April 24, 2024

The short and bright lives of CSOs

Black hole jets concept art

Recent Caltech-led research has redefined Compact Symmetrical Objects (CSOs) as having short lifetimes, not because they are young, but because of their compact, short-lived jets driven by tidal disruption events, offering new insights into their cycle. of life and interactions with supermassives. black holes. Credit: SciTechDaily.com

Radio observations of Compact Symmetric Objects (CSOs) provide new clues about their origins.

A new investigation into an obscure class of galaxies known as Compact Symmetrical Objects, or CSOs, has revealed that these objects are not exactly what they seem. CSOs are active galaxies that host supermassive black holes in their cores. From these monstrous black holes emerge two jets traveling in opposite directions at almost the speed of light. But compared to other galaxies that have fierce jets, these jets don’t extend over great distances – they are much more compact. For many decades, astronomers suspected that CSOs were simply young and that their jets would eventually travel greater distances.

Now, reporting in three different articles on O Compact Symmetrical Object J1734+0926

This image, captured by the Very Long Baseline Array (VLBA), shows the Compact Symmetric Object (CSO) known as J1734+0926. The red bubbles are the ends of a powerful bipolar jet emanating from an invisible black hole. Credit: ML Lister/Purdue University

A distinct galactic phenomenon

“These CSOs are not young,” explains Anthony (Tony) Readhead, Robinson Professor Emeritus of Astronomy, who led the research. “You wouldn’t call a 12-year-old dog young, even though he lived a shorter lifespan than an adult human. These objects are distinct How compact symmetric objects are likely to form

This illustration shows how Compact Symmetric Objects, or CSOs, likely form. When a single massive star gets too close to a black hole (left), it is devoured. This causes the black hole to emit an ultrafast bipolar jet (center). The jet extends outward and its hot ends glow with radio emissions (right). Credit: B. Saxton/NRAO/AUI/NSF

The ephemeral life of CSOs

The team’s analysis concludes that CSOs expel jets for 5,000 years or less and then die. “CSO jets are very energetic jets, but they appear to shut down,” says Vikram Ravi, assistant professor of astronomy at Caltech and co-author of one of the studies. “The jets stop flowing from the fountain.”

As for what powers the short-lived jets, scientists believe the cause is a tidal disruption event (TDE), which occurs when a single star gets too close to a supermassive star. Very Long Baseline Array of Two Supermassive Black Holes

This image, taken by the Very Long Baseline Array (VLBA), shows two supermassive black holes, which appear as red-striped blobs. Black holes are at the center of an elliptical galaxy. The colors represent different spectral slopes in the radio emission, with red showing the denser regions around the black holes. The black hole on the right likely recently devoured a massive star, which caused it to launch two ultrafast jets. The ends of these jets appear as green spots above and below the black hole. This object, called J0405+3803, is referred to as a Compact Symmetric Object (CSO), because its jets are relatively close together (or compact), compared to other black holes with much larger jets. Credit: HL Maness/Grinnell College

Tidal disruption events: empowering CSOs

“We think that a single star is torn apart and then all that energy is channeled into jets along the axis around which the black hole rotates,” says Readhead. “The giant black hole starts out invisible to us, and when it consumes a star, boom! The black hole has fuel and we can see it.”

Cosmic objects called Compact Symmetrical Objects (CSOs) likely form when a single massive star comes too close to a supermassive black hole and is ripped apart. The process, highlighted in this animation, results in violent bipolar jets that last up to 5,000 years. Credit: B. Saxton/NRAO/AUI/NSF

Readhead first suspected that CSOs could be powered by TDEs in the 1990s, but says the idea went largely unnoticed by the scientific community. “The hypothesis was largely forgotten because it was years before observational evidence began to mount for TDEs,” he says. At the time of his original hypothesis, only three CSOs had been found.

