The 3D position and shape information for each galaxy helped to measure the magnitude of the alignment relative to distant galaxies. Credit: KyotoU/Jake Tobiyama
Scientists have confirmed that the intrinsic alignments of galaxies can probe dark matter and dark energy on a cosmological scale, supporting general relativity on a broad spatial scale. However, the nature of dark energy and cosmic acceleration remains unresolved.
Einstein would nod in agreement. General relativity can be applied even to the most distant parts of the universe.
Now, scientists from international research institutions, including Kyoto University, have confirmed that the intrinsic alignments of galaxies have properties that allow it to be a powerful probe of dark matter and dark energy in a cosmological scale.
By gathering evidence that the distribution of galaxies more than tens of millions of light years away is subject to the gravitational effect of dark matter, the team succeeded in testing the general theory of gravity on a large spatial scale. The international team analyzed the positions and orientations of galaxies, obtained from archived data of 1.2 million space observations. With the help of the available 3D positional information of each galaxy, the resulting statistical analysis quantitatively characterized the extent to which the orientations of distant galaxies are aligned.
“These alignments, which are mainly produced by interactions with nearby objects, are considered systematic noise in the measurement of the weak lensing effect,” said lead author Atsushi Taruya of the Yukawa Institute for Theoretical Physics of KyotoU.
“We also successfully measured the rate at which the galaxy distribution gradually becomes denser due to gravity, which is consistent with the general theory of relativity,” said Teppei Okumura of the Academia Sinica Institute of Astronomy and Astrophysics.
“Our research has proven general relativity in the distant universe, but the nature of dark energy or the origin of cosmic acceleration remains unresolved,” Okumura added.
The archived data — obtained from the Sloan Digital Sky Survey and the Baryon Oscillation Spectroscopic Survey — consists of three samples of galaxies selected for their brightness and distance. In addition, 3D positions and shape information for each galaxy helped to measure the magnitude of the alignment relative to distant galaxies.
The results of the team’s model were confirmed by theoretical calculations and gave Taruya and Okumura strong evidence that the orientations of these galaxies are related to each other, presenting a stronger case for in general relativity on a cosmological scale.
“Current efforts, such as the Subaru Telescope project, will provide extremely high-quality, high-precision observational data. These will lead to cutting-edge research in cosmology using intrinsic alignments to shed light on the nature of characteristic of dark energy,” Taruya said.
Reference: “First Growth Rate Constraints from Redshift-space Ellipticity Correlations of SDSS Galaxies at 0.16 < z < 0.70" by Teppei Okumura and Atsushi Taruya, 13 March 2023, The[{” attribute=””>Astrophysical Journal Letters.
DOI: 10.3847/2041-8213/acbf48
