Physics Colloquium: The Origins of Radio Emission from Radio-quiet Quasi-Stellar Objects (QSOs)

Thursday, February 28, 2019

3:30 PM-4:30 PM

Amy E. Kimball, PhD, National Radio Astronomy Observatory

Super-massive black holes are thought to power the extreme luminosity of all quasi-stellar objects (QSOs), but it is still not clear why only a small fraction of optically selected QSOs present as strong radio sources.

The radio emission from radio-loud QSOs (also known as quasars) originates in a jet from the active galactic nucleus (AGN) and its interactions with the surrounding medium. But for radio-quiet QSOs, recent results in the literature demonstrate an ongoing controversy. Using deep observations from the Very Large Array (VLA), we investigated the radio properties of a volume-limited sample of nearby QSOs. To determine radio properties of more distant QSOs, we applied a statistical analysis based on radio survey images.

While our results suggest radio emission from radio-quiet quasars is powered by host-galaxy star formation, other types of analysis lead to different conclusions. Other potential sources of radio emission include black hole spin, (scaled-down) AGN jets, and shocks from AGN driven winds. I will review what is understand about radio-loud and radio quiet AGNs, discuss the ongoing controversy, and present possible next steps.

Contact Information

Professor Gordon Richards
gtr@physics.drexel.edu