A little trick turned James Webb into a “hunter” dark matter🇧🇷 By detecting extragalactic light in galaxy clusters, an infrared telescope can reveal the distribution of this invisible matter and provide us with a new view of the universe.
Dark matter is one of the biggest challenges in physics, as it is the only way to interact with baryonic matter (“normal” matter, which includes everything we can observe in any way).
Scientists are confident that dark matter exists because it has mass and thus interacts gravitationally. In fact, observations of galaxies, gravitational lensing, and galaxy clusters can only be explained by the addition of dark matter to their surroundings.
Extragalactic light and dark matter
Today astronomers know that this invisible matter is behind the formation and evolution of galaxies. One clue (pictured below) is gravitational lensing – when a very distant galaxy gets magnified by the group of galaxies closest to us. But these lenses consist of more mass than one would expect if dark matter were excluded.
Astronomers are also detecting the presence of dark matter in X-ray (pink) and baryonic matter (blue) maps of different groups of colliding galaxies (image below). The map shows a clear separation between normal matter and gravitational effects, which is one of the strongest evidence for dark matter.
This does not mean that dark matter appears in the images. What’s going on is a little more complicated, but neat. X-rays reveal, in this case, where galaxy collisions create temperatures of hundreds of thousands of degrees, creating light coming from outside the galaxies but from within the cluster.
This light is called “intergalactic light,” because the source is stars and other phenomena — including the collision of matter at galaxy mergers — outside individual galaxies. But not all intergalactic light is caused by baryonic matter processes alone.
When galaxies within clusters interact, stars and tidal currents are removed from the galaxies to which they belong. Although we cannot distinguish these individual stars, they still shine brightly, emitting a faint intergalactic light.
As dark matter gravitationally attracts these stars, the light evolves as a tracker of dark matter, as in the case of the Tadpole Galaxy. Its massive tail is evidence of tidal interactions — when some gravitational force pulls and stretches galactic material, creating a filament that contracts under its own gravity to form stars.
In the case of the Tadpole galaxy, the tail is about 280,000 light-years across and detects stars by following the distribution of dark matter in that region, creating intergalactic light.
Although they can detect dark matter with these techniques, telescopes still can’t provide enough detailed data for deeper study. That may change with the James Webb Telescope.
James Webb discovers dark matter
In a new study published in Astrophysical Journal Letters By researchers Mireya Montes and Ignacio Trujillo, the James Webb telescope with intergalactic light observation technology was used to study dark matter.
The pair used the first deep field image from JWST and calibrated the data to extract more information about the intergalactic light. In the 3-frame animation below, we see the original deep field image, an inverted color version, and a contrast/brightness-enhanced version to improve intergalactic light.
They found light from mergers and luminous additions caused by external factors. There are many lights that come from outside the cluster of galaxies and get confused with the light inside the cluster, but the duo managed to separate them all and eliminate the luminosity of the outer objects.
The remaining light indicates that galaxy mergers within clusters are the main source of intergalactic light made up of stars. Because matter emitted by this luminosity responds to dark matter, the study authors show that the dark matter-tracking technique is excellent if James Webb data is used.
This technology already exists with other infrared telescopes, but James Webb is the most powerful of them all. This means: we may have a lot of news about dark matter in the universe in the near future.
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