Abstract
The presence of enhanced ultraviolet (UV) emission in early-type galaxies, which are dominated by old stellar populations, has been a puzzle for more than 40 years. The observed UV flux plausibly contains contributions from both evolved stars (traditionally referred to as the 'UV upturn' phenomenon) and young stars. While the UV upturn is well-characterised observationally, a firm understanding of its origin still eludes us. Similarly, while recent results from GALEX and deep optical surveys strongly indicate the presence of small mass fractions of young stars across low and intermediate redshift, the exact mechanism (e.g. stellar mass loss, minor mergers) that drives this star formation is not fully understood. The role of active galactic nuclei in regulating the low-level star formation at late epochs also remains relatively unexplored in galaxy formation models.
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