The first deep-field image of the cosmos taken by the James Webb Space Telescope (JWST) has allowed scientists to study the faint, almost ghostly light of orphan stars that exist between the galaxies of galactic clusters.
Gravitationally unbound to galaxies, these stars are pulled from their homes and drift through intergalactic space by the massive tidal forces generated between cluster galaxies. The light emitted by these stellar orphans is called intracluster light, and it is so faint that it has only one percent of the brightness of the darkest sky that can be seen on Earth.
Not only could studying this ghostly light from orphan stars reveal how galactic clusters form, it could give scientists clues to the properties of dark matter, the mysterious substance that makes up about 85% of the mass of the universe.
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Dark matter does not interact with light, which means scientists know it is not the same as ordinary matter made up of protons and neutrons. Its presence can currently only be inferred by its gravitational interactions which literally prevent the stars and planets of galaxies from separating.
The JWST views the universe in infrared light, frequencies of electromagnetic radiation that allow astronomers to see galactic clusters differently from the picture painted in visible light.
The sharpness of the JWST infrared images allowed Instituto de Astrofísica de Canarias (IAC) researchers Mireia Montes and Ignacio Trujillo to study intracluster light from the galactic cluster SMACS-J0723.3–7327 in unprecedented detail.
This sharpness comes from the fact that JWST images of SMACS-J0723.3–7327, which is located about 4 billion light-years from Earth in the constellation Volans, are twice as deep as observations of the same cluster. previously taken by the Hubble Space Telescope.
“In this study, we show the great potential of JWST to observe such a faint object,” said the research’s first author, Montes, in a statement. statement (opens in a new tab). “This will allow us to study galaxy clusters much further away and in much greater detail.”
However, studying this low intracluster light required more than just the observational power of the JWST, which meant the team also had to develop new image analysis techniques. “In this work, we needed to perform additional processing on the JWST images to be able to study the intracluster light, since it is a weak and extensive structure,” Montes explained in the release. “It was essential to avoid bias in our measurements.”
The data obtained by the scientists is a striking demonstration of the potential of intracluster light to reveal the processes behind structure formation in galactic clusters.
“Analyzing this diffuse light, we find that the inner parts of the cluster are formed by a merger of massive galaxies, while the outer parts are due to the accretion of galaxies similar to our Milky Way,” Montes said.
Moreover, since intracluster stars follow the gravitational influence of the cluster as a whole rather than that of individual galaxies, the light from these stellar orphans presents an excellent means of studying the distribution of dark matter in these clusters.
“The JWST will allow us to characterize the distribution of dark matter in these huge structures with unprecedented precision and shed light on its fundamental nature,” added the study’s second author, Trujillo.
The duo’s research was published Dec. 1 in Astrophysical Journal Letters. (opens in a new tab).
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