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We present a catalogue of 261 new infrared selected members of the 3C 129 galaxy cluster. The cluster, located at z ≈ 0.02, forms part of the Perseus-Pisces filament and is obscured at optical wavelengths due to its location in the zone of avoidance. We identified these galaxies using the J- and K-band imaging data provided by the UKIDSS Galactic Plane Survey within an area with a radius of 1.1° centred on the X-ray emission of the cluster at ℓ, b ≈ 160.52° ,0.27°. A total of 26 of the identified galaxy members have known redshifts 24 of which are from our 2016 Westerbork H I survey and two are from optical spectroscopy. An analysis of the galaxy density at the core of the 3C 129 cluster shows it to be less dense than the Coma and Norma clusters, but comparable to the galaxy density in the core of the Perseus cluster. From an assessment of the spatial and velocity distributions of the 3C 129 cluster galaxies that have redshifts, we derived a velocity of cz = 5227 ± 171 km s−1 and σ = 1097 ± 252 km s−1 for the main cluster, with a substructure in the cluster outskirts at cz = 6923 ± 71 km s−1 with σ = 422 ± 100 km s−1. The presence of this substructure is consistent with previous claims based on the X-ray analysis that the cluster is not yet virialised and may have undergone a recent merger. [ABSTRACT FROM AUTHOR]

We present results of a blind 21cm HI-line imaging survey of a galaxy overdensity located behind the Milky Way at ℓ, b≈ 160°, 0.5°. The overdensity corresponds to a zone-of-avoidance crossing of the Perseus-Pisces Supercluster filament. Although it is known that this filament contains an X-ray galaxy cluster (3C 129) hosting two strong radio galaxies, little is known about galaxies associated with this potentially rich cluster because of the high Galactic dust extinction. We mapped a sky area of ∼9.6 deg2 using the Westerbork Synthesis Radio Telescope in a hexagonal mosaic of 35 pointings observed for 12 h each, in the radial velocity range cz = 2400-16 600 km s-1. The survey has a sensitivity of 0.36 mJy beam-1 rms at a velocity resolution of 16.5 km s-1.We detected 211 galaxies, 62 per cent of which have a near-infrared counterpart in the UKIDSS Galactic Plane Survey. We present a catalogue of the HI properties and an HI atlas containing total intensity maps, position-velocity diagrams, global HI profiles and UKIDSS counterpart images. For the resolved galaxies we also present HI velocity fields and radial HI surface density profiles. A brief analysis of the structures outlined by these galaxies finds that 87 of them lie at the distance of the Perseus-Pisces Supercluster (cz ∼ 4000-8000 km s-1) and seem to form part of the 3C 129 cluster. Further 72 detections trace an overdensity at a velocity of cz ≈ 10 000 km s-1 and seem to coincide with a structure predicted from mass density reconstructions in the first 2MASS Redshift Survey. [ABSTRACT FROM AUTHOR]