Unravelling the Neutrino Mass Hierarchy with Cosmological Observations

Event Sponsor: 
Argonne Leadership Computing Facility Seminar
Start Date: 
Sep 29 2015 - 10:30am
Building 240/Room 4301
Argonne National Laboratory
Jeffrey D. Emberson
Speaker(s) Title: 
Graduate Student Researcher, Canadian Institute for Theoretical Astrophysics
Tim Williams

Neutrinos occur in great abundance throughout the Universe, yet remain poorly understood due to their weak interaction with other matter. In particular, individual neutrino masses remain an elusive property for particle physicists and cosmologists abound. Recently, it has been proposed that individual neutrino mass may be constrained from a unique dipole distortion induced by the relative flow between cold dark matter (CDM) and neutrinos. This has the potential of being observed using galaxy surveys, with the only information required being knowledge of the CDM-neutrino relative velocity. Since neither CDM nor neutrinos are directly observable, their relative velocity must be derived by other means. We modify the cosmology code, CUBEP3M, to simulate neutrino N-body particles alongside CDM.

In this talk, we show that the relative velocity field can be accurately reconstructed using linear transformations on the halo density field. This provides compelling support for constraining individual neutrino mass from upcoming observations. To test the observational prospects of this effect, we recently completed another simulation, named TianNu (the “Neutrino Sky”). TianNu contains 3 trillion neutrino plus CDM particles and was performed on over 330,000 cores of the Tianhe-2 supercomputer. We present preliminary results from TianNu on the observational imprint of cosmic neutrinos.