Hubble throws light on missing dark matter SCIENCE DAILY

In 2018, an international team of researchers using the NASA and European Space Agency’s Hubble space telescope and several other observatories uncovered, for the first time, a galaxy that is missing most of its dark matter.

The discovery of galaxy NGC 1052-DF2 was a surprise to astronomers, as it was understood that dark matter is a key constituent in current models of galaxy formation and evolution.

Without the presence of dark matter, the primordial gas would lack enough gravitational pull to start collapsing and forming new galaxies, scientists say.

But a year later, another galaxy that misses dark matter was discovered, NGC

1052- DF4, which further triggered intense debates among astronomers about the

By studying the galaxy’s light, the astronomers also found evidence of tidal tails, which are formed of the material moving away from NGC 1052-DF4.

Now, new Hubble data have been used to explain the reason behind the missing dark matter in NGC 1052-DF4, which resides 45 million light-years away. Mireia Montes of the University of New South Wales in Australia led an international team of astronomers to study the galaxy using deep optical imaging.

They discovered that the missing dark matter can be explained by the effects of tidal disruption. The gravity forces of the neighboring massive galaxy NGC 1035 are tearing NGC 1052-DF4 apart.

During this process, the dark matter is removed, while the stars feel the effects of the interaction with another galaxy at a later stage.

Until now, the removal of dark matter in this way has remained hidden from astronomers as it can only be observed using extremely deep images that can reveal extremely faint features.

“We used Hubble in two ways to discover that NGC 1052-DF4 is experiencing an interaction,” explained Montes. “This includes studying the galaxy’s light and the galaxy’s distribution of globular clusters.”

Thanks to Hubble’s high-resolution images, the astronomers could identify the galaxy’s globular cluster population. The 10.4- meter Gran Telescopio Canarias (GTC) telescope and the IAC80 telescope in the Canary Islands of Spain were also used to complement Hubble’s observations by further studying the data.

“It is not enough just to spend a lot of time observing the object, but a careful treatment of the data is vital,” explained team member Raúl Infante-Sainz of the

Instituto de Astrofísica de Canarias in Spain.

By studying the galaxy’s light, the astronomers also found evidence of tidal tails, which are formed of the material moving away from NGC 1052- DF4.

This further supports the conclusion that this is a disruption event. Additional analysis concluded that the central parts of the galaxy remain untouched and only about seven percent of the stellar mass of the galaxy is hosted 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 starting to be stripped as well.

PHOTOGRAPH COURTESY OF NASA/ESA HUBBLE as seen from space.

PHOTOGRAPH COURTESY OF NASA/ESA GALAXY NGC 2525 photographed by the Hubble space telescope.