Distant galaxies line up in support of Einstein’s general relativity

Scientists have confirmed that the intrinsic alignment of galaxies can probe dark matter and dark energy on a cosmic scale, supporting general relativity on vast spatial scales. However, the nature of dark energy and cosmic acceleration remains unresolved.

Einstein would nod in agreement. General relativity can be applied to even the most remote regions of the universe.

Now, scientists from international research institutions, including Kyoto University, have confirmed that the intrinsic alignments of galaxies have properties that allow them to be a powerful probe of dark matter and dark energy on a cosmic scale.

By gathering evidence that the distribution of galaxies more than tens of millions of light-years away is subject to the gravitational effects of dark matter, the team succeeded in testing the general theory of gravity on vast spatial scales. The international team analyzed the positions and orientations of galaxies, obtained from archived data of 1.2 million galactic observations. With the help of the available 3D positional information for each galaxy, the resulting statistical analysis quantitatively characterized to what extent the orientation of the more distant galaxies is aligned.

“This alignment, which mainly results from interactions with nearby objects, was considered as systematic noise in measuring the weak lensing effect,” says lead author Atsushi Taruya of the Yukawa Institute for Theoretical Physics in Kyoto.

“We also succeeded in measuring the rate at which the galaxy distribution becomes progressively denser due to gravity, which is consistent with the general theory of relativity,” says Teppei Okumura of the Academia Sinica Institute for 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 adds.

The archived data — obtained from the Sloan Digital Sky Survey and the Baryon Oscillation Spectroscopic Survey — consists of three sample galaxies selected for their brightness and distance. In addition, the 3D locations and shape information for each galaxy helped measure the magnitude of the alignment relative to distant galaxies.

The team’s model results were supported by theoretical calculations and gave Taruya and Okumura strong evidence that the orientations of these galaxies are related, demonstrating a stronger case for general relativity on a cosmological scale.

Current endeavors, such as the Subaru Telescope project, will provide high-quality, high-resolution observational data. This will lead innovative cosmological research using intrinsic alignment to shed light on the nature of dark energy,” notes Taruya.

Reference: “First constraints on the growth rate from elliptic correlations of the space redshift of SDSS galaxies at 0.16 the Astrophysical Journal Letters.
DOI: 10.3847/2041-8213/acbf48