International team observes innermost structure of quasar jet | MIT News

At the heart of almost every galaxy lurks a supermassive black hole. But not all supermassive black holes are created equal: there are many types. Quasars, or quasi-stellar objects, are one of the brightest and most active types of supermassive black holes.

An international group of scientists has released new observations of the first-ever identified quasar, known as 3C 273, located in the constellation Virgo, showing the innermost, deepest parts of the quasar’s prominent plasma jet.

Active supermassive black holes emit narrow, incredibly powerful jets of plasma that escape at nearly the speed of light. These jets have been studied for many decades, but how they form remains a mystery to astronomers and astrophysicists. An unsolved problem has been how and where the jets will be collimated, or concentrated into a narrow beam, allowing them to extend to extreme distances beyond their host galaxy and even affect galactic evolution. These new observations are the deepest yet at the heart of a black hole, where the flow of plasma is collimated into a narrow beam.

This new study, published today in The Astrophysical Journal, includes observations of jet 3C 273 with the highest angular resolution yet, acquiring data for the innermost part of the jet near the central black hole. The groundbreaking work was made possible by deploying a tightly coordinated set of radio antennas around the world, a combination of the Global Millimeter VLBI Array (GMVA) and the Atacama Large Millimeter/submillimeter Array (ALMA) in Chile. Coordinated observations were also made using the High Sensitivity Array to study 3C 273 at different scales to also measure the global shape of the beam. The data in this study was collected in 2017, around the same time that observations from the Event Horizon Telescope (EHT) revealed the first images of a black hole.

The image of the 3C 273 jet gives scientists the first-ever look at the innermost part of the jet in a quasar, where collimation takes place. The team also found that the angle of the plasma stream flowing out of the black hole is narrowed over a very long distance. This narrowing part of the jet continues incredibly far, well beyond the region where the black hole’s gravity prevails.

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

“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 the National Astronomical Observatory of Japan. “Even though the quasar is a close neighbor, until recently we didn’t have an eye sharp enough to see where this narrow, powerful stream of plasma is being formed.”

The new, incredibly sharp images of the 3C 273 jet were made possible by the inclusion of the ALMA array. GMVA and ALMA were linked across continents using a technique called Very Long Baseline Interferometry (VLBI) to obtain highly detailed information about distant astronomical sources. ALMA’s remarkable VLBI capability was made possible by the ALMA Phasing Project (APP) team. The international APP team, led by MIT’s Haystack Observatory, developed the hardware and software to transform ALMA, an array of 66 telescopes, into the world’s most sensitive astronomical interferometry station. Collecting data at these wavelengths greatly increases the resolution and sensitivity of the array. This ability was also fundamental to the EHT’s black hole imaging work.

“The ability to use ALMA as part of global VLBI networks was a complete game changer for black hole science,” says Lynn Matthews, Principal Research Scientist at MIT’s Haystack Observatory and Contract Scientist for the APP. “It allowed us to get the first-ever images of supermassive black holes, and now it’s helping us see incredible new details about how black holes power their jets for the first time.”

This study opens the door for further exploration of ray collimation processes in other types of black holes. Data obtained with the EHT at higher frequencies, such as 230 and 345 GHz, will allow scientists to observe even finer details in quasars and other black holes.

“This discovery sheds new light on beam collimation in the quasar jets,” says Keiichi Asada, associate research fellow at the Academia Sinica, Institute of Astronomy and Astrophysics (ASIAA) in Taiwan. “The EHT’s sharper eyes will allow access to similar regions in more distant quasar jets. We hope to make progress on our new ‘homework’ from this study, which may allow us to finally answer the century-old problem of how jets are collimated.”

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

ALMA is a partnership of the 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 collaboration with the Republic of Chile. The Joint ALMA Observatory is operated by ESO, AUI/NRAO and NAOJ.

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

The VLBA is an instrument of the National Radio Astronomy Observatory, a US National Science Foundation facility operated by Associated Universities, Inc. under a collaborative agreement.

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