What reionized the Universe?

Mon 13th May, 2019 @14:15 PM, level 6, David Caro Building
Dr Koki Kakiichi, University College London

Email: k.kakiichi@ucl.ac.uk


Study of reionization is now experiencing a surge of new insights, but the long-standing problem ‘what reionized the universe’ still remains unsolved. Hubble observations have placed a now-commonly-held view that the intrinsically faint galaxies are responsible for driving the reionization process, but with a fundamental assumption of large escape fractions >10%. A further puzzle comes from the recent deep spectroscopy of luminous galaxies and the spatial opacity fluctuation of the intergalactic medium (IGM) at z>5.7, which suggests a possibly important role of luminous systems and active galactic nuclei/quasars (QSOs). In the theoretical front, simulating early galaxies and the reionization process and is extremely challenging, requiring the understanding of the physics over a huge dynamic range from the scale of molecular clouds to the intergalactic medium. To shed light on these issues, we introduce a new spectroscopic programme surveying 56 QSO fields and a power of direct 3D mapping of galaxies and the IGM via 21cm tomography, which will be enabled by JWST, ELT, and SKA.