Galaxies that refused to recede: Halton Arp and intrinsic redshift
Halton Arp photographed quasars and galaxies that appeared physically connected despite sharply different redshifts, challenging the use of redshift as distance alone.
Arp created the influential Atlas of Peculiar Galaxies and published extensive observations of apparent galaxy-quasar associations.
Most astronomers interpret these alignments within standard cosmology rather than as evidence of intrinsic quasar redshift.
A catalogue of peculiar galaxies
Arp's observational atlas documented distorted, interacting and unusual galaxies. Some fields showed high-redshift objects unusually close to lower-redshift active galaxies.
What redshift usually means
Cosmic expansion stretches light and makes redshift a key distance indicator. Arp proposed that young ejected matter could carry an additional intrinsic component.
He emphasized quasars paired across active nuclei, X-ray sources and apparent luminous bridges, reading them as related systems rather than chance projections.
The dispute asks whether a general law should absorb exceptional images or whether the exceptions should revise the law. Arp's photographs remain the heart of the story.