Press release
March 29, 2023
Astronomers using the Atacama Large Millimeter/submillimeter Array (ALMA), in which ESO is involved, have discovered a large reservoir of hot gas in the still-forming galaxy cluster around the Spiderweb galaxy. This is the most distant detection of such hot gas to date. Galaxy clusters are among the largest known objects in the universe. The result, published today in Nature, shows how these structures form.
As their name suggests, galaxy clusters are home to a large number of galaxies, sometimes even thousands. In addition, they contain a huge “Intracluster environment(ICM) consisting of gas that permeates the space between the galaxies in the cluster. In fact, this gas weighs much more than the galaxies themselves. Much of the physics of galaxy clusters is well understood, but there are few observations of the early stages of ICM formation.
Until now, the ICM has only been studied in nearby, fully developed galaxy clusters. The discovery of the ICM in distant protoclusters, i.e. galaxy clusters that are still forming, would allow astronomers to study these clusters in the early stages of their formation. A team led by Luca Di Mascolo, lead author of the study and a researcher at the University of Trieste, Italy, wanted to detect the ICM in a protocluster from the earliest phase of the universe.
Galaxy clusters are so massive that they can accumulate gas, which heats up as it falls toward the cluster. “Cosmological simulations have predicted the presence of hot gas in protoclusters for more than a decade, but lack observational confirmation,” says Elena Rasia, a researcher at the Italian National Institute of Astrophysics (INAF) in Trieste, Italy, and co-author of the study.The search for such important experimental confirmation led us to carefully select one of the most promising protocol candidates.“This is the Spiderweb Protocluster, which was created at a time when the universe was only 3 billion years old. Although it is the most studied protocluster, the existence of the ICM is difficult to prove. The discovery of a large reservoir of hot gas in the Spiderweb protocluster suggests that the system is on track to become a true long-lived galaxy cluster rather than disintegrating.
Di Mascolo’s team discovered the Spiderweb protocol’s ICM through the so-called thermal Sunyaev-Zeldovich (SZ) effect. This effect occurs when light from the cosmic microwave background, the relic radiation from the Big Bang, passes through the ICM. When this light reacts with fast electrons in the hot gas, it gains a little energy and its color, or wavelength, changes slightly.At the right wavelengths, the SZ effect therefore appears as a shadow effect of a galaxy cluster on the cosmic microwave background.” explains Di Mascolo.
So by measuring these shadows against the cosmic microwave background, astronomers can locate the hot gas, estimate its mass, and map its shape.Thanks to its unparalleled resolution and sensitivity, ALMA is the only facility currently capable of performing such a measurement for the distant progenitors of massive star clusters.said Di Mascolo.
They found that the Spiderweb protocol contains a huge reservoir of hot gas with a temperature of several tens of millions of degrees Celsius. Cold gas had already been discovered in this protocol, but the mass of hot gas found in this new study exceeds it by a thousand times. This discovery shows that the Spiderweb protocol will evolve into a massive galaxy cluster in about 10 billion years, increasing its mass by at least ten times.
Tony Mroczkowski, co-author of the study and researcher at ESO, explains: “This system has huge contrasts. The warm thermal component will destroy much of the cold component as the system evolves and we are seeing a critical transition.He concludes that “The observations confirm long-standing theoretical predictions about how the largest gravitationally bound objects in the universe form.“
These results help lay the foundations for synergies between ALMA and the upcoming Extremely Large Telescope (ELT) of ESO, the “will revolutionize the study of structures such as the spider websays Mario Nonino, co-author of the study and researcher at the Astronomical Observatory of Trieste. The ELT and its cutting-edge instruments such as HARMONY And MICADO will be able to peer inside the protocols and tell us in great detail about the galaxies they contain. Combined with ALMA’s ability to capture the forming ICM, this will provide crucial information about the composition of some of the largest structures in the early Universe.
Further information
This research was presented in the paper “Intracluster gas formation in a protocluster of galaxies at redshift 2.16,” published in Nature (doi: 10.1038/s41586-023-05761-x).
The team is composed of Luca Di Mascolo (Department of Astronomy, University of Trieste, Italy (UT); INAF – Astrophysical Observatory of Trieste, Italy (INAF Trieste); IFPU – Institute for Fundamental Physics of the Universe, Italy ( IFPU)), Alexandro Saro (UT; INAF Trieste; FIPU; INFN – Trieste Section, Italy (INFN)), Tony Mroczkowski (European Southern Observatory, Germany (ESO)), Stefano Borgani (UT; INAF Trieste; FIPU; INFN) , Eugene Churazov (Max Planck of Astrophysics, Germany; Space Research Institute, Russia), Elena Rasia (INAF Trieste; FIPU), Paolo Tozzi (INAF – Osservatorio Astrofisico di Arcetri, Italy), Helmut Dannerbauer (Instituto de Astrofísica de Canarias , Spain; Universidad de La Laguna, Spain), Kaustuv Basu (Argelander Institute for Astronomy, University of Bonn, Germany), Christopher L. Carilli (National Radio Astronomy Observatory, USA), Michele Ginolfi (ESO; Department of Physics and Astronomy, University of Florence, Italy) , George Miley (Leiden Observatory, Leiden University, Netherlands), Mario Nonino (UT), Maurilio Pannella (UT; INAF Trieste; FIUP), Laura Pentericci (INAF – Astronomical Observatory of Rome, Italy), Francesca Rizzo ( Cosmic Dawn Center, Denmark; Niels Bohr Institute, Denmark).
The Atacama Large Millimeter/submillimeter Array (ALMA) is an international astronomical facility jointly managed by ESO, the National Science Foundation (NSF) of the United States and the National Institutes of Natural Sciences of Japan (NINS), in cooperation with the Republic of Chile. ALMA is supported by ESO on behalf of its Member Countries, by NSF in cooperation with the National Research Council of Canada (NRC), the National Science and Technology Council (NSTC) and NINS in cooperation with the Academia Sinica (AS) in Taiwan and the Korea Institute of Astronomy and Space Science (KASI). In terms of development, construction and operation, ESO leads the European contribution, the National Radio Astronomy Observatory (NRAO), which is in turn operated by Associated Universities, Inc. (AUI), the North American contribution, and the National Astronomical Observatory of Japan (NAOJ) for the East Asian contribution. The Joint ALMA Observatory (JAO) is responsible for the overall project management for ALMA construction, commissioning and observation operations.
The translations of ESO press releases into English are a service of the ESO Science Outreach Network (ESON), an international astronomy outreach network in which scientists and science communicators from all ESO Member Countries (and some other countries) are represented. It is the German node of the network. House of Astronomy in Heidelberg.
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Contact details
Luca Di Mascolo
University of Trieste
Trieste, Italy
E-mail: luca.dimascolo@units.it
Tony Mroczkowski
European Southern Observatory
Garching near Munich, Germany
Tel: +49 89 3200 6174
E-mail: tony.mroczkowski@eso.org
Alexander Saro
University of Trieste
Trieste, Italy
E-mail: asaro@units.it
Juan Carlos Muñoz Mateos
ESO Media Manager
Garching near Munich, Germany
Tel: +49 89 3200 6176
E-mail: press@eso.org
Markus Nielbock (press contact Germany)
ESO Science Outreach Network and House of Astronomy
Heidelberg, Germany
Tel: +49 6221 528-134
E-mail: eson-germany@eso.org
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This is a translation of ESO press release eso2304.