Defining the frame of minimum nonlinear Hubble expansion variation

Understand

We characterize a cosmic rest frame in which the monopole variation of the spherically averaged nonlinear Hubble expansion is most uniform, under arbitrary local Lorentz boosts of the central observer.

• Using the COMPOSITE sample of 4534 galaxies, we identify a degenerate set of candidate minimum nonlinear variation frames, which includes the rest frame of the Local Group (LG) of galaxies, but excludes the standard Cosmic Microwave Background (CMB) frame.
• Candidate rest frames defined by a boost from the LG frame close to the plane of the galaxy have a statistical likelihood similar to the LG frame.
• This may result from a lack of constraining data in the Zone of Avoidance.