The history of galaxies in the early Universe remains substantially unknown. The mystery surrounding these galaxies is in large part a result of the epoch in which they existed. During the epoch of reionization (z>5.5), the Universe experienced the last major phase change in cosmic time where the neutral gas permeating the intergalactic medium became ionized. Light emitted from early galaxies was often blocked by this neutral gas (or "cosmic fog"), preventing restframe UV spectroscopic studies of this epoch except for faint traces of light detectable in the NIR for the brightest sources. Prior to 2022, this high-redshift field was restricted due in large part to limited ground- and space-based instrumentation probing near-infrared wavelengths and beyond. During this time, much of what we learned spectroscopically about these galaxies came from a handful of bright UV metal emission lines or FIR emission (generally with only 1-2 lines detected in individual galaxies), data which only came from fighting for hours using the most massive telescopes on the ground and in space.
Since the advent of JWST, the high-redshift field has exploded with new science probing wavelengths and redshifts previously inaccessible. With the advanced spectroscopic NIR capabilities of the instrumentation on JWST, we have been able to find not only increasingly distant galaxies but to characterize sources that exist within the heart of the epoch of reionization. In this talk, we will discuss the state of the high-redshift field before and after the launch of JWST -- highlighting work from the Cosmic Evolution and Early Release Science (CEERS) survey, among other key ERS & Cy1 programs. Additionally, we will briefly discuss exciting future observations that can be or will be done using JWST for galaxies at these high redshifts, including showcasing the power of JWST IFU data in studying high-redshift analog galaxies with the TEMPLATES ERS survey.
Image Credit: NASA/STScI/CEERS/TACC/S. Finkelstein/M. Bagley/R. Larson/Z. Levay