To the Heart of 3C 273

International Team Observes Innermost Structure of a Quasar Jet

November 22, 2022

At the heart of nearly every galaxy lurks a supermassive black hole. But not all supermassive black holes are alike: there are many types. Quasars (or quasi-stellar objects) are one of the brightest and most active types of galaxies that host supermassive black holes.

An international group of scientists including astronomers at the Max Planck Institute for Radio Astronomy presents new observations of the first quasar ever identified. Its name is 3C273 and it is located at a distance of approx. 1.9 Billion light years in the Virgo constellation. The new high-resolution radio images trace the jet down to the jet formation region and show how the width of the jet varies with distance from the central black hole.

The results are published in the current issue of the “Astrophysical Journal”.

Fig. 1: The views of the 3C 273 jet from the deepest to farthest ends. The left image shows the deepest look yet into the plasma jet of the quasar 3C 273, which will allow scientists to further study how quasar jets are collimated, or narrowed. The powerful, collimated jet extends for hundreds of thousands of light-years beyond the host galaxy, as seen in the right panel optical image taken by the Hubble Space Telescope. Scientists use radio images at different scales to measure the shape of the entire jet. The radio interferometer arrays used are the Global Millimeter VLBI Array (GMVA) joined by the Atacama Large Millimeter/submillimeter Array (ALMA) and the High Sensitivity Array (HSA). — **Fig. 1:** The views of the 3C 273 jet from the deepest to farthest ends. The left image shows the deepest look yet into the plasma jet of the quasar 3C 273, which will allow scientists to further study how quasar jets are collimated, or narrowed. The powerful, collimated jet extends for hundreds of thousands of light-years beyond the host galaxy, as seen in the right panel optical image taken by the Hubble Space Telescope. Scientists use radio images at different scales to measure the shape of the entire jet. The radio interferometer arrays used are the Global Millimeter VLBI Array (GMVA) joined by the Atacama Large Millimeter/submillimeter Array (ALMA) and the High Sensitivity Array (HSA).

© Hiroki Okino and Kazunori Akiyama; GMVA+ALMA and HSA images: Okino et al.; HST Image: ESA/Hubble & NASA.

**Fig. 1:** The views of the 3C 273 jet from the deepest to farthest ends. The left image shows the deepest look yet into the plasma jet of the quasar 3C 273, which will allow scientists to further study how quasar jets are collimated, or narrowed. The powerful, collimated jet extends for hundreds of thousands of light-years beyond the host galaxy, as seen in the right panel optical image taken by the Hubble Space Telescope. Scientists use radio images at different scales to measure the shape of the entire jet. The radio interferometer arrays used are the Global Millimeter VLBI Array (GMVA) joined by the Atacama Large Millimeter/submillimeter Array (ALMA) and the High Sensitivity Array (HSA).

© Hiroki Okino and Kazunori Akiyama; GMVA+ALMA and HSA images: Okino et al.; HST Image: ESA/Hubble & NASA.

Active supermassive black holes emit narrow, incredibly powerful jets of plasma that escape at nearly the speed of light. Thomas Krichbaum, astronomer at the Max Planck Institute for Radio Astronomy (MPIfR) in Bonn, Germany, one of the leading authors of the work, says: “These jets have been studied over many decades, yet the details of jet formation are not well understood and a topic of ongoing research. An unresolved issue has been how and where the jets are collimated into a narrow beam, which allows them to propagate to extreme distances beyond their host galaxy. Astronomers now realize that these far outreaching jets may even affect galactic evolution. These new radio observations are probing as deep as 0.5 light years into the heart of the black hole in 3C273 into the region, where the jet plasma flow is collimated into a narrow beam.”

This new study, published today in The Astrophysical Journal, includes observations of the 3C 273 jet at the highest angular resolution to date. The ground-breaking work was made possible by using a closely coordinated set of radio antennas around the globe, a combination of the Global Millimeter VLBI Array (GMVA) and the Atacama Large Millimeter/submillimeter Array (ALMA) in Chile. In addition, coordinated observations were also made with the High Sensitivity Array (HSA) to extend the study of 3C 273 to larger scales, in order to also measure the global shape of the jet. The data in this research were collected in 2017, around the same time that the Event Horizon Telescope (EHT) observations revealed the first images of a black hole in M87, which is a radio galaxy about 20 times closer than 3C273.

The MPIfR is the leading institution of the GMVA. Data are processed at the correlator center in the institute, and the observations are coordinated from the institute.

“3C 273 has been studied for decades as the ideal closest laboratory for quasar jets,” says Hiroki Okino, lead author of this paper and a PhD student at the University of Tokyo and National Astronomical Observatory of Japan. “However, even though the quasar is a close neighbor, until recently, we didn’t have an eye sharp enough to see where this narrow powerful flow of plasma is shaped.”

