Intrinsic redshift

Intrinsic redshift is the hypothesis from various non-standard cosmologies that a significant portion of the observed redshift of extragalactic objects (e.g. quasars and galaxies) may be caused by a phenomenon other than the traditionally accepted redshift mechanisms – (1) cosmological redshift; (2) Doppler redshift; and (3) gravitational redshift.

The main proponent of the intrinsic redshift hypothesis is astronomer Halton Arp, who noted that many of the astronomical radio sources close to radio galaxies were quasars — high redshift objects a minority of which are radio-loud. In some instances these quasars seemed aligned in pairs across the radio galaxies. Arp proposed the hypothesis that the quasars might be associated with the radio galaxies which themselves somehow ejected the quasars from the galactic nucleus. Quasars which followed this model are described as "local" and by extension their redshifts would not follow Hubble's law.

Since radio galaxies have much lower observed redshifts than the quasars, the excess quasar redshift could not have a Doppler origin from high ejection velocities because there are no blueshifted quasars with respect to the objects from which they are proposed to have originated. Since the traditionally accepted redshift mechanisms are not capable of explaining the large observed redshifts of quasars if they are associated with relatively nearby radio galaxies, Arp concluded that most of the observed redshift of the quasars must be caused by an unknown non-cosmological or "intrinsic" mechanism.

Other astronomers that have also published research supporting the hypothesis that at least some quasars are local rather than at cosmological distances include:

Geoffrey Burbidge who has been a long-time supporter of the local quasars hypothesis.
Morley Bell who studied the distribution of quasars around the Seyfert galaxy NGC 1068.
Lopez-Corredoira and Gutierrez who have studied the apparent association of higher redshift objects around NGC 7603 and the NEQ3 system.

Criticism

Arp's hypothesis that quasars are local and contain large intrinsic redshifts has never gained any significant support in the astronomy research community. Arp's work is based on a limited number of specific quasar-galaxy associations. Most astronomers believe these associations are simply the result of chance and point to the hundreds of thousands of quasars documented in more recent redshift surveys. These surveys show quasars to be distributed randomly over the sky, rather than associated with radio galaxies ^{[citation needed]}. Furthermore, there is now a detailed model of quasars as the ultraluminous cores of active galactic nuclei, effectively the centers of Seyfert galaxies. This model is consistent with the results of more sensitive observations which have been able to resolve host galaxies around quasars with the same redshift as the quasar. The consistency of the standard quasar model with the assumption that all quasars are at cosmological distances leads most astronomers to apply an Ockham's razor conclusion that intrinsic redshifts do not exist.

Arp still believes that quasars nevertheless have a high intrinsic redshift^[1]. To explain the fact that essentially all quasars are associated with host galaxies, he proposes that whatever results in the intrinsic redshift for the quasars also affects the redshift of the galaxy in the same way. He explains the angular size of the host galaxies, which is typical of that expected at cosmological distances, by proposing that the galaxies are ejected with the quasars from active galactic nuclei and only evolve into normal-sized galaxies over time, by a process different from the standard models of galaxy evolution.