A tiny, mysterious galaxy 44 million light-years away is finally producing its secrets. Last year turned out to be a shockingly low amount of dark matter, which posed a significant challenge to our models of the Galaxy NGC 1052-DF4A Galaxy formation.
Those models still live another day. According to new research, NGC 1052-DF4 lacks really dark matter – but only because another nearby galaxy has blossomed.
“The dark matter is not there because it is already gone,” said Mirea Montes, ast astrophysicist at the University of New South Wales and the Space Telescope Science Institute in Australia.
“We have found that its stars and dark matter are removed by pulling gravity from the nearby giant galaxy NGC1035.”
(Montes et al., APJ, 2020)
The discovery of the NGC 1052-DF4 (or DF4 for short) was announced last year, and it was immediately followed by a flurry of astronomical pickles. It was the second galaxy of its kind – an obscure, ultra-diffuse galaxy or UDF – found in severely dark-matter decay. The first was NGC 1052-DF2, and DF4 confirmed that galaxies with insufficient dark matter existed.
The problem was that, according to our current data, dark matter is needed to make galaxies in the first place.
We don’t know what a dark object is, and we can’t find it directly, but we do know that most galaxies have more gravity than their normal, detectable objects. There are some hidden masses in the universe that make it an extra gravitational pull, and without it, according to our understanding of galaxy formation, the child would not have enough gravity to break up objects to form galaxies.
The matter seemed closer to a resolution when the team of astrophysicists saw that DF2 was actually closer to us than previously thought. This means that it has a much smaller mass than the initial calculations suggested, and the proportion of normal matter was much lower. Once the calculations based on the corrected distance were completed, DF2 had a fairly normal amount of dark matter.
They then turned their attention to DF4. That, too, seemed very close… but something was still not quite right. The velocity of the clusters of stars inside the galaxy still indicates that there was much less dark matter than there should have been.
Stupid galaxies are very hard to see, so Montes and his colleagues booked time on some of the most powerful telescopes in the world to find out.
Using the IAC 80 telescope, the Gran Telescopio Canaria, and the Hubble Space Telescope, they detected and detected stars by pulling them out of DF4, consistent with interactions with many large spiral galaxies NGC 1035. This process, in which the large body “disrupts” gravity, is known as a small, tidal disruption.
“Preliminary papers showed that the galaxy has a very ‘relaxed’ symmetrical shape, indicating that no outside forces are disturbing it.”
“But our deep ND images show that this galaxy is in fact being influenced by its neighboring galaxy – it caught on at the very beginning of the interaction. The interior of the galaxy has its own shape, but the outer, obscure parts where you see these ‘tidal tails’: Which are already separated from the galaxy. “
Tidal tails got streaming from DF4. (Montes et al., APJ, 2020)
Montez noted that as dark matter surrounds galaxies in a vast halo, these tidal bars will remove the dark matter of small galaxies before affecting the stars. Stars begin to strip only when the black matter content falls below 10 to 15 percent of the total mass of the galaxy.
It is consistent with the team’s observations. UDF contains more dark matter – about 99 percent of the galaxy’s mass. In the case of DF4, the team estimates that dark matter makes up only one percent of the total mass.
Because the dark matter is basically a gravitational glue that holds the galaxy together, this also means that the time of DF4 in this universe is limited.
“Over time, NGC 1052-DF4 will be extruded by the vast system surrounding NGC 1035, with at least some of its stars floating in deep space,” said Ignacio Trujillo, an astrophysicist at the Instituto de str Stroffísica de Caneria.
But at least we don’t have to go back to the drawing board on the Galaxy formation.
Research has been published in Astrophysical Journal.
.
