A little trick turned James Webb into a “hunter” for 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 perspective on the universe.
Dark matter is one of the biggest problems in physics because it is the only way to interact with baryonic matter (“normal” matter, which includes everything we can observe in any way).
Scientists are confident in the existence of dark matter because it has mass and therefore interacts gravitationally. In fact, observations of galaxies, gravitational lensing, and clusters of galaxies can only be explained by adding dark matter to their surroundings.
Extragalactic light and dark matter
Astronomers today know that this invisible matter is behind the formation and evolution of galaxies. One piece of evidence (pictured below) is gravitational lensing—when a very distant galaxy is enlarged by a cluster of galaxies closest to us. But these lenses are made up of more mass than would be expected if we ruled out dark matter.
Astronomers are also detecting the presence of dark matter in X-ray (pink) and baryonic (blue) maps of various clusters of colliding galaxies (image below). The map shows a clear separation between ordinary matter and gravitational effects, which is one of the strongest evidence for the existence of dark matter.
This does not mean that dark matter appears in the images; what happens is a little more complicated, but elegant. The X-rays in this case show where galaxy collisions create temperatures in excess of a few hundred thousand degrees, creating light that comes from outside the galaxies but inside the cluster.
This light is called “intergalactic light” because it comes from stars and other phenomena, including matter colliding in galaxy mergers, outside of individual galaxies. But not all intergalactic light is the result of only these processes with baryonic matter.
When galaxies interact within clusters, stars and tidal currents are removed and sent away from the galaxies they belong to. Although we cannot distinguish these individual stars, they still glow, emitting a faint intergalactic light.
As dark matter gravitationally pulls on these stars, light evolves as a dark matter trailblazer, as is the case with the Tadpole galaxy. Its massive tail is evidence of tidal interactions – when some kind of gravitational force pulls and stretches galactic matter, forming a filament that contracts under its own gravity, forming stars.
In the case of the Tadpole galaxy, the tail is roughly 280,000 light-years long, and it shows the stars, following the distribution of dark matter in that region, creating intergalactic light.
Despite the possibility of detecting dark matter with these methods, telescopes have so far not been able to provide enough detailed data for an even deeper study. This may change with the James Webb telescope.
James Webb discovered dark matter
In a new study published in Letters from an astrophysical journal researchers Mireya Montes and Ignacio Trujillo used the James Webb telescope with the method of observing intergalactic light to study dark matter.
The pair used the first deep field image from JWST and calibrated the data to extract more information about intergalactic light. In the three-frame animation below, we see the original deep field image, a color inverted version, and a version with enhanced contrast/brightness to enhance intergalactic light.
They found light created by light fusions and additions caused by external factors. There are many lights coming from outside the cluster of galaxies and entangled with the light within the cluster, but the duo managed to separate them all and eliminate the luminosity of the outer objects.
The remaining light suggests that galactic mergers within clusters are the primary source of star-forming intergalactic light. Because the matter that emits this luminosity responds to dark matter, the authors of the study showed that the dark matter tracking method is superior if James Webb’s data is used.
This technique has already existed with other infrared telescopes, but James Webb is the most powerful of them all. That is: we may have a lot of news about the dark matter of the universe in the near future.
Source: POPPY, Starts with a bang