Title:  Solving the Mystery of Weak Emission Line Quasars at High Redshift

Dr. Ohad Shemmer
UNT

Abstract:

Since strong and broad emission lines are a hallmark of quasar UV spectra, the recent discovery of ~80 Sloan Digital Sky Survey quasars at z~2.2-5.9 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 two competing scenarios for the weakness of the emission lines in these sources. The results of this study will likely shed light not only on the nature of this rare class of quasars but also on emission-line formation in all active galactic nuclei.