J0317+769: presents a peculiar morphology consisting of a core and two FR I type symmetric and prominent jets, which end in two FR II type lobes (better seen in the 4.9 GHz map). From the SW lobe, a faint and extended tail rises directed in S direction (1.4 GHz map). This tail is completely resolved out in our 4.9 GHz map.
J0455+603: a peculiar radio source with a well defined core embedded in a low brightness halo-like structure in NW-SE direction. Our 1.4 GHz map shows marginal evidence of a jet in NW direction. No redshift information is available for this radio source.
J0508+609: a low power FR I type giant radio galaxy with a prominent flat spectrum core and two opposite jets directed in SE-NW direction. Both jets present large opening angles. The northern jet can be followed at larger distances from the core than the southern one, which is resolved out beyond 1.25 ′ from the core in our map at 1.4 GHz, but clearly seen in the NVSS map up to 6 ′ from the core. At 4.9 GHz we only detect the core component, a 13 ′′ jet in SE direction and marginal evidence of the counter-jet on the opposite side.
J0525+718: a low power radio galaxy with two symmetric jets in the E-W direction. The western jet shows a 90○ bend in projection towards the north. It is not clear if this bend is somehow related to a compact source seen in the same field. The total flux density of J0525+718 at 1.4 GHz is below the 100 mJy limit after the subtraction of the flux density from this compact source, but we have kept it in the final sample. At 4.9 GHz we only detect a weak core component and a very faint jet and counter-jet emission (map not shown).
J0531+677: our 4.9 GHz map shows a weak core and two symmetric jets in the NE-SW direction, typical of an FR I structure. What is peculiar in this radio source is the existence of a very faint and extended tail directed towards the south, similar to that previously described in J0317+769. A similar tail might be present in the other jet as in wide angle tail radio galaxies, but the emission quickly fades below the noise level. It is the nearest object in the sample, at z=0.017.
J0546+633: an asymmetric FR I type radio galaxy with a NE-SW orientation. The jet and counter-jet are prominent in our maps and well collimated. While the SW jet fades away as it separates from the core, the NE jet is shorter and presents a strong bending backwards. This is another example of a radio galaxy with an asymmetric structure, possibly resulting from different degrees of interaction of the oppositely directed jets with the external medium and/or the projection effects.
J0607+612: a radio galaxy with lobes in the NE-SW direction. Its projected linear size is 1.47 Mpc (GRG). At 4.9 GHz we can clearly follow the jet directed towards the NE lobe. The structure of J0607+612 cannot be easily classified as an FR I or FR II type.
J0624+630: a low power FR I radio source oriented in N-S direction with an S-shaped morphology. The N-jet presents a strong bend at 0.7 ′ from the core. The core component is clearly identified in the 4.9 GHz map.
J0654+733: a 2 Mpc long FR II radio galaxy directed in the NE-SW direction, with prominent hotspots at the lobe extremes. The core is displaced towards the SW with respect to the center of symmetry of the source. A background compact source, most probably unrelated, is located close to the northern lobe.
0750+656: the most distant object of our sample, at z=0.747. It is a GRG with a linear projected size of 1.8 Mpc. It presents a prominent core and a FR II type radio structure in NW-SE direction.
J0807+740: a giant low-power radio galaxy. At 1.4 GHz, this peculiar radio source presents a compact core component and a weak and extended halo-like emission elongated in the E-W direction. There is no evidence of jets or hotspots in our maps. At 4.9 GHz we only detect the core component. This object could be a relic FR II radio galaxy, where hotspot regions are no more present and extended lobes are still detected at 1.4 GHz.
J0819+756: an FR II type GRG (linear size of 2.2 Mpc) oriented in NE-SW direction. It presents a strong inverted spectrum core ( α1.44.9=0.5; Flux density ∝να). Both lobes harbour a double hotspot structure at their extremes. The source beyond the NE lobe is an unrelated background object, as suggested by its structure and its optical identification.
