The invisible halo that surrounds and permeates a galaxy or galaxy cluster is called a dark matter halo
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A University of California, Riverside physicist explains.
In a research study co-led by physicists at the University of California, Riverside and the University of California, Irvine, it was found that the dark matter halos of ultra-diffuse galaxies are really odd, raising concerns about the present understanding of galaxy development and the universes structure.
The name “ultra-diffuse galaxies” refers to their extremely low luminosity. When compared to “normal” galaxies of comparable mass, the distribution of baryons– gas and stars– in ultra-diffuse galaxies is considerably more spread out.
In this sense, dark matter halos of the ultra-diffuse galaxies are “odd.”.
They found that ultra-diffuse galaxies rotate more gradually than typical galaxies with comparable masses. We analyzed information from simulations of cosmic structure formation and determined dark matter halos that have similar properties as those inferred from the ultra-diffuse galaxies.
Ultra-diffuse galaxies contain a lot of gas and we do not know how this gas is retained during galaxy formation. Further, our results indicate that these galaxies may be younger than regular galaxies.
Hai-Bo Yu is a theoretical physicist at UC Riverside. Credit: Samantha Tieu.
In the following Q&A, Hai-Bo Yu, an associate professor of physics and astronomy at UCR, discusses the findings he and UCIs Manoj Kaplinghat, a long-term colleague of Yus, released in The Astrophysical Journal regarding freshly discovered ultra-diffuse galaxies and their dark matter halos.
Demao Kong of Tufts University, along with Filippo Fraternali and Pavel E. Mancera Pia of the University of Groningen in the Netherlands, teamed up with Yu and Kaplinghat on the research study. Kong, the first author, will sign up with UCR this fall.
Q. What is a dark matter halo?
A dark matter halo is the halo of invisible matter that permeates and surrounds a galaxy or a cluster of galaxies. Dark matter has actually never ever been discovered in labs, physicists are confident dark matter, which makes up 85% of the universes matter, exists.
Q. Youve discovered dark matter halos of the ultra-diffuse galaxies are really odd. What is odd about them and what are you comparing them to?
The ultra-diffuse galaxies we studied are much less enormous compared to, say, the Milky Way. They include a lot of gas, nevertheless, and they have much greater gas mass than overall excellent mass, which is opposite to what we see in the Milky Way. The ultra-diffuse galaxies likewise have big sizes.
The distribution of dark matter in these galaxies can be inferred from the motion of gas particles. What really surprises us is that the presence of baryonic matter itself, primarily in the kind of gas, is almost adequate to discuss the measured velocity of gas particles and leaves little space for dark matter in the inner areas, where the majority of the stars and gas lie.
This is very surprising since, in the case of typical galaxies, whose masses are similar to those of ultra-diffuse galaxies, its the reverse: dark matter dominates over baryonic matter. To accommodate this result, we conclude that these dark matter halos need to have much lower “concentrations.” That is, they contain much less mass in their inner areas, compared to those of regular galaxies. In this sense, dark matter halos of the ultra-diffuse galaxies are “odd.”.
Initially glance, one would anticipate that such low-concentration halos are so uncommon that the ultra-diffuse galaxies would not even exist. After checking out the data from modern mathematical simulations of cosmic structure development, nevertheless, we discovered the population of low-concentration halos is higher than the expectation.
Q. What was associated with doing the study?
They discovered that ultra-diffuse galaxies turn more gradually than regular galaxies with comparable masses. We analyzed information from simulations of cosmic structure formation and recognized dark matter halos that have comparable homes as those inferred from the ultra-diffuse galaxies.
Q. Your findings raise questions about our understanding of galaxy formation/structure formation of the universe. How?
We have numerous questions relating to the development and evolution of these freshly discovered galaxies. For example, ultra-diffuse galaxies include a great deal of gas and we do not know how this gas is maintained throughout galaxy development. Even more, our results suggest that these galaxies may be younger than typical galaxies. The formation of the ultra-diffuse galaxies is not well understood, and more work is needed.
Q. What makes ultra-diffuse galaxies so interesting?
These are incredible things to study since of their surprising residential or commercial properties, as talked about in our work. The newly found ultra-diffuse galaxies supply a brand-new window for further testing our understanding of galaxy development, probably even the nature of dark matter.
Referral: “The Odd Dark Matter Halos of Isolated Gas-rich Ultradiffuse Galaxies” by Demao Kong, Manoj Kaplinghat, Hai-Bo Yu, Filippo Fraternali and Pavel E. Mancera Piña, 12 September 2022, The Astrophysical Journal.DOI: 10.3847/ 1538-4357/ ac8875.
The study was funded by the National Science Foundation, the United States Department of Energy, the John Templeton Foundation, and NASA.