ICCUB Seminar. Ceclilia Mateu: “Predictions for the detection of Tidal Streams with Gaia using Great Circle Methods”

Although it is expected that Gaia will discover new stellar streams in the Galactic Halo, no estimates of how many dwarf galaxy streams are expected to be detected with Gaia were available to date.

I will present our work producing Milky Way Halo mock Gaia catalogues and using nGC3, a great-circle cell counts method to search for tidal streams using positional information and proper motions. Our eleven Galactic Halo mock catalogues were made from Milky-Way-mass haloes from the Aquarius and HYDRO-zoom cosmological simulations, and reproduce the Gaia selection function and observational errors for two stellar tracers: K giants and RR Lyrae stars.

The diversity of orbits and progenitors in the simulations allow us to characterize the nGC3 method’s completeness and detection limits in a realistic setting.

I will show the nGC3 method has a well-defined detection boundary, whose location can be predicted based on direct observables alone, and present predictions for the expected number of tidal streams to be detectable by Gaia+nGC3 with these two tracers. We will also analyse how different possible extensions of the Gaia mission will improve the detection of tidal streams.