Giant Emission Line Nebulae Around QSOs

Monday, 09 September 2013 9 a.m. — 10 a.m. MST

AURA Lecture Hall

NOIRLab South Colloquia
FABRIZIO ARRIGONI (Max Planck Institute, Heidelberg and Gemini South Visiting Astronomer)

Giant (100 kpc) and luminous Lyman-alpha nebulae are observed at high redshift around high-redshift radio galaxies (HZRGs), QSOs, and in a population known as Lyman-alpha blob (LABs). There is a growing body of evidence that all of these phenomenon are somehow related. In the first part of this talk I'll show the preliminary striking results of an ongoing Lyman-alpha survey targeting QSOs at z about 2 with the Keck/LRIS and Gemini-South/GMOS instruments. We have discovered two objects which exhibit unprecedentedly large (~ 500 physical kpc) Ly-alpha emission nebulae extending to the scale of the cosmic web. In the second part of the talk, I'll present the results of a deep (20hr integrations) narrow-band imaging program with the VLT/FORS2 instrument targeting the HeII (1640A) and the CIV (1549) lines for 13 LABs in a single overdense field. The goal of this study is to obtain sensitive line flux constraints for emission lines besides Ly-alpha, providing additional diagnostics to help distinguish between the different physical mechanisms that could power these objects. I will show our results, summarize previous detections in the literature, and present the results of simple photoionization models which can help us understand these observations.