The Discovery of A Large Population of Obscured AGN in Disguise as Low Luminosity AGN in Chandra Deep Field South

Erini Lambrides
Johns Hopkins University
Tuesday, October 27, 2020
2:00 pm
Zoom Seminar
Abstract: Population synthesis models of actively accreting supermassive black holes (or active galactic nuclei -- AGN) predict a large fraction that must grow behind dense, obscuring screens of gas and dust. Deep X-ray surveys are thought to have provided the most complete and unbiased samples of AGN, but there is strong observational evidence that a portion of the population of obscured AGN is being missed. In this talk, I will highlight results from my recent work on where we use a sample of AGN derived from the deepest X-ray survey to date, the Chandra 7Ms GOODS-South Survey, to investigate the nature of low flux X-ray sources.  We maximize the diverse wavelength coverage of the GOODS-South field, and cross-match our objects with wavelengths from the Radio to the IR. We find the predicted column densities are on average an order of magnitude higher than the calculated column densities via X-ray detections for X-ray faint sources. We interpret our results as evidence of obscured AGN disguising as low-luminosity AGN via their X-ray luminosities. The discovery of these objects has deep implications for future X-ray surveys and X-ray AGN selection criteria. I will also touch on our current work of using this unique sample to probe long standing problems with popular SMBH-Galaxy Co-Evolution paradigms.  
Arianna Long