Low-metallicity starburst galaxies (blue compact dwarf galaxies – BCDs) provide a unique window in our understanding of galaxy formation and offer a unique opportunity to study galaxy formation under conditions approaching those of the first galaxies, prior to and during the epoch of reionization (EoR). Such galaxies contain rare massive stars, are likely to host superluminous supernovae (hypernovae), have “porous” ISM which enhances the escape of Ly and LyC radiation, and they enable studies of star formation and its feedback effects, including outflows and the enrichment of the IGM. In these respects, these galaxies are close analogues of the faint galaxies in high-z surveys, that dominate the star formation budget of the Universe at their epochs. A goal of this science case is to study intense starbursts in great detail, mapping the physical properties at a sub-kpc level, while encompassing the full extent of the target(s).
Figure 1: left: MUSE Hα map of the local starburst galaxy ESO338-IG04 with on the top right the derived velocity and velocity dispersion map (Bik et al. 2018). Bottom right: Blue and visual spectrum of the local starburst galaxy Pox 4 showing the rich emission line spectrum expected for BlueMUSE observations of such systems (López-Sánchez & Esteban 2009).
With BlueMUSE observations the following science goals can be addressed
- Determine the physical conditions in the interstellar medium of starburst galaxies by mapping multiple emission lines (e.g. Fig. 1)
- Quantify the interplay between the populations of massive stars (supernovae, stellar winds and ionising radiation) and their surroundings by deriving detailed gas kinematics and abundances. The BlueMUSE observations will allow us to detect the faint [OIII] auroral line at 4364Å, allowing us to constrain the temperature of the gas and derive the metallicity using the direct method.
- Determine the opacity to Lyman continuum and Lyman-radiation, through the ionisation state and density of the gas, in the analogue galaxies of those that reionised the Universe. The ratio of the [OIII] and [OII] fine structure lines is a direct tracer of the level of ionisation in the gas. Spatially resolved analysis of this ratio will reveal the presence of ionised channels where Lyman continuum radiation can escape.
- Study the assembly history of low-mass starburst galaxies in a spatially resolved manner