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Center for Astrophysics Research and Technologies Seminar Series Information

 

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Radio emission from radio-"quiet" QSOs: star formation or AGN?

Thursday November 10, 2016
2:00 pm


 Presenter:  Amy Kimball, NRAO
 Series:  Center for Astrophysics Research and Technologies Seminar Series
 Abstract:  Despite decades of study and continuing recent controversy, it is still unclear whether there are distinct radio-loud and radio-quiet populations of quasi-stellar objects (QSOs). I present results from the Karl G Jansky Very Large Array whose sensitivity allowed us to obtain nearly complete radio detections of a volume-limited QSO sample in the redshift range 0.2 < z < 0.3; these observations constitute the first (and to date the only) full characterization of the QSO radio luminosity distribution from a volume-complete optically selected QSO sample. We detected sources as faint as log(L_6GHz) ~ 10^21 Lsun, well below the radio luminosity that separates star-forming galaxies from radio-loud active galactic nuclei (AGNs) driven by accretion onto a super-massive black hole. Extrapolation of the previously known radio-AGN luminosity function to low luminosities predicted that most QSOs should be extremely radio-quiet, but our results show this not to be the case. The radio luminosity function of QSOs may be explained by a combination of two radio emission components, with AGN emission dominating the bright end and starbursting host galaxies dominating the faint end. We confirmed this result statistically using a much larger sample of low-signal-to-noise survey images. Our conclusion remains controversial, but could be tested using sub-millimeter observations with ALMA, or high-resolution VLBI imaging to look for the presence of AGN-jet structure.
 Location:  PAIS-2540, PAIS

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