Title: Formation of Polar Rings
Speaker: Hongsheng Zhao (University of St Andrews)
Time: 2:00PM, March 21 (Friday)
Location: 3rd floor, middle conf. room
Abstract: 
   We interpret the formation of the Local Group and its satellites in the context of interacting gas-rich galaxies.  Although enormous advances have been made in the techniques of N-body and hydrodynamic simulations for galaxy formation in recent years, we are unable to explain a number of important galaxy properties, e.g., the Baryonic Tully-Fisher relation and satellites of disk galaxies in phase-correlated ring-like giant structures, such as the baryonic lumps along the "Dentist-Chair” disk galaxy pair.  Polar rings of high M/L dwarf-galaxy satellites are often observed extragalactically and locally, but are almost impossible to form in a merger as tidal arms of the hypothesized CDM haloes, where baryonic cooling and collapse lead to satellites of normal M/L.  This leads Zhao, Famaey, Lughausen, Kroupa (A&A, 2013) to propose that such rings are evidences of frictionless fly-bys of disk galaxies in Modified Gravity theories, which naturally explain the high dynamical M/L of resulting satellites.  We examine how to check these competing arguments with future simulations.