Heidelberg University Astronomers Study Early Space With Images From James Webb Space Telescope

Using the observations of a distant, very luminous galaxy, an international research team has discovered a cluster of galaxies with the aid of the James Webb Space Telescope (JWST) and, at the same time, one of the densest known areas of galaxy formation in the early Universe. The observations from the new space telescope revealed a galaxy protocluster forming in the region around a quasar. This emerging galaxy cluster could give information about how galaxies in the early Universe evolved into the cosmic network visible today. Dr Dominika Wylezalek, a scientist at the Centre for Astronomy of Heidelberg University (ZAH), was in charge of the research work.

The focus of the investigations was a galaxy with a very active, luminous core, which is fed by a supermassive black hole at the heart of the galaxy. It is assumed that such a core, known as a quasar, can launch a “galactic wind” that pushes the gas out of the host galaxy. These outflows of matter could thereby influence the formation of other stars and galaxies. The international research team led by Dr Wylezalek observed the quasar SDSS J165202.64+172852.3 – J1652 for short – with the James Webb Space Telescope. The quasar existed back in the very early Universe, that is, about 11.5 billion years ago. Its striking red light was shifted into the infra-red due to its large distance and the expansion of the Universe. Hence quasar J1652 is particularly suited to observations with the James Webb telescope, which was designed especially for observations in this spectral range.

Previous investigations showed that fast gas outflows are driven by the quasar and found evidence for the merging of the quasar with a neighbouring galaxy. Surprisingly, the observations with the JWST confirm that not only one galaxy but at least three more are swirling around at high speed and are tightly packed. Scientists also call such a system a galaxy protocluster – a cluster of galaxies in formation. The objects in the direct environment of the quasar were analysed with infrared spectroscopy. According to Dr Wylezalek, they indicate that J1652 is part of a dense knot of galaxy formation. This conclusion is only possible due to the outstanding imaging and spectroscopic capabilities of the James Webb Space Telescope. “There are few galaxy protoclusters known at this early time. They are hard to find and very few have had time to form since the Big Bang. Our discovery may help us understand how galaxies in dense environments evolve,” says the astrophysicist. “We are looking into the earliest phases of the evolution of these galaxies.”

The international researcher team suggests that they have discovered one of the densest known areas of galaxy formation in the early Universe – taking account of the speed at which the three confirmed galaxies are orbiting each other and how closely they are packed into the region around the quasar. “Even a dense knot of dark matter is not sufficient to explain the properties we have observed. We think we could be seeing a region in which two knots of dark matter are merging together,” says the scientist, who heads an Emmy Noether junior research group at Heidelberg University’s Institute for Astronomical Computing, which belongs to the ZAH. From follow-up observations she hopes to understand how dense, chaotic galaxy clusters like this one form and how they evolved to become the cosmic network visible today. With her team, to which postdoctoral researcher Dr Caroline Bertemes also belongs, Dr Wylezalek first wants to discover how the protocluster is affected by galactic winds and quasar feedback generated by the active, supermassive black hole at its heart.

Besides the Heidelberg team, other scientists from Germany, France, the UK, Mexico and the United States were involved in the research. The observations with the James Webb Space Telescope took place as part of the Early Release Science Programme within the first five months after the start of JWST scientific operations. The German Research Foundation, the Daimler and Benz Foundation and the German Aerospace Center supported the research carried out at Heidelberg University. The results were published in “The Astrophysical Journal Letters”.