Rediscovering and Defining CSOs

Fast forward to 2020. Readhead, who interrupted his studies on OSCs to delve deeper into different problems in radio astronomy, decided it was time to revisit the topic. He gathered some of his colleagues on Zoom and they decided to scour the literature and eliminate objects that had been misclassified as OSCs. Over the next two years, the team investigated more than 3,000 CSO candidates, narrowing the group down to just dozens who met the criteria to be real CSO.

Ultimately, a picture began to emerge of CSOs as an entirely distinct family, with jets that die long before their gigantic brethren, such as those in the extremely powerful Cygnus A, a galaxy that emits extremely powerful jets that shine brightly at lengths of radio wave. . These jets extend for distances of about 230,000 light-years in each direction and last for tens of millions of years. In contrast, CSO jets extend out to about 1,500 light-years at most and disappear in about 5,000 years.

Tony Readhead

Tony Readhead. Credit: Caltech

A new path for galactic study

According to astronomers, CSO jets likely form when a supermassive black hole approaches not just any star, but a substantial star.

“The TDEs we saw previously only lasted a few years,” says Ravi. “We think that the remarkable TDEs that power CSOs last much longer because the perturbed stars are either very large in size, very massive, or both.”

By analyzing the CSO’s varied collection of radio images, researchers say they can track how objects age over time, almost like looking at a photo album of a CSO’s life to observe how their jets evolve. Younger CSOs have shorter jets that are closer to the black holes, while older objects have jets that extend further away from the black hole. Although most jets die, scientists estimate that one in 100 will be as long-lived as those in Cygnus A. In these rare cases, the galaxies are likely merging with other galaxies, a turbulent process that provides a large amount of fuel.

If Readhead and his team’s findings are confirmed with additional observations, CSOs will provide an entirely new way to study how massive stars at the centers of galaxies interact with supermassive black holes.

“These objects are in fact a distinct population with their own distinct origin, and it is up to us now to learn more about them and how they came to be,” says Readhead. “Being able to study these objects on timescales of years to decades, rather than millions of years, has opened the door to an entirely new laboratory for studying supermassive black holes and the many unexpected and unpredictable surprises they hold.”

The three studies are, “Compact Symmetric Objects – I Towards a Comprehensive and Bona Fide Catalog”, “Compact Symmetric Objects – II Confirmation of a Distinct Population of Active Galaxies with High Luminosity Jets” and “Compact Symmetric Objects – III Evolution of High-brightness range and a possible connection to tidal disruption events.”


“Compact Symmetrical Objects. I. Towards a Comprehensive and Genuine Catalog” by S. Kiehlmann, ML Lister, AC S Readhead, I. Liodakis, Sandra O’Neill, TJ Pearson, Evan Sheldahl, Aneta Siemiginowska, K. Tassis, GB Taylor and PN Wilkinson, 31 January 2024, The Astrophysical Journal.
DOI: 10.3847/1538-4357/ad0c56

“Compact Symmetrical Objects. II. Confirmation of a distinct population of active galaxies with high-luminosity jets” by S. Kiehlmann, ACS Readhead, S. O’Neill, PN Wilkinson, ML Lister, I. Liodakis, S. Bruzewski, V. Pavlidou, TJ Pearson, E .Sheldahl, A. Siemiginowska, K. Tassis, and G. B. Taylor, January 31, 2024, The Astrophysical Journal.
DOI: 10.3847/1538-4357/ad0cc2

“Compact Symmetrical Objects. III. Evolution of the high-luminosity branch and a possible connection to tidal disruption events” by AC S Readhead, V. Ravi, RD Blandford, AG Sullivan, J. Somalwar, MC Begelman, M. Birkinshaw, I. Liodakis, ML Lister, TJ Pearson, GB Taylor, PN Wilkinson, N. Globus, S. Kiehlmann, CR Lawrence, D. Murphy, S. O’Neill, V. Pavlidou, E. Sheldahl, A. Siemiginowska and K. Tassis, January 31, 2024, The Astrophysical Journal.
DOI: 10.3847/1538-4357/ad0c55

The studies were funded by the NSF,

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