8-12 juin, 2014


From Cusp To Core: Shedding Stellar Light on the Darkness of Matter

Aaron Maxwell (McMaster University)

James Wadsley, McMaster University Hugh Couchman, McMaster University Sergey Mashchenko, McMaster University Alison Sills, McMaster University

It has been well established that there exists a discrepancy between simple theoretical expectations and observations of dark matter profiles, especially those of dwarf galaxies. The resolution - vigorous star formation within the centres of dwarf galaxies leads to stellar feedback rapidly heating and re-distributing the dense star forming gas. Since this gas contributes significantly to the gravitational potential in dwarf galaxies, the peaked dark matter density expected from pure dark matter simulations can be quickly transformed to the flat density cores observed today. We showed that this core formation scenario can explain the observation of age and metallicity gradients in Local Group Dwarfs, and the formation and survival of dwarf galaxy globular clusters, a prominent example being Fornax. Our current work focuses on the multiple populations observed in most old Galactic globular clusters. If globular clusters form at the centres of dwarf galaxy progenitors, their orbits will steadily increase in accordance with the growth of the dark matter core. With each pass through the gas-rich centre of the dwarf, a globular cluster can accrete gas with varying light element abundances, evident in the multiple populations. We also use analytical arguments to show that star formation can indeed provide the energy to shape the dark matter structures within dwarf galaxies, contrary to recent work suggesting the cusp-core tension still exists.
(doit être confirmé par le SOC)