못하고 있습니다. 암흑 물질 덩어리는 아인슈타인의 일반 상대성 이론에서 예측한 현상인 약한 중력 렌즈 현상을 통해 먼 은하의 빛을 왜곡합니다.
그림 1: HSC-SSP로 얻은 이미지의 예. 크레딧: HSC-SSP 및 NAOJ 프로젝트
Kavli IPMU Masahiro Takada 교수는 “이 왜곡은 정말 작은 효과입니다. 단일 은하의 모양은 눈에 띄지 않는 양으로 왜곡되지만 수백만 개의 은하 측정을 결합하면 왜곡을 매우 정밀하게 측정할 수 있습니다.
표준 모델은 몇 가지 숫자로 정의됩니다. 즉, 암흑 물질의 밀도(S8), 우주 구성 요소(물질, 암흑 물질 및 암흑 에너지)의 상대적 기여도, 우주의 전체 밀도, 대규모 우주 덩어리가 소규모 우주 덩어리와 어떻게 관련되는지 설명하는 기술적 양.
우주론자들은 우주 마이크로파 배경의 요동을 관찰하거나 우주의 팽창 역사를 모델링하거나 비교적 최근 과거의 우주 클러스터링을 측정하는 등 다양한 방식으로 이러한 수치를 제한함으로써 이 모델을 시험하기를 열망하고 있습니다.
도쿄 대학 Kavli IPMU의 천문학자들이 이끄는 팀,[{” 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
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