In article ,
Ray Tomes wrote:
Yes, of course there will be some. This can be calculated statistically
how many will fall within what distance. However I suggested the Monte
Carlo approach which is to compare to random datasets or moire simply
the same dataset rotated in space. If for 100 random rotations the
average associations within some range were say 40 with a maximum of 90
and the actual data had 250 associations then it would be very
convincing but if it were 85 then it would not.

Some test along these lines would certainly be one way to proceed.

However the really fascinating thing in Arp's data are the matched pairs
of quasars at similar redshifts (not identical and too far apart -
both proving it is not gravitational lensing) along opposite sides of
the axis of large nearby spirals.

Bear in mind that you expect to see (comparatively) widely separated
structures with similar redshifts in the standard model of big bang
structure formation. The question, again, is whether there's a
statistically significant excess of these associated with nearby
galaxies.

The Arp proposal does explain the very wide scatter in redshift versus
brightness of quasars compared to galaxies - because only part of the
redshift is considered to be cosmological. I don't think big bang
cosmology can explain this wide scatter.

Big bang cosmology doesn't need to -- this is just AGN physics. There
is a large scatter in the luminosities of AGN such as Seyferts and
low-luminosity radio galaxies at zero redshift, where presumably even
Arp doesn't think any new physics is happening. In the standard
picture, AGN luminosity is controlled by the black hole mass and
accretion rate, and it's entirely plausible that these differ widely
for different quasars at similar redshifts (in particular the
accretion rate depends on the very small scale environment of the
central black hole).

Martin
--
Martin Hardcastle Department of Physics, University of Bristol
A little learning is a dangerous thing; / Drink deep, or taste not the
Pierian spring; / There shallow draughts intoxicate the brain ...