BUFFALO charge to the first galaxies

The NASA / ESA Hubble Space Telescope has launched a new mission to shed light on the evolution of the first galaxies in the Universe. The BUFFALO survey will observe six clusters of massive galaxies and their environment. The first observations show the Abell 370 galaxy group and a host of gravitational lens magnified galaxies all around.

The cluster of Abell 370 galaxies was the first target of the BUFFALO survey, which aims to search some of the first galaxies in the universe. Credit: NASA, ESA, A. Koekemoer, M. Jauzac, C. Steinhardt and the BUFFALO Team

Getting to know the formation and evolution of the very first galaxies of the Universe is crucial for our understanding of the cosmos. While the Hubble Space Telescope NASA / ESA has already detected some of the most distant galaxies known, their number is small, making it difficult for astronomers to determine whether they represent the universe as a whole.

Clusters of massive galaxies like Abell 370, visible in this new image, can help astronomers find more of these distant objects. Huge clusters of galaxies make them cosmic loupes. The mass of a cluster bends and magnifies the light from more distant objects behind it, uncovering objects too faint, even for Hubble's sensitive vision. Using this cosmological trick – called a strong gravitational lens – Hubble is able to explore some of the oldest and furthest galaxies in the Universe.

The mass of Abell 370 allows to focus many galaxies. The most amazing demonstration of the gravitational lens is just below the center of the cluster. Nicknamed "the dragon", this extended feature consists of a multitude of duplicate images of a spiral galaxy beyond the cluster.

This image of Abell 370 and its surroundings was carried out as part of the new survey "Beyond Ultra-Deep Border Fields and Heritage Observations" (BUFFALO). The project, led by European astronomers from the Niels Bohr Institute (Denmark) and the University of Durham (UK), was designed to succeed the successful Frontier Fields project. [1]. 101 Hubble orbits – corresponding to 160 hours of valuable observation time – were spent exploring the six galaxy clusters of Frontier Field. These additional observations focus on the regions surrounding clusters of galaxies, allowing for a larger field of view.

The main mission of BUFFALO however is to study how and when the most massive and luminous galaxies of the Universe were formed and how the formation of ancient galaxies is related to the assembly of dark matter. This will allow astronomers to determine how quickly galaxies have formed in the 800 million years since the Big Bang – opening the way for observations with the upcoming NASA / ESA / CSA James Webb Space Telescope .

Guided by Frontier Fields observations, BUFFALO will be able to detect the most distant galaxies about ten times more efficiently than its ancestor. The BUFFALO survey will also take advantage of other space telescopes that have already observed areas around clusters. These datasets will be included in the search for the first galaxies.

Extended fields of view will also enable better three-dimensional mapping of mass distribution – both ordinary matter and dark matter – in each cluster of galaxies. These maps help astronomers to learn about the evolution of galaxy clusters and the nature of dark matter.