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How do supermassive black holes launch galaxy-size streams of high-energy particles – known as jets – into space at almost light-speed? Scientists have now taken an important step towards being able to answer this question, with intricate measurements of the centre of the galaxy NGC 1052, at a distance of 60 million light years from Earth in the direction of the constellation Cetus (the whale).

The research team made coordinated measurements using several radio telescopes, providing new insights into the workings of a galaxy and its supermassive black hole in the centre. Included are arrays of radio telescopes defining the Event Horizon Telescope (EHT) at 1.3 mm wavelength and the Global mm-VLBI Array (GMVA) at 3.5 mm. The technique which connects these telescopes is called very-long-baseline interferometry (VLBI).

“The centre of this galaxy, NGC 1052, is a promising target for imaging with the Event Horizon Telescope, but it’s faint, complex and more challenging than all other sources we’ve attempted so far”, says Anne-Kathrin Baczko, the main author of the publication. She is an astronomer at Onsala Space Observatory, Chalmers, and also affiliated to the Max-Planck-Institut für Radioastronomie (MPIfR).

The publication is the preliminary culmination of more than eight years of work, originally conceived at Julius-Maximilians-Universität Würzburg (JMU) by Matthias Kadler in collaboration with Eduardo Ros at MPIfR and then continued during the PhD thesis of Anne-Kathrin Baczko in Bonn under their joint supervision.

Two Jets Stretch Thousands of Light Years Through Space

The galaxy NGC 1052 hosts a supermassive black hole of about 150 million solar masses that is the source of two powerful jets which stretch thousands of light years outwards through space.

“We want to study not only the black hole itself and its extreme environment, but also the origin of the twin jets emanating from it. We have used the opportunity provided by GMVA and EHT to target a particularly important and key object, in the crossroads of different types of active galaxy,” says Eduardo Ros from MPIfR, a member of the research team.

Data From a Faint and Unknown Target

The team made measurements using just five of the telescopes in the EHT’s global network – including ALMA (the Atacama Large Millimeter/submillimeter Array) in Chile, in a configuration that would allow the best possible estimate of its potential for future observations and supplemented with measurements from other telescopes including the GMVA.

“For such a faint and unknown target, we were not sure if we would get any data at all. But the strategy worked, thanks in particular to the sensitivity of ALMA and complementary data from many other telescopes”, says Anne-Kathrin Baczko.

The scientists are now certain that successful imaging will be possible in the future, thanks to two new key findings. “Our results show that the region around the black hole where the twin jets form is large enough to be imaged with mm-VLBI observations. And it emits at exactly the right frequency of radio waves to take advantage of the strengths of the next generation of VLBI networks,” says Matthias Kadler from the JMU Würzburg.

Magnetic Field at the Black Hole is 400 Times Stronger than the Earth’s Magnetic Field

From their measurements, the scientists have also estimated the strength of the magnetic field close to the black hole’s event horizon. The field strength, 2.6 tesla, is about 400 times stronger than the Earth’s magnetic field. That’s consistent with previous estimates for this galaxy.

“This is such a powerful magnetic field that we think it can probably stop matter from falling into the black hole. That in turn can help to launch the galaxy’s two jets”, says Christian Fromm, also from JMU Würzburg and affiliated to the MPIfR.

Even though the source is as challenging as this, the future looks bright as radio astronomers prepare for much enhanced telescope networks such as the forthcoming NRAO’s new-generation Very Large Array (ngVLA) and future 1.3 mm arrays, with new antennas and improved equipment.

First-class Target for the Next Generation of Radio Telescopes

The new measurements give a clearer idea of how the innermost centre of the galaxy shines at different wavelengths. Its spectrum is bright enough at millimetre wavelengths yielding the very sharpest images and is even brighter around wavelength 2.3 mm, which makes it a prime target for the next generation of radio telescopes.

“With the Wetterstein Millimeter Telescope, we are aiming to build such a new radio telescope at the Zugspitze in Germany. This new telescope will improve the performance of upcoming international telescope networks enabling even more detailed information of how supermassive black holes launch relativistic jets”, states Matthias Kadler.

