Tuesday , August 16 2022

NASA’s Galaxy Hubots Dots Removed From Dark Matter


Dark matter theory has long been a sacrosanct in mainstream astronomical circles. Astronomers rarely contradict the principle that about 85 percent of all matter in the cosmos is dominated by an unseen matter that only interacts weakly with gravity.

It was, therefore, surprising that its existence was cast into doubt by recent Hubble Space Telescope observations of two massive galaxies that seemed completely devoid of this exotic matter.

But in a paper presented to The Astrophysical Journal, an international team of scientists details observations of NGC 1052-DF4, the second galaxy allegedly harboring little or no such dark matter. They argue that NGC 1052-DF4, a massive galaxy some 45 million light years away in the southern constellation of Cetus, is almost completely removed from this strange matter by gravitational interaction with its neighboring galactic neighbor, NGC 1035.

In fact, NASA claims that the forces driving NGC 1035 to interfere with NGC 1052-DF4 tear the latter apart.

Deep optical imaging of NGC 1052-DF4 has revealed that tidal disturbances occur in this galaxy, write the authors, caused by its interaction with its neighbor, NGC 1035. Dark matter is less concentrated than stars, and therefore during interactions it is better extracted from the satellites of galaxies, they report.

How does such stripping really work?

Like chalkboard friction on a blackboard, said Mireia Montes, a postdoctoral fellow at the University of New South Wales in Australia and lead author of the paper. As you write with the chalk, the chalk particles are deposited in the direction of your script, he said.

By rote, as the galaxy continues to interact with its massive galactic neighbor, the stripped chalk particles would be deposited in the direction of the galaxy’s orbit, Montes said. In this case, what we can see is that NGC 1052-DF4 stars are actually starting to be removed from their host galaxy, he said.

Such research provides case studies of how and why large galaxies actually form. Dark matter helps to form galaxies because it provides a type of the gravity well where ordinary matter can sit and cool and form stars, Montes said.

It also acts as a protective shield. Without this dark matter shield, Montes says, the galaxy would be very unstable and prone to gravitational influence from outside forces. So, he says, such galaxies would not survive in an environment where more massive galaxies swallow these dark galaxies that have matter stripes.

We also know from simulations that the dark matter content must decrease by about 90 percent for the interaction to start affecting the stars, he said.

These more accurate observations also provided new distance measurements to the galaxy, NGC 1052-DF2. In 2018, a team of Yale University astronomers noted that NGC 1052-DF2 is also devoid of dark matter. But these new observations unravel that mystery.

We argue instead that a closer distance to the galaxy than the one measured in 2018 solves the peculiarities of the dark matter of the NGC 1052-DF2 galaxy, Montes said. But closer distance does not help in the case of NGC 1052-DF4; it is still missing dark matter, he said.

And for physics as we know it to work, theorists still need a dark issue.

Without the presence of dark matter, there would be insufficient gravitational pull to primordial gas to start collapsing and forming new galaxies, Montes said. And once a galaxy is removed from its dark matter, Montes says this exotic matter becomes part of a galaxy responsible for the stripping. In this case, that would be the spiral galaxy similar to a NGC 1035 cigar.

“In time, NGC 1052-DF4 will be cannibalized by the large system around NGC 1035, with at least some of their stars floating free in deep space,” said team member Ignacio Trujillo Instituto de Astrof√≠sica de Canarias in Spain, in a statement.

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