15 November 2001 CfA Colloquium


Title: z~6 Quasars from the SDSS: Probing the Reionization Epoch

Speaker: Xiaohui Fan

Abstract:

I will present the discoveries of four luminous quasars at 5.7 < z < 6.3 using the data from the Sloan Digital Sky Survey. The density of quasars declines exponentially toward high redshift. The existence of strong metal emission lines in the quasar spectra indicates early chemical enrichment in the quasar environment. We use high S/N Keck and VLT spectroscopy to study the evolution of ionizing background at high redshift, and the process of cosmic reionization. The ionizing background declines by a factor of >20 from z=3 to z=6. The first detection of a complete Gunn-Peterson trough in the spectrum of the highest redshift quasar at z=6.28 indicates that the IGM is quickly approaching neutrality at this redshift. By comparing with simulations of cosmological reionization we show that z~6 marks the end of the reionziation epoch.

References for students:

Fan et al. astro-ph/0108063

Becker et al. astro-ph/0108097

Gnedin 2000, ApJ, 535, 530

Lunch with the students will be on Friday, November 16 at 12:00 in A-101.