Ara Pacis

2017-Feb-03, 07:18 PM

I'm not entirely sure what to think of this recent study published in Nature (http://www.nature.com/articles/s41550-016-0036) a few days ago. There's a less technical article and video illustrating the concept at IFLScience (http://www.iflscience.com/space/the-milky-way-is-running-away-from-an-extragalactic-void/all/). It models flow to the Shapley Attractor and concludes that there is a repeller that is pushing the local group.

I thought it was merely a statistical model from this wording:

When describing the gravitational dynamics in co-moving coordinates, by which the expansion of the Universe is factored out, underdensities repel and overdensities attract. The velocity field is represented here by means of streamlines (see Methods), the sources and sinks of which are the attractors and repellers of the large-scale structure

But some of the wording makes me think there's a physical object with repulsive properties:

We conclude that the dipole repeller is not a fictitious structure induced by an ‘edge of the data’ effect, and that subsets of the data, chosen either by distance or galaxy type, uncover a basin of repulsion that ‘pushes’ the Local Group in the direction pointed by the CMB dipole.

Thoughts?

I thought it was merely a statistical model from this wording:

When describing the gravitational dynamics in co-moving coordinates, by which the expansion of the Universe is factored out, underdensities repel and overdensities attract. The velocity field is represented here by means of streamlines (see Methods), the sources and sinks of which are the attractors and repellers of the large-scale structure

But some of the wording makes me think there's a physical object with repulsive properties:

We conclude that the dipole repeller is not a fictitious structure induced by an ‘edge of the data’ effect, and that subsets of the data, chosen either by distance or galaxy type, uncover a basin of repulsion that ‘pushes’ the Local Group in the direction pointed by the CMB dipole.

Thoughts?