Here is a bit more detail on their discovery:

It is located in the Ursa Major constellation and is so far away that its light took 9.8 billion years to reach us.

“We think the giant galaxy at the centre of SpARCS1049+56 is furiously making new stars after merging with a smaller galaxy,” said Dr Tracy Webb of McGill University, who is the lead author of a paper published in the Astrophysical Journal.

“It is very exciting to have discovered such an interesting object,” said co-author Prof Gillian Wilson of the University of California, Riverside.

Congratulations to the team and we are looking forward to more data and insight from their discovery.

And this is a general background on galaxy clusters from wikipedia:

A galaxy cluster or cluster of galaxies is a structure that consists of anywhere from hundreds to thousands of galaxies bound together by gravity.^[1] They are the largest known gravitationally bound structures in the universe and were the largest known structures in the universe until the 1980s when superclusters were discovered.^[2] One of the key features of clusters is the intracluster medium or ICM. The ICM consists of heated gas between the galaxies and has a temperature on the order of 7-9 keV. Galaxy clusters should not be confused with star clusters such as open clusters, which are structures of stars within galaxies, as well asglobular clusters, which typically orbit galaxies. Small aggregates of galaxies are referred to as groups of galaxies rather than clusters of galaxies.

thanks to sci-news.com for the great info

thanks to NASA for the pic