Orateur
Description
LISA is a space mission to observe millihertz gravitational waves (GWs), planned for 2035. Millions of white dwarf binaries in the Milky Way (MW) will contribute to LISA data, of which a few thousand are expected to be individually resolved. The unresolved signal, dubbed the Galactic foreground, can be astrophysically interpreted through careful analysis. We assess LISA's capability to separate the MW bulge and disk foreground components. We generate mock catalogues of Galactic binaries (GBs) in the MW, using axisymmetric density templates while varying total mass and mass ratio. For each catalogue, we simulate the LISA foreground through an iterative technique. We then use the BLIP pipeline to fit the signal to a Whittle likelihood model, characterizing the data as colored Gaussian noise of parametrized spectral shape, with known nonstationarities induced by the GW source anisotropy. We show that the bulge and disk signals can be distinguished. From a simple model where their spectra differ only in amplitude, we are able to measure total Galactic binary population mass within 2% and the bulge/disk ratio within 8%, matching the precision of photometric and kinematic data. Our work demonstrates that resolving MW structure is feasible in a LISA Global Fit, providing complementary information to electromagnetic observations.