NASA | GSFC | STScI | HubbleSite | 2023 Jan 04
In giant clusters of hundreds or thousands of galaxies, innumerable stars wander among the galaxies like lost souls, emitting a ghostly haze of light. These stars are not gravitationally tied to any one galaxy in a cluster.Science Credits: NASA, ESA, STScI, James Jee (Yonsei University);
Image Processing: Joseph DePasquale (STScI)
The nagging question for astronomers has been: how did the stars get so scattered throughout the cluster in the first place? Several competing theories include the possibility that the stars were stripped out of a cluster's galaxies, or they were tossed around after mergers of galaxies, or they were present early in a cluster's formative years many billions of years ago.
A recent infrared survey from NASA's Hubble Space Telescope, which looked for this so-called "intracluster light," sheds new light on the mystery. The new Hubble observations suggest that these stars have been wandering around for billions of years, and are not a product of more recent dynamical activity inside a galaxy cluster that would strip them out of normal galaxies.
The survey included 10 galaxy clusters as far away as nearly 10 billion light-years. These measurements must be made from space because the faint intracluster light is 10,000 times dimmer than the night sky as seen from the ground.
The survey reveals that the fraction of the intracluster light relative to the total light in the cluster remains constant, looking over billions of years back into time. ...
Ghost Light Among Galaxies Stretches Far Back In Time
ESA Hubble | 2023 Jan 04
Intracluster light is already abundant at redshift beyond unity ~ Hyungjin Joo & M. James Jee
- Nature 613(7942):37 (05 Jan 2023) DOI: 10.1038/s41586-022-05396-4 (pdf)