Double white dwarfs: the most prolific Galactic source of gravitational waves

The discovery of gravitational waves from merging black holes and neutron stars heralds an explosion of opportunity to understand the landscape of the remnants of stellar and binary evolution. LISA, a future space-based gravitational wave detector, will provide access to the millihertz band of the gravitational wave spectrum that is complementary to gravitational waves observed by LIGO. At these lower frequencies, Galactic double white dwarfs will dominate LISA source counts by several orders of magnitude with tens of thousands of individually resolved systems and millions of systems contributing to a gravitational wave foreground. In this talk I will review our current understanding of double white dwarf populations discovered through EM surveys and present recent results which predict the population of double white dwarfs that LISA may observe. In particular, I will focus on the effects of the recently observed anti-correlation in binary fraction with metallicity for solar type stars on the Galactic double white dwarf population.