“Thanks to instruments like the EHT and the GMVA, we are now making remarkable observations that show the great progress in radio astronomy through technological innovation and international collaboration. Measurements at NGC1052, ranging from magnetic field strength to black hole environments, are providing valuable insights into the processes of jet formation and accretion,” says Anton Zensus, founding board chair of the EHT collaboration and director at the MPIfR. “With new telescopes and the next generation of networks, we will further deepen our understanding of these fascinating cosmic phenomena.”

“With the construction of the Wetterstein millimetre telescope, we want to build a new type of radio telescope on the Zugspitze in Germany that will improve the performance of future international telescope networks and thus provide even more detailed information on how supermassive black holes emit relativistic jets,” says Matthias Kadler.

Publication

The putative center in NGC 1052. Anne-Kathrin Baczko and 286 co-authors, Astronomy & Astrophysics, December 17, 2024, DOI: 10.1051/0004-6361/202450898, Open Access, https://www.aanda.org/10.1051/0004-6361/202450898

Additional Information

The EHT collaboration involves more than 400 researchers from Africa, Asia, Europe, North and South America, with around 270 participating in this paper. The international collaboration aims to capture the most detailed images of black holes using a virtual Earth-sized telescope. Supported by considerable international efforts, the EHT links existing telescopes using novel techniques to create a fundamentally new instrument with the highest angular resolving power that has yet been achieved.

The EHT consortium consists of 13 stakeholder institutes: the Academia Sinica Institute of Astronomy and Astrophysics, the University of Arizona, the Center for Astrophysics | Harvard & Smithsonian, the University of Chicago, the East Asian Observatory, the Goethe University Frankfurt, the Institut de Radioastronomie Millimétrique, the Large Millimeter Telescope, the Max Planck Institute for Radio Astronomy, the MIT Haystack Observatory, the ³Ô¹ÏÍøÕ¾ Astronomical Observatory of Japan, the Perimeter Institute for Theoretical Physics, and the Radboud University.

The measurements of NGC 1052 were made by five telescopes in the EHT network: ALMA (the Atacama Large Millimeter/submillimeter Array) in Chile, the IRAM 30-metre telescope in Spain; the James Clerk Maxwell Telescope (JCMT) and the Submillimeter Array (SMA) in Hawaii; and the South Pole Telescope (SPT) in Antarctica. These were supplemented with measurements from 14 other radio telescopes in the GMVA network (Global Millimetre VLBI Array), in Spain, Finland and Germany, including the 100-metre Effelsberg radio telescope, the 20-metre telescope at Onsala Space Observatory, Sweden, and the telescopes of the VLBA (Very Long Baseline Array) in the US.

Researchers affiliated with the Max Planck Institut für Radioastronomie, include Anne-Kathrin Baczko, the first author (main affiliation: Onsala Space Observatory, Chalmers University of Technology), and also Eduardo Ros, Christian M. Fromm, Maciek Wielgus, Thomas P. Krichbaum, Michael Janssen,Walter Alef, Rebecca Azulay, Uwe Bach, Silke Britzen, Gregory Desvignes, Sergio A. Dzib, Ralph Eatough, Ramesh Karuppusamy, Dong-Jin Kim, Joana A. Kramer, Michael Kramer, Jun Liu, Kuo Liu, Andrei P. Lobanov, Ru-sen Lu, Nicholas R. MacDonald, Nicola Marchili, Karl M. Menten, Cornelia Müller, Hendrik Müller, Aristeidis Noutsos, Gisela Ortiz-Leon, Georgios Filippos Paraschos, Felix Poetzl, Helge Rottmann, Alan L. Roy, Tuomas Savolainen, Lijing Shao, Pablo Torne, Efthalia Traianou, Jan Wagner, Robert Wharton, Gunther Witzel, J. Anton Zensus, and Guang-Yao Zhao.