The image of the 3C 273 jet gives scientists the very first view of the innermost part of the jet in a quasar, where the collimation or narrowing of the beam occurs. The team further found that the angle of the plasma stream flowing away from the black hole is tightened up over a very long distance. This narrowing part of the jet continues incredibly far, well beyond the area where the black hole’s gravity rules.

“It is striking to see that the shape of the powerful stream is slowly formed over a long distance in an extremely active quasar. This has also been discovered nearby in much fainter and less active supermassive black holes,” says Kazunori Akiyama, research scientist at MIT Haystack Observatory and project lead. “The results pose a new question: how does the jet collimation happen so consistently across such varied black hole systems?”

The new, extremely sharp images of the 3C 273 jet were made possible by the inclusion of the ALMA interferometer, which was phased-up to act as a single big radio-telescope. The GMVA and ALMA were connected across continents using a technique called very long baseline interferometry (VLBI) to obtain highly detailed information about distant astronomical sources. The remarkable VLBI capability of ALMA was enabled by the ALMA Phasing Project (APP) team. The international APP team, led by MIT Haystack Observatory and the MPIfR, developed the hardware and software to turn ALMA, an array of sixty-six telescopes, into the world’s most sensitive astronomical interferometry station. Collecting data at these wavelengths greatly increases the resolution and sensitivity of the VLBI array. This capability was fundamental not only to the GMVA but also to the EHT’s black hole imaging work.

Anton Zensus, director at the MPIfR and coauthor of the present work, concludes: “ALMA joining the global VLBI networks is a complete game-changer for black hole science. With this breakthrough, we obtained the first-ever images of supermassive black holes, and now in cases like 3C 273 it is helping us to see for the first time incredible new details about how black holes power their jets also in such more distant objects.”

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Additional Information:

GMVA: The Global Millimeter-VLBI Array (GMVA) observes at 3 mm wavelength, using the following stations for this research in April 2017: eight antennas of Very Long Baseline Array (VLBA), the Effelsberg 100-m Radio Telescope of the Max Planck Institute for Radio Astronomy (MPIfR), the IRAM 30-m Telescope, the 20-m telescope of the Onsala Space Observatory, and the 40-m Radio Telescope of Yebes Observatory. The data were correlated at the DiFX VLBI correlator at the MPIfR in Bonn, Germany.

ALMA: The Atacama Large Millimeter/submillimeter Array (ALMA) is a partnership of European Southern Observatory (ESO, representing its member states), NSF (USA), and NINS (Japan), together with NRC (Canada), MOST and ASIAA (Taiwan), and KASI (Republic of Korea), in cooperation with the Republic of Chile. The Joint ALMA Observatory is operated by ESO, AUI/NRAO, and NAOJ. This work makes use of the following ALMA data: ADS/JAO.ALMA2016.1.01216.V.

APP: Partner organizations of the ALMA Phasing Project (APP) include: MIT Haystack Observatory, USA; Max-Planck-Institut für Radioastronomie (MPIfR), Germany; University of Concepción, Chile; National Astronomical Observatory of Japan (NAOJ), Japan; National Radio Astronomy Observatory (NRAO), USA; Institute of Astronomy & Astrophysics, Academia Sinica (ASIAA), Taiwan; Onsala Space Observatory, Sweden; Harvard-Smithsonian Center for Astrophysics (CfA), USA; University of Valencia, Spain. Funding for the APP was provided by the National Science Foundation Major Research Instrumentation Program, the ALMA North America Development Program, and international cost-sharing partners.

VLBA: The Very Long Baseline Array (VLBA) is an instrument of the National Radio Astronomy Observatory.

NRAO: The National Radio Astronomy Observatory (NRAO) is a facility of the National Science Foundation operated under cooperative agreement by Associated Universities, Inc.

The research team comprises Hiroki Okino, Kazunori Akiyama, Keiichi Asada, José L. Gómez , Kazuhiro Hada, Mareki Honma , Thomas P. Krichbaum, Motoki Kino, Hiroshi Nagai, Uwe Bach, Lindy Blackburn, Katherine L. Bouman, Andrew Chael, Geoffrey B. Crew, Sheperd S. Doeleman, Vincent L. Fish, Ciriaco Goddi, Sara Issaoun, Michael D. Johnson, Svetlana Jorstad, Shoko Koyama, Colin J. Lonsdale, Ru-Sen Lu, Ivan Martí-Vidal, Lynn D. Matthews, Yosuke Mizuno, Kotaro Moriyama, Masanori Nakamura, Hung-Yi Pu, Eduardo Ros, Tuomas Savolainen, Fumie Tazaki, Jan Wagner, Maciek Wielgus,ó and Anton Zensus. Thomas P. Krichbaum, Uwe Bach, Ru-Sen Lu, Eduardo Ros, Tuomas Savolainen, Jan Wagner, Maciek Wielgus, and J. Anton Zensus are affiliated to the MPIfR.