The unusual structure of the Spiderweb Galaxy

Galaxy formation and evolution is a fascinating topic. Astronomers don’t know exactly how galaxies form. Large galaxies are often home to hundreds of billions of stars, but when a mega galaxy is observed at a fraction of the age of the universe, astronomers still wonder how it is possible that such mega structures form in such a short amount of cosmic time.

The spiderweb galaxy is such a structure. We observe the Spiderweb galaxy as it was just shy of 4 billion years after the big bang. In cosmic terms, that’s early, given that the universe is now almost 14 billion years old. There is a very massive galaxy at the centre of the Spiderweb, which harbours a supermassive black hole at the centre, visible to us as an active galactic nucleus (AGN). This large galaxy is surrounded by an immense cloud of cold gas, where ltst of smaller galaxies are being attracted by the central one, forming a huge structure called a proto-cluster. What is unusual about it, is that the formation of new stars is happening in the cloud of gas around the galaxy, like flies in a spider’s web, hence the name.

New observations made from the Atacama Pathfinder EXperiment telescope reveal more interesting views of the Spirderweb galaxy. ( The APEX telescope operates between infrared light and radio waves. This allows the telescope to study cold, dusty gas in the distant universe. Because such light is absorbed by the Earth’s atmosphere, the telescope is built at high altitude in the Atacama desert in the Andean mountains in Chile. The higher the altitude, the thinner the layer of atmosphere the light needs to travel through before hitting the telescope.

A team of astronomers, including Sthabile Kolwa, a previous postdoctoral researcher at IDIA made those observations, by pushing the envelope of what the telescope is capable of. When analysing the observations, the team of co-authors looked at what the element of Carbon is doing in the galaxy. They looked at carbon atoms that are stripped of one electron, which called CII. Their main finding is that this type of carbon is found both in the AGN, and in the cloud of gas surrounding the central galaxy, and the ionised carbon shines brighter around the galaxy than at its centre.

This observation is one of few that shows both a galactic centre component and a component in the cloud of gas surrounding the AGN in a galaxy this far away. Now, very distant galaxies from the early universe can be better compared and studied and maybe we’ll figure out how these early universe gargantuan galaxies form?

Feeding the spider with carbon — [CII] emission from the circum galactic medium and active galactic nucleus, Carlos De Breuck (ESO), Andreas Lundgren (ESO), Bjorn Emonts (NRAO), Sthabile Kolwa (University of Johannesburg), Helmut Dannerbauer (IAC), Matthew Lehnert(University de Lyon), accepted by Astronomy & Astrophysics Letters, arXiv:2201.05064

Cover photo: Source. This image shows the full ACS overview of the region around the Spiderweb Galaxy (just to the right of the center). The galaxy is sitting at the centre of an emergent galaxy cluster, surrounded by hundreds of other galaxies from the cluster.
Image credit: NASA, ESA, G. Miley and R. Overzier (Leiden Observatory), and the ACS Science Team
Acknowledgement: Davide De Martin (ESA/Hubble).