Why are the dark matter halos of super-diffuse galaxies so strange?

لماذا هالات المادة المظلمة للمجرات فائقة الانتشار غريبة جدًا؟

Left: Rthe above-Fifththe above Distributions inferred from the readout scales (coloured), along with those from the TNG50-1-Dark simulation (grey circles). Solid black lines show the median relationship (Diemer & Joyce 2019), as well as 0.3 and 0.6 dex greater Rthe above (“lower concentration”) compared to the average. The black dashed lines indicate the record of aura blocks10(M200/ M0 = 10, 10.5 and 11. IllustrisTNG halos are selected within the red box for further study in the right panel. Right: halo circular velocity at 8 kpi (upper panel) and 2 kpi (lower panel) radius vs. maximum circular velocity of observed UDGs (color symbols according to the graphic key in the left panel), compared to the selected TNG50 -1- Dark halos (gray halos). attributed to him: Astrophysical Journal (2022). DOI: 10.3847 / 1538-4357 / ac8875

A study co-led by physicists at UC Riverside and UC Irvine has found dark matter halos in ultra-diffuse galaxies to be very strange, raising questions about physicists’ understanding of the formation of galaxies and the structure of the universe.

Galaxies are called highly diffuse because of their extremely low luminosity. The distribution of baryons—gas and stars—is more common in ultra-diffuse galaxies than in “normal” galaxies of similar mass.

In the following Q&A, Hai-Bo Yu, associate professor of physics and astronomy at UCR, shares his thoughts on the findings that he and Manoj Kaplingat of the UCI, and his long-term collaborator, have published in Astrophysical Journal About newly discovered super-diffuse galaxies and their galaxies dark matter auras;

Yu and Kaplingat joined in the research Dimao Kong of Tufts University, and Filippo Fraternali and Pavel e Mancera Peña of the University of Groningen in the Netherlands. First author Kong will join UCLA this fall.

Q: What is a dark matter aura?

a dark matter aura A halo of invisible matter that permeates and surrounds a galaxy or group of galaxies. Although dark matter has never been detected in laboratories, physicists are confident that dark matter, which makes up 85% of the matter of the universe, is present.

Q: I have found the dark matter halos of ultra-diffuse galaxies to be very strange. What is strange about them and what do you compare them to?

The ultra-diffuse galaxies we studied are much less massive than, say, the Milky Way. However, it does contain a lot of gas, and it has a gas mass much higher than the total stellar mass, which is the opposite of what we see in the Milky Way. Ultra-diffuse galaxies are also large in size.

The distribution of dark matter in these galaxies can be inferred from the motion of gas molecules. What really surprises us is that the presence of baryonic matter itself, mostly in gas form, is almost sufficient to explain the measured velocity of gas particles and leaves little room for dark matter in the interior, where most of the stars and gas are.

This is surprising because in the case of ordinary galaxies, whose masses are similar to that of ultra-diffuse galaxies, the opposite is true: dark matter predominates over baryonic matter. To accommodate this result, we conclude that these dark matter halos must have much lower ‘concentrations’. That is, they have much less mass in their inner regions, compared to that of ordinary galaxies. In this sense, the dark matter halos of super-diffuse galaxies are “alien”.

At first glance, one might expect that such low-focus halos are so rare that even super-diffuse galaxies do not exist. After looking at data from the latest numerical simulations of cosmic structure formation, we found that the numbers of low-focus halos are higher than expected.

Q: What was included in the study procedure?

This is a collaborative work. Filippo Fraternali and his student Pavel y Mancera Peña are experts in gas dynamics in galaxies. They discovered that ultra-diffuse galaxies rotate more slowly than normal galaxies of similar masses. We worked together to interpret the measurement data for the gas motion of these galaxies and to infer the distribution of dark matter. Furthermore, we analyzed data from simulations of cosmic structure formation and determination Dark matter halos which have properties similar to those inferred from ultra-diffuse galaxies.

Q: Your findings raise questions about our understanding of the formation of galaxies/the formation of the structure of the universe. How?

We have many questions regarding the formation and evolution of these newly discovered galaxies. For example, super-diffuse galaxies contain a lot of gas and we don’t know how this gas is kept during galaxy formation. Moreover, our results suggest that these galaxies may be smaller than normal galaxies. The composition of super-diffuse galaxies is poorly understood, and more work is needed.

Q: What makes super-diffuse galaxies so interesting?

These are great things to study because of their amazing properties, as discussed in our work. Newly discovered ultra-diffuse galaxies provide a new window for further tests of our understanding of galaxy formation, and perhaps even the nature of dark matter.

Hubble sees a stranger in the galaxy

more information:
Demao Kong et al, Strange dark matter halos from isolated gas-rich, massive galaxies, Astrophysical Journal (2022). DOI: 10.3847 / 1538-4357 / ac8875

the quoteWhy are the dark matter halos of super-diffuse galaxies so strange? (2022, September 12) Retrieved September 12, 2022 from https://phys.org/news/2022-09-dark-halos-ultra-diffuse-galaxies-odd.html

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