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Dying of the Light: Cold Quasars & The Shutdown of Galaxy Growth

Presentation #109.04 in the session “AGN and Quasars 1”.

Published onJan 11, 2021
Dying of the Light: Cold Quasars & The Shutdown of Galaxy Growth

To understand how massive galaxies came to be, we must understand how their star formation rich pasts are affected due to non-stellar processes such as the supermassive black holes in the hearts of galaxies. When a supermassive black hole actively accretes interstellar gas, the surrounding material becomes luminous across the electromagnetic spectrum and is visible as an object called an active galactic nucleus (AGN), or a quasar in the most luminous cases. This energetic output has a tremendous effect on the host galaxy, warming the gas in a process called AGN feedback. AGN feedback is a model commonly cited as the method that a star-forming, gas-rich galaxy transitions to a non-star-forming, gas-poor galaxy. To address how AGN affect their host’s star formation, I will present results from a recently uncovered subtype of quasar, called ‘cold quasars’. These galaxies host a luminous AGN at their hearts but still retain a cold gas component which we can detect in the far-infrared. These galaxies are observed in the rare moment when an AGN is active but has yet to finish excavating the cold gas from the host, continuing to host star formation rates of ~100s of solar masses per year, hundreds of times more active than our own Milky Way Galaxy. I present new results using a cold quasar detected using the SOFIA far-infrared telescope. Using this new data from SOFIA along with optical observations using the Sloan Digital Sky Survey and additional infrared data from the Spitzer and Herschel space telescopes, we fit a collection of stellar and black hole models to the data. Using these fits, we discuss the importance of cold quasars toward the understanding of these rare and energetic galaxies.


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