FLEX (The First Light Explorer)—The Science Case for a Fully OH Suppressed IFU Spectrograph

The ability to achieve deep near infrared spectroscopy is of great importance to the future of astronomy. Our understanding of the early Universe depends on our ability to observe highly redshifted spectroscopic diagnostic features. Observations of H-α at wavelengths 0.9≤λ≤1.8 μm would allow accurate star-formation rates to be measured over the period 0.4≤z≤1.7—a crucial period in the formation of galaxies. Observations of Lyman-α at the same wavelengths would probe 6≤z≤13—the epoch at which the Universe underwent a major (and poorly understood) phase change from neutral to ionised. Similarly our understanding of low mass stars and unbound planets relies on NIR spectroscopy, since these objects emit most of their light at NIR wavelengths.