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Solving the Mystery of Weak Emission Line Quasars at High Redshift

by Ohad Shemmer (Dept. of Physics, University of North Texas, US)

Sep 19, 2013 from 02:00 PM to 04:30 PM

Where Seminars' room, floor -1, via Ranzani 1

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Abstract: Since strong and broad emission lines are a hallmark of quasar spectra, the recent discovery of luminous, high-redshift quasars with strong blue continua but extremely weak or undetectable emission lines is puzzling. I will present a step-by-step overview of multiwavelength observations that provided insights into the nature of these remarkable sources. In particular, I will show that the weakness of their emission lines is unlikely to be due to line absorption, dust obscuration, gravitational lensing or microlensing effects, or relativistic beaming. Finally, I will describe an observational and theoretical effort required to distinguish between several scenarios that have been proposed to explain the weakness of the emission lines in these sources. Solving the mystery about this rare class of quasars will shed light on emission-line formation and the accretion process in all active galactic nuclei.

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