Exploring Galaxy Formation in the First Billion Years
In the past 5 years our ability to probe the very-high redshift Universe has been dramatically transformed, thanks largely to installation of Wide Field Camera 3 on the Hubble Space Telescope. As of early 2015 we have now identified around 1000 candidate star forming galaxies at z~7 and above, with the first, albeit small, samples now emerging at z~10.
By combining Hubble observations with those of other facilities such as the Spitzer, Herschel, and now the Atacama Large Millimetre Array (ALMA) we can begin to constrain a range of physical properties including intrinsic star formation rates, stellar masses, dust masses, and ionising escape fraction. These in turn can be used to infer the star formation rate density, stellar mass density, and the ionising photon luminosity density. Critically, this latter quantity allows us determine whether typical star forming galaxies were responsible for reionisation or whether something more exotic was required. More generally though, the determination of these physical properties allows us to test and subsequently refine galaxy formation models during a critical epoch of the Universe’s history.