Tuesday, June 13, 2017

Galaxy Alignments Traced Back Ten Billion Years

MACS J0416.1-240 is a cluster of galaxies located four billion light years away. A new study based on observations with the Hubble Space Telescope has shown that the most massive galaxies in the universe, which are found in clusters like this, have been aligned with the distribution of neighboring galaxies for at least ten billion years.

A new study led by Michael West of Lowell Observatory and Roberto De Propris of the University of Turku reveals that the most massive galaxies in the universe have been aligned with their surroundings for at least ten billion years. This discovery shows that galaxies, like people, are influenced by their environment from a young age.

Astronomers have long known that galaxies cluster together into enormous systems – the urban centers of the cosmos – and that the largest galaxies tend to ‘point’ towards their neighbors. But how and when these alignments occur remains a mystery.

Using the Hubble Space Telescope, the international team of collaborators peered across cosmic time to observe 65 distant galaxy clusters whose light has taken billions of years to reach Earth. They showed for the first time that the largest galaxies in these systems were already aligned with their surroundings when the universe was only 1/3 of its current age.

"Our results show that galaxy alignments were established very early in the universe’s history. It’s an important new piece to the puzzle because it says that whatever caused the alignments, it acted quickly," says De Propris.

Although clusters have hundreds or thousands of member galaxies, most are randomly oriented in space. Only the biggest galaxies are aligned with their surroundings, which suggests that they are especially sensitive to their environment.

The team is eager to look further back in time by observing more remote clusters. But studying galaxies at the dawn of the time is not easy, even with Hubble.

"We’re trying to measure the shapes and orientations of galaxies that appear very faint and very small because of their great distances, which is challenging," notes De Propris.

In addition to West and De Propris, the team includes Malcolm Bremer and Steven Phillipps, both at the University of Bristol.

Results of the study were published on June 12, 2017 via Advance Online Publication on Nature Astronomy’s website at http://dx.doi.org/10.1038/S41550-017-0157.

Credit: utu.fi

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