Adithya Balasubramaniam

The tale of two streams separated by an ocean

Stellar streams – formed through the tidal disruptions of dwarf galaxies and star clusters –can tell us about the nature of their progenitors as well as the distribution of mass inside their orbits. The Southern Stream Stellar Spectroscopic Survey (S5) employs the Anglo-Australian Telescope (AAT) to study stellar streams, using photometric and proper-motion data to identify candidate member stars and AAOmega spectra to obtain radial velocities and abundance information. Work done by S5 has explored stream membership, orbit models and progenitors in detail. S5 also takes high resolution follow-up spectra for confirmed stream members to analyze their detailed properties and better understand the evolutionary histories of progenitor dwarf galaxies and globular clusters. I will present an in-depth study and comparison of two metal-poor, distant stellar streams originally identified in the Dark Energy Survey: Elqui and Turranburra – the latter named after Sydney’s Lane Cove River. Both dwarf galaxy streams are rather distant, with Elqui at a Galactocentric distance of 52 kpc and Turranburra at 28 kpc. In previous work, both streams have been found to have high velocity dispersions and low mean metallicities, implying that their progenitors were relatively low-mass dwarf galaxies.Through studying the dynamics and properties of these two streams, we are increasing our understanding of the accretion history of the Milky Way, as well shedding light on the broader processes that shape galaxy formation in general.