Abstract
We measure properties of dark matter in four well motivated scenarios: fermions with ultra-relativistic thermal equilibrium (URTE), bosons with URTE, fermions with non-relativistic thermal equilibrium (NRTE), and bosons with NRTE. We attempt to discriminate between these four scenarios with studies of spiral galaxy rotation curves, and galaxy stellar mass distributions. The measurements show evidence for boson dark matter with a significance of 3.5σ, and obtain no significant discrimination between URTE and NRTE.
Highlights
Non-relativistic dark matter in the early universe has a density ρh (a) that scales as a−3, and a particle root-mean-square velocity vhrms (a) that scales as a−1, where a is the expansion parameter. (Throughout, the sub-index “h”stands for the halo of dark matter.) Note that vhrms (a) ρh (a)1 3 is an adiabatic invariant independent of a
For bosons with ultra-relativistic thermal equilibrium (URTE) or non-relativistic thermal equilibrium (NRTE), there is a tail at large k due to the excess of low momentum dark matter particles in the limit μ′ → −0
We assume that dark matter is in thermal and diffusive equilibrium with the standard model sector in the early universe, and decouples while still ultra-relativistic
Summary
Non-relativistic dark matter in the early universe has a density ρh (a) that scales as a−3 , and a particle root-mean-square (rms) velocity vhrms (a) that scales as a−1 , where a is the expansion parameter. Stands for the halo of dark matter.) Note that vhrms (a) ρh (a) is an adiabatic invariant independent of a. Consider a free observer in a density peak. This observer feels no gravity, observes dark matter expanding adiabatically, reaching maximum expansion, and collapsing adiabatically into the core of a galaxy. Note that adiabatic expansion implies ( ) ( ) = vhrms a ( ) ( ) ( ) ρh a 1 3. Where 3 vr2h 1 2 is the root-mean-square velocity of dark matter particles in the core of the galaxy, and ρh (r → 0) is the density of dark matter in the core of the galaxy. (We use the standard notation in cosmology as defined in [1].)
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callMore From: International Journal of Astronomy and Astrophysics
Disclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
