14 March 2017 10:04

Astronomers have sampled 40,000 distant galaxies to better understand how galaxies like our own Milky Way have formed and evolved across cosmic time.

Dr David Sobral from Lancaster University is a member of an international team led by a joint collaboration between the California Institute of Technology (Caltech) and the University of California, Riverside.

The team looked at the COSMOS field (where CR7 was also discovered), a large patch of sky with deep enough data to look at galaxies very far away, and with accurate distance measurements to individual galaxies.

Dr Sobral said: "We have studied over 40 thousand galaxies and catalogued the cosmic web in large scales into its main components within the COSMOS field: clusters, filaments, and sparse regions devoid of any object. It’s remarkable how state-of-the-art data and methods now allow us to extend our analysis into a much younger universe, and probe such structures up to 8 billion years back in time.”

The galaxies were then divided into those that are central to their local environment (the centre of gravity) and those that roam around in their host environments (satellites).

The scaffolding that holds the large-scale structure of the universe constitutes galaxies, dark matter and gas (from which stars are forming), organized in complex networks known as the cosmic web.

This network comprises dense regions known as galaxy clusters and groups that are woven together through thread-like structures known as filaments. These filaments form the backbone of the cosmic web and host a large fraction of the mass in the universe, as well as sites of star formation activity.

While there is ample evidence that environments shape and direct the evolution of galaxies, it is not clear how galaxies behave in the larger, global cosmic web and in particular in the more extended environment of filaments.

Behnam Darvish a postdoctoral scholar at Caltech who is the lead author on the paper, said: “What makes this study unique is the observation of thousands of galaxies in different filaments spanning a significant fraction of the age of the Universe”.

Other authors include Nick Scoville and Shoubaneh Hemmati of Caltech, Andra Stroe of the European Southern Observatory, and Jeyhan Kartaltepe of the Rochester Institute of Technology.

The research in the Astrophysical Journal was funded by NASA.