Intracluster light refers to diffuse light from stars which are not gravitationally bound to any individual galaxies but the halo surrounding galaxy clusters. Astronomers discovered that intracluster light is a fraction of total galaxy cluster light. This was based on a study of 10 clusters measuring 10 billion light years away.
When a galaxy orbits the centre of a cluster, it can scatter stars outside their galactic birthplace.
Drag pushes dust and gas out of the galaxy. Based on Hubble’s new survey James Jee, Yonsei University Astronomer, and his collaborators rule this out as the main cause of the star formation.
This is because the intracluster fraction of light would rise over time to the current if stripping were the primary player.
However, this is not true in Hubble’s new data which shows a steady fraction across billions of years.
We don’t know exactly what caused them to become homeless. “Our results cannot be explained by current theories, but they are produced in large numbers in the early Universe,” Dr. Jee stated.
Galaxies may have had a small formative year, and could have bled stars easily due to a weaker gravitational grasp.
Hyungjin Joo, Yonsei University Astronomer, said, “If we find out the origins of intracluster star, it will allow us to understand the assembly history an entire galaxy cluster and can serve as visible tracers of dark matter surrounding the cluster.”
Dark matter, also known as the invisible scaffolding that holds the Universe together, is what holds galaxies and clusters of them together.
“If wandering stars had been produced by a pinball game between galaxies relatively recently, then they wouldn’t have enough time scatter across the whole gravitational field and would therefore not be able to trace the distributions of dark matter in the cluster.”
But if stars are born early in the cluster, then they will be fully distributed throughout the cluster.
This would enable us to map the distribution of dark matter across the cluster using the stars that are wayward.”
The technique, which measures how light is reflected from background objects by the cluster’s entire cluster due to gravitational lensing, is new and complements the conventional method of dark matter mapping.
These findings were published by the journal Nature.
H. Joo & M.J. Jee. 2023. At redshift beyond unity, there is abundant intracluster light. Nature 613, 37-41; doi: 10.1038/s41586-022-05396-4