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Probing First Light With Quasar Spectroscopy

Dr Emma Ryan-Weber

Centre for Astrophysics and Supercomputing, Swinburne University of Technology

3:30 pm Friday, 2 July 2010,
EN413 (EN Building), Hawthorn.

The details surrounding the end of the dark ages are among the final unknowns in modern astronomy. We have yet to discover when the starlight from the first galaxies lit up the Universe, ionizing the surround neutral hydrogen gas. I will talk about our search for intergalactic carbon at the highest observable redshifts. The close link between the ionizing flux from stars and the elements they produce allows us to make a measurement of the number of ionizing photons emitted in the early Universe, completely independent of the difficult detection of individual galaxies at redshifts greater than 6. We find that massive stars (as we know them) can't quite provide enough ionizing photons to reionize cosmic hydrogen. I will discuss possible solutions to this puzzle, including evidence from near-IR spectroscopy of distant quasars to measure the ionization state of the intergalactic medium at the conclusion of the dark ages, 1 billion years after the big bang.

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