Black holes are a critical part of the formation and evolution of galaxies and new radio telescopes will be needed for us to learn how black holes interact with stars and galaxies.
Dr. Kristina Nyland was a postdoctoral research associate at the National Radio Astronomy Observatory. She described the current incomplete understanding of black holes and why they are important and the new technology that will enable us to understand them.
A black hole is a massive, compact object whose gravity is so strong that not even light can escape. The most massive black holes, which have masses of millions to billions of solar-masses, are known as supermassive black holes and are believed to have formed in the early universe and reside in the centers of most galaxies. When a supermassive black hole is in the process of accreting material, this is called an “active galactic nucleus” – or AGN. As they actively consume material, AGN emit electromagnetic radiation at many wavelengths, making it possible to detect their presence and study their properties. At radio wavelengths, this radiation typically takes the form of powerful “jets” of radio plasma, which are formed by high-speed particles spiraling around the magnetic field of the supermassive black hole.
As the most energetic, long-lived objects in the universe, AGN are able to dramatically alter their surroundings. Powerful radio jets are able to heat cold gas (raw star formation material) negating its ability to efficiently form new stars, or – in the most extreme cases – completely expel the gas out of the host galaxy. The transfer of energy from an AGN into the surrounding interstellar or intergalactic gas is known as “AGN feedback.” AGN feedback is believed to be an important process in shaping galactic stellar populations as galaxies form and grow over billions of years. It is not understood how AGN feedback impacts galaxy evolution as a function of key galaxy properties such as mass and distance.
Next Radio Telescope Proposed for 2030s
Astronomers are imagining the next generation Very Large Array (ngVLA) with 244, 59-foot (18-meter) dishes spread over 5,505 miles (8,860 km). The Very Large Array (VLA) was built in the 1970s with an array of 27 82-foot (25-meter) dishes arranged in a “Y” shape.
Next generation radio telescope arrays would have a ten-fold improvement in sensitivity compared to the VLA, as well as a 30X improvement in angular resolution, the ngVLA will enable large statistical studies of AGN feedback in action. The ngVLA will be able to image the dominant population of AGN, which typically host radio jets with sub-galactic extents, over a large cosmic volume.
The ngVLA will also operate over a much wider range of frequencies (1 to 116 GHz) compared to the VLA (1 to 50 GHz), it will also be able to capture information from the carbon monoxide molecule, which has a bright transition around 115 GHz. This molecule can be used to measure the content and conditions of a galaxy’s star-forming gas reservoir.
The ngVLA will directly measure the effects of radio-jet-driven AGN feedback on galaxy evolution by comparing the radio jet and cold gas properties in galaxies over a wide variety of galaxy masses, distances, and environments. The new information will be compared with large computer simulations and improve our understanding of black hole physics and the universe.
SOURCE – National Radio Astronomy Observatory
Written By Brian Wang