134 Are the QSO's really at their redshift distances?
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This article is from the Astronomy FAQ, by Joseph Lazio (jlazio@patriot.net) with numerous contributions by others.
134 Are the QSO's really at their redshift distances?
By Martin Hardcastle <m.hardcastle@bristol.ac.uk>
It's often suggested that QSOs are not at the distances that would be
inferred from their redshifts and from Hubble's law; this would avoid
the enormous powers and necessity for general-relativistic physics in
the standard model. Many arguments of this type are flawed by a lack
of consideration of the other types of galaxies and active galactic
nuclei (AGN): unless it's believed that _no_ galaxy is at its redshift
distance, i.e., that the whole concept of redshift is wrong, then we
know that there are objects very similar to QSOs which _are_ at their
redshift distances. (Cosmological theories that overthrow the whole
idea of redshift and the big bang are beyond the scope of this
discussion, although several have been proposed based on the apparent
spatial association of objects with very different redshifts.)
Another argument favoring QSOs being at their redshift distance comes
from gravitational lensing. Gravitational lenses occur when two
objects are nearly aligned, and the mass of the foreground object
lenses (magnifies and/or distorts) the background object. In every
gravitational lens for which redshifts are known, the galaxy (or
galaxies) acting as the lens has a lower redshift than the galaxy
being lensed.
A recent analysis of data available from the 2-degree field (2dF
survey) also showed no evidence for a connection between galaxies and
QSOs. This analysis is particularly significant because the people
who carried out the analysis spoke to proponents on both sides of the
argument *before* conducting their analysis (Hawkins, Maddox, &
Merrifield 2002, Mon. Not. R. Astron. Soc., vol. 336, p. L13).
More generally, though, like many arguments in science, this one also
has an element of aesthetics. The proponents of the standard model
argue that the physics we know (general relativity, special
relativity, electromagnetism) is sufficient to explain QSOs, and that,
by Occam's razor, no model introducing new physics is necessary. Its
opponents argue either that there are features of QSOs which cannot be
explained by the standard model or that the predictions of the
standard model (and, in particular, its reliance on supermassive black
holes) are so absurd as clearly to require some new physics. A good
deal of bad science has been put forward (on both sides) on sci.astro.
Readers should be aware that the scientific community isn't as
insanely conservative as some posters would have them believe, and
that a number of other possibilities for QSO physics were considered
and rejected when they were first discovered. For example, the
frequent suggestion that the redshifts of QSOs are gravitational does
not work in any simple model. Species having different ionization
potentials ought to exist at different distances from the central
source and thus should have different redshifts, but in fact emission
lines from all species are observed to have the same redshift.
For examples of claims of galaxy-QSO associations, see papers by
Stockton, either of the Burbidges, or Arp. For additional, technical
discussions of why these conclusions are not valid, see papers by
Newman & Terzian; Newman, Terzian, & Haynes; and Hawkins, Maddox, &
Merrifield (2002).
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