NASA’s James Webb House Telescope (JWST) has produced a brand new picture of the Bullet Cluster, which is a titanic collision between two particular person galaxy clusters.
The picture, produced at the side of NASA’s Chandra X-ray Observatory, reveals not solely the placement and mass of dark matter current, but additionally factors the way in which towards in the future determining what darkish matter is definitely manufactured from.
Within the new picture, we see the new fuel throughout the Bullet Cluster in false-color pink, detected by Chandra. The inferred location of darkish matter is represented in blue (additionally false shade), as measured by the JWST. Word that the blue and the pink are separate — what has induced the darkish matter and the fuel to separate, and the way have been astronomers capable of produce this map of the fabric throughout the Bullet Cluster?
Positioned 3.9 billion light-years away, the Bullet Cluster has been an sometimes controversial poster little one for dark-matter research. Again in 2006, the Hubble Space Telescope and the Chandra X-ray Observatory labored collectively to picture the Bullet, exhibiting the presence of its darkish matter based mostly on how mild from extra distant galaxies was being gravitationally lensed by the darkish matter’s mass.
Collisions between galaxy clusters are the right laboratories for testing our concepts about darkish matter, as a result of they’re nature’s approach of throwing collectively large quantities of the stuff. This provides us an opportunity to check how darkish matter particles work together with one another, if in any respect, and the diploma of any interplay could be an enormous clue as to the properties of the mysterious darkish matter particle.
But regardless of the dramatic Hubble and Chandra photos, the Bullet Cluster — and, certainly, different galaxy cluster collisions — have not all the time performed ball. For example, the velocities at which the sub-clusters are colliding appear too excessive for the usual mannequin of cosmology to clarify.
Now the JWST has entered into the fray. A workforce led by Ph.D. pupil Sangjun Cha of Yonsei College in Seoul, South Korea, and professor of astronomy James Jee at each Yonsei and the College of California, Davis, have used essentially the most highly effective house telescope ever constructed to get a best-ever have a look at the Bullet Cluster.
Hubble and Chandra had beforehand proven that, as the 2 particular person galaxy clusters within the Bullet Cluster collided, the galaxies and their surrounding darkish matter haloes had handed proper by way of one another. This is sensible for the galaxies — the distances between them are so nice that the prospect of a head-on collision between any two is slim. It additionally means that the diploma with which darkish matter particles work together with one another — what we check with as their collisional cross part — is small; in any other case, the interplay would have slowed the clouds of darkish matter down, and we’d detect it nearer to the place Chandra sees the new, X-ray emitting intracluster fuel. In distinction to the darkish matter, these large fuel clouds cannot get out of one another’s approach, in order that they slam into one another and do not progress any additional.
The top result’s that the new fuel is discovered caught in the midst of the collision, and the galaxies and darkish matter belonging to every sub-cluster are discovered on reverse sides, having glided proper by way of each other.
“Our JWST measurements help this,” Jee informed House.com. “The galaxy distribution carefully traces the darkish matter.”
JWST was capable of produce a greater map of the distribution of matter, each strange and darkish, within the Bullet Cluster by detecting, for the primary time, the mixed glow from billions of stars which were thrown out of their galaxies and are actually free-floating within the house between the galaxies in every sub-cluster. Cha and Jee’s workforce have been then ready to make use of the sunshine from these “intracluster stars” to hint the presence of darkish matter and acquire a extra correct map of its distribution within the Bullet Cluster.
Nevertheless, this has simply raised extra mysteries. The extra refined map of the darkish matter reveals that, within the bigger sub-cluster, on the left, the darkish matter is organized in an elongated, “hammerhead” form that, in keeping with Jee, “can’t be simply defined by a single head-on collision.”
This elongated mass of darkish matter is resolved into smaller clumps centered on what we name the brightest cluster galaxies — big elliptical galaxies which might be the brightest galaxies within the sub-cluster positioned at its gravitational core. In distinction, the darkish matter halo across the sub-cluster on the alternative aspect is smaller and extra compact.
Cha and Jee’s workforce suspect that the elongated, clumpy mass of darkish matter may solely have fashioned when that exact sub-cluster, which was a galaxy cluster in its personal proper earlier than the Bullet collision, underwent an analogous collision and merger with one other galaxy cluster billions of years earlier than the formation of the Bullet.
“Such an occasion would have stretched and distorted the dark-matter halo over time, ensuing within the elongated morphology that we observe,” stated Jee.
Regardless of the brand new discoveries akin to this from JWST’s extra refined observations of the Bullet cluster, it’s nonetheless not sufficient to resolve the difficulty of the collision velocities of the 2 sub-clusters.
“Even with these updates, the required collision velocity stays excessive relative to expectations from cosmological simulations,” stated Jee. “The strain persists and stays an energetic space of analysis.”
Darkish matter makes up over 1 / 4 of all of the mass and power within the universe, and roughly 85% of all matter, so determining its secrets and techniques, particularly its collisional cross-section and the reason for these excessive velocities, goes to be important if we wish to higher perceive this universe wherein we stay.
Alas, the JWST observations of the Bullet Cluster alone will not be sufficient to substantiate what the collisional cross-section of darkish matter should be. Nevertheless, they do tighten the estimate of the higher restrict for the worth of the cross-section, constraining the record of potentialities.
Astronomers are already within the means of rigorously measuring as many galaxy cluster collisions as potential, seen from all angles and distances, to attempt to constrain this worth additional. Step by step, we’ll have the ability to rule out completely different fashions for what darkish matter could possibly be, till we’re left with only a few. Coupled with experimental information from direct darkish matter searches from detectors deep underground, such because the LUX-ZEPLIN experiment on the Sanford Underground Analysis Facility in South Dakota, we may quickly be on the cusp of answering certainly one of science’s best mysteries: what’s darkish matter?
The JWST observations have been reported on June 30 in The Astrophysical Journal Letters.