Scientists reach Back in Time to discover some of the most Power-packed Galaxies

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In the heart of an active galaxy, matter falling toward a supermassive black hole generates jets of particles traveling near the speed of light. Image Credit: NASA's Goddard Space Flight Center Scientific Visualization Studio

In the heart of an active galaxy, matter falling toward a supermassive black hole generates jets of particles traveling near the speed of light. Image Credit: NASA’s Goddard Space Flight Center Scientific Visualization Studio

When the universe was young, a supermassive black hole – bloated to the bursting point with stupendous power – heaved out a jet of particle-infused energy that raced through the vastness of space at nearly the speed of light. Billions of years later, a trio of Clemson University scientists, led by College of Science astrophysicist Marco Ajello, has identified this black hole and 4 others similar to it that range in age from 1.4 billion to 1.9 billion years old. These objects emit copious gamma rays, light of the highest energy, that are billions of times more energetic than light that is visible to the human eye.

The previously known earliest gamma-ray blazars – a type of galaxy whose intense emission is powered by extremely powerful relativistic jets launched by monstrous black holes – were more than 2 billion years old. Currently, the universe is estimated to be ~14 billion years old. “The discovery of these supermassive black holes, which launch jets that emit more energy in one second than our sun will produce in its entire lifetime, was the culmination of a yearlong research project,” said Ajello, who has spent much of his career studying the evolution of distant galaxies. “Our next step is to increase our understanding of the mechanisms involved in the formation, development and activities of these amazing objects, which are the most powerful accelerators in the universe. We can’t even come close to replicating such massive outputs of energy in our laboratories. The complexities we’re attempting to unravel seem almost as mysterious as the black holes themselves.”

The Clemson team’s breakthroughs were made possible by recently juiced-up software on NASA’s Fermi Gamma-ray Telescope. Using Fermi data, Ajello and Paliya began with a catalog of 1.4 million quasars, which are galaxies that harbor at their centers active supermassive black holes. Over the course of a year, they narrowed their search to 1,100 objects. Of these, 5 were finally determined to be newly discovered gamma-ray blazars that were the farthest away – and youngest – ever identified.

“We’re trying to understand the full spectrum of the energy distribution of these objects by using physical models,” Marcotulli said. “We are currently able to model what’s happening far more accurately than previously devised, and eventually we’ll be able to better understand what processes are occurring in the jets and which particles are radiating all the energy that we see. Are they electrons? Or protons? How are they interacting with surrounding photons? All these parameters are not fully understood right now. But every day we are deepening our understanding.”

All galaxies have black holes at their centers – some actively feeding on the matter surrounding them, others lying relatively dormant. Our own galaxy has at its center a super-sized black hole that is currently dormant. Only 1 of every 10 black holes in today’s universe are active. But when the universe was much younger, it was closer to a 50-50 ratio. The supermassive black holes at the center of the 5 newly discovered blazar galaxies are among the largest types of black holes ever observed, on the order of hundreds of thousands to billions of times the mass of our own sun. And their accompanying accretion disks emit more than 2 trillion times the energy output of our sun.

One of the most surprising elements of Ajello’s research is how quickly these supersized black holes must have grown in only 1.4 billion years. In terms of our current knowledge of how black holes grow, 1.4 billion years is barely enough time for a black hole to reach the mass of the ones discovered by Ajello’s team. “How did these incomprehensibly enormous and energy-laden black holes form so quickly?” Ajello said. “Is it because one black hole ate a lot all the time for a very long time? Or maybe because it bumped into other black holes and merged into one?

To be honest, we have no observations supporting either argument. There are mechanisms at work that we have yet to unravel. Puzzles that we have yet to solve. When we do eventually solve them, we will learn amazing things about how the universe was born, how it grew into what it has become, and what the distant future might hold as the universe continues to progress toward old age.”
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