The first deep-field image of the cosmos captured by the James Webb Space Telescope (JWST) has given scientists the opportunity to study the faint almost-light from orphan stars that exist between galaxies in galactic clusters.
Unbound by the galaxies’ gravity, these stars break free from their homes and are propelled into intergalactic space by the great tidal forces generated between the galaxies in the clusters. The light emitted by these orphan stars is called intracluster light and is so dim that it possesses only one percent of the brightness of the darkest sky visible to Earth.
Not only could the study of this faint light from orphan stars reveal how galactic clusters form, but also reveal to scientists the properties of dark matter, the mysterious substance that accounts for about 85% of the total mass.
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Dark matter does not correspond to light in the sense that scientists know it is not the same as everyday matter composed of protons and neutrons. Its presence can only be inferred by the gravitational interactions that literally prevent the stars and planets of the galaxy from flying apart.
JWST sees the universe in infrared light, a frequency of electromagnetic radiation that allows astronomers to see galaxy clusters differently from the picture depicted in visible light.
The power of JWST’s infrared images has allowed Instituto de Astrofísica de Canarias (IAC) researchers Mireia Montes and Ignacio Trujillo to study the intracluster light from the galaxy cluster SMACS-J0723.3-7327 at a unique level.
This insight 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 high as observations of the same cluster previously taken by Hubble. Space Telescope.
“In this study we have shown the great potential of JWST to observe such a faint object,” researches first author Montes, in n. it is said (Opens in a new tab). “Here we study galaxy clusters that are much more distant and much more abundant.”
Studying this faint intracluster light required more than the sheer power of JWST to maintain it, however, meaning the team also developed new image analysis techniques. “In this work, we need to do some processing on the JWST images to be able to study the intracluster light as a thin and extended structure,” Montes explained in a statement. “This was key to avoid bias in the measurements.”
The data obtained by the scientists is an excellent demonstration of the power of intracluster light to reveal the process behind the formation of structure in galaxy clusters.
“By shedding this diffuse light, we found that the interior of the cluster was formed by the merger of massive galaxies, while the outer parts were formed due to the accretion of galaxies similar to our own Milky Way,” Montes said.
In addition, because the intracluster stars follow the gravity of the cluster as a whole rather than the individual galaxies, the light from these orphan stars is excellent for probing the distribution of dark matter in these clusters.
“The JWST will distinguish the dark matter in these enormous structures with extraordinary precision, and shed light on their fundamental nature,” attributed the study’s second author, Trujillo.
The duo’s research was published in Astrophysical Journal Letters on Dec. 1 (Opens in a new tab).
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