By using Fiber Multi-Object Spectrograph (FMOS, Note 1) on the Subaru Telescope, an international team led by Japanese researchers has made a 3D map of 3000 galaxies 13 billion light years from Earth (Figure 1). Based on this comprehensive survey, the first of such a study at this great distance, the team was able to confirm that Einstein's general theory of relativity is still valid.
Since it was discovered in the late 1990s that the universe is expanding at an accelerated rate, scientists have been trying to explain why. The mysterious dark energy could be driving acceleration, or Einstein's theory of general relativity, which says gravity warps space and time, could be breaking down.
To test Einstein's theory, a team of researchers led by Teppei Okumura (Kavli IPMU Project Researcher), Chiaki Hikage (Kavli IPMU Project Assistant Professor), and Tomonori Totani (University of Tokyo Department of Astronomy Professor), used FastSound (Note 2) Survey data on more than 3000 distant galaxies to analyze their velocities and clustering. This survey is one of the strategic observation programs at the Subaru Telescope, and used 40 nights of its telescope time from 2012 to 2014.
Their results indicate that even far into the universe, general relativity is valid, giving further support that the expansion of the universe could be explained by a cosmological constant, as proposed by Einstein in his theory of general relativity.
"We tested the theory of general relativity further than anyone else ever has. It's a privilege to be able to publish our results 100 years after Einstein proposed his theory," said Okumura. "Having started this project 12 years ago it gives me great pleasure to finally see this result come out," said Karl Glazebrook, Professor at Swinburne University of Technology in Australia, who proposed the survey.
No one has been able to analyze galaxies more than 10 billion light years away, but the team managed to break this barrier thanks to the FMOS on the Subaru Telescope, which can analyze galaxies 12.4 to 14.7 billion light years away. The Prime Focus Spectrograph, currently under construction, is expected to be able to study galaxies even further away.
Detail of this study was published in the Publications of the Astronomical Society of Japan on its on-line version of April 26, 2016. The title is " The Subaru FMOS galaxy redshift survey (FastSound). IV. New constraint on gravity theory from redshift space distortions at z~1.4" by Okumura et al. The research was supported by Grant-In-Aid 19740099, 19035005, 20040005, 22012005, 23684007, 26887012, 24740160, 24540286, and 15H05890.
Notes:1.FMOS was constructed as collaboration between the National Astronomical Observatory of Japan (NAOJ), Kyoto University, and the UK Science and Technology Facilities Council (STFC).
2.The name FastSound stands for two important aspects of the project. Fast is short for FMOS Acceleration Sampling Test, which refers to the 3D map from the survey. Sound abbreviates Subaru Observation Understanding Nature of Dark energy, which relates more closely to the scientific purpose of the project, i.e., studying dark energy and its implications for the theory of general relativity.
3.Comoving distance is one of the distance scale used in the cosmology. It is derived from the time that the light spent from the object to reach the observer, including the change caused by the expansion of the universe so far. This press release uses this comoving distance scale.
Paper details:Publications of the Astronomical Society of Japan
Title:The Subaru FMOS galaxy redshift survey (FastSound). IV. New constraint on gravity theory from redshift space distortions at z~1.4
Authors:Teppei Okumura (1), Chiaki Hikage (1), Tomonori Totani (2), Motonari Tonegawa (2), Hiroyuki Okada (2), Karl Glazebrook (3), Chris Blake (3), Pedro G. Ferreira (4), Surhud More (1), Atsushi Taruya (1,5), Shinji Tsujikawa (6), Masayuki Akiyama (7), Gavin Dalton (8,9), Tomotsugu Goto (10), Takashi Ishikawa (11), Fumihide Iwamuro (11), Takahiko Matsubara (12,13), Takahiro Nishimichi (1,14), Kouji Ohta (11), Ikkoh Shimizu (15), Ryuichi Takahashi (16), Naruhisa Takato (17), Naoyuki Tamura (1), Kiyoto Yabe (1), and Naoki Yoshida (1,14,18)
Author affiliations:1.Kavli Institute for the Physics and Mathematics of the Universe (WPI), The University of Tokyo Institutes for Advanced Study, The University of Tokyo, Japann
2.Department of Astronomy, School of Science, The University of Tokyo, Japan
3.Centre for Astrophysics & Supercomputing, Swinburne University of Technology, Australia
4.Department of Physics, University of Oxford, United Kingdom
5.Yukawa Institute for Theoretical Physics, Kyoto University, Japan
6.Department of Physics, Faculty of Science, Tokyo University of Science, Japan
7.Astronomical Institute, Faculty of Science, Tohoku University, Japan
8.Astrophysics, Department of Physics, United Kingdom
9.RALSpace, STFC Rutherford Appleton Laboratory, United Kingdom
10.Institute of Astronomy, National Tsing Hua University, Taiwan
11.Department of Astronomy, Kyoto University Japan
12.Department of Physics, Nagoya University, Japan
13.Kobayashi-Maskawa Institute for the Origin of Particles and the Universe (KMI), Nagoya University, Japan
14.Core Research for Evolutional Science and Technology (CREST), Japan Science and Technology Agency (JST), Japan
15.Department of Earth & Space Science, Graduate School of Science, Osaka University, Japan
16.Faculty of Science and Technology, Hirosaki University, Japan
17.Subaru Telescope, National Astronomical Observatory of Japan, USA
18.Department of Physics, School of Science, The University of Tokyo, Japan