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Astronomers using NASA / ESA’s Hubble Space Telescope have detected tidal tails in NGC 1052-DF4, a dark matter-free galaxy about 65 million light-years away in the constellation Cetus, caused by its interaction with the galaxy nearby NGC 1035. Researchers think a process called tidal disruption ripped dark matter from NGC 1052-DF4 and is now tearing apart the galaxy.
This Hubble image shows the ultra diffuse galaxy NGC 1052-DF4; the highlighted objects are globular clusters. Image credit: van Dokkum et al, doi: 10.3847 / 2041-8213 / ab0d92.
Dark matter is a key constituent in current patterns of galaxy formation and evolution.
Indeed, without the presence of dark matter, the primordial gas would not have sufficient gravity to start collapsing and forming new galaxies.
Since this dark matter is thought to interact primarily in a gravitational way, its presence can only be inferred from its effect on visible matter.
In 2018, astronomers discovered the first known galaxy without dark matter, NGC 1052-DF2.
A year later, another galaxy devoid of dark matter, NGC 1052-DF4, was identified, which further sparked intense debates among astronomers about the nature of these objects.
In the new study, astronomer Mireia Montes and colleagues from the University of New South Wales studied NGC 1052-DF4 using deep optical images.
They found that the missing dark matter can be explained by the effects of the disruption of the tides.
According to the team, gravity forces from the nearby massive galaxy NGC 1035 are tearing apart NGC 1052-DF4.
During this process, dark matter is removed, while the stars feel the effects of interacting with another galaxy at a later stage.
“We used Hubble in two ways to find that NGC 1052-DF4 is experiencing an interaction,” said Dr Montes.
“This includes studying the light of the galaxy and the distribution of globular clusters.”
This image presents the region around the galaxy NGC 1052-DF4, taken by the IAC80 telescope of the Teide Observatory in Tenerife. The image shows the major galaxies in the field of view, including NGC 1052-DF4 (center of image) and its huge neighbor NGC 1035 (center left). Image credit: Montes et al., doi: 10.3847 / 1538-4357 / abc340.
By studying the galaxy’s light, astronomers have found evidence of tidal tails, which are formed from material moving away from NGC 1052-DF4 – this further supports the conclusion that this is the tidal disruption process.
They also found that the central parts of the galaxy remain intact and only 7% of the galaxy’s stellar mass is housed in these tidal tails.
This means that dark matter, which is less concentrated than stars, was previously and preferentially stripped from the galaxy, and now the outer stellar component is also starting to be stripped.
“This result is a good indicator that while the galaxy’s dark matter has evaporated from the system, the stars are only now starting to undergo the breaking mechanism,” said Dr. Ignacio Trujillo, astronomer of the Instituto de Astrofísica. de Canarias.
“In time, NGC 1052-DF4 will be cannibalized by the great system around NGC 1035, with at least some of their stars floating free in deep space.”
The results are published in Astrophysical Journal.
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Mireia Montes et al. 2020. The “Missing Dark Matter” galaxy NGC 1052-DF4 is experiencing tidal interruptions. ApJ 904, 114; doi: 10.3847 / 1538-4357 / abc340
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