J1015+683: presents a very complex and distorted structure oriented in the E-W direction resembling, mostly at 4.9 GHz, two double radio galaxies closely seen in projection, one slightly above the other. This is supported by the optical image which shows two nearby galaxies in the field identifed with radio components (Paper II). Redshift and core data in Table 2 refer to the northern feature.
J1137+613: a symmetric radio galaxy of FR II type morphology with prominent hotspots at the end of the lobes. There is evidence of a strong backflow from both radio lobes which is deflected in opposite directions perpendicularly to the axis defined by the jets.
J1211+743: a GRG (linear size of 1.2 Mpc) which presents a peculiar structure, not clearly discriminated between FR I or II types. There is a prominent jet in the NW direction, showing blobs of emission and a bent structure. A faint counter-jet is also detected. No strong hotspots are observed in the lobes.
J1247+673: a known Gigahertz Peaked Spectrum radio galaxy with a FR II type morphology (de Vries et al. 1997A&A...321..105D), also a member of the class of giant radio galaxies (linear size of 1.94 Mpc). It clearly contrasts with respect to the rest of the sample in its core dominance (67% of the source emission at 1.4 GHz comes from the core, which is the only feature detected at 4.9 GHz).
J1251+787: one of the most extended radio galaxies in our sample (19.5 ′ ; redshift is not available for this source). It presents a FR I type morphology, with two irregular S-shaped and well collimated jets. They present several blobs of emission and bends until they fall below the noise level of our images.
J1313+696 (4C+69.15): an FR II type radio galaxy oriented in SE-NW direction. With a projected linear size of 1.06 Mpc, it belongs to the class of giants. At 1.4 GHz the emission from the lobes form a continuous bridge along the entire source. At 4.9 GHz only the core and the lobe extremes are detected. This case emphasizes the importance of the observations made at 4.9 GHz to distinguish the core component, needed to identify the associated galaxy.
J1504+689 (4C+69.18): one of the few quasars in the sample, presents a typical FR II type morphology with a bright flat-spectrum core and two lobes with prominent hotspots. With a projected linear size of 1.16 Mpc, it is a giant radio quasar. There is an unrelated strong compact source at 2.16′ from the core, in SW direction, which was misidentified with a component of J1504+689 by Reid et al. (1995A&AS..110..213R).
J1557+706 (4C+70.19): it presents an FR I type morphology in the N-S direction. The northern jet bends by 180○ towards the south, becoming diffuse and extended beyond the bend. The southern jet ends in an extended lobe-like region. At 4.9 GHz we only detect a compact core and the beginning of two rather symmetric jets, separated from the core by symmetric gaps.
J1632+825 (NGC 6251): a very well studied radio galaxy (e.g. Perley et al. 1984ApJS...54..291P), and the most extended one in our sample (66 ′ ≡2.54 Mpc). Our observations show only a prominent and well collimated one-sided jet in the NW direction, with no evidence of the counter-jet emission. Total angular size and total flux density in Table 2 are from Perley et al. (1984ApJS...54..291P).
J1650+815: a peculiar low brightness asymmetric radio galaxy. The core is clearly identified at 4.9 GHz, and appears displaced towards the north with respect to the center of the radio structure. There is evidence of a jet departing from the core in S-SW direction, and two extended and diffuse lobes.
J1732+714: an FR I type radio galaxy with two symmetric jets departing from a central core. The jets end in two extended lobes without strong hotspots. It presents a bridge of low brightness emission southward of the jets and in the same direction, very much like the relic emission observed in 3C338 (Giovannini et al. 1998ApJ...493..632G).
J1745+712 (4C+71.17): at 1.4 GHz it shows an FR II type morphology in the E-W direction with a dominant bright emission from the core region. Higher resolution observations at 4.9 GHz show a small and prominent structure (∼ 15′′ ) with a core and a two symmetric jet components, which might be the result of an episode of enhanced activity, as in the case of J1835+620 (Lara et al. 1999A&A...348..699L).
J1751+680: a wide angle tail radio source with detached lobes displaced towards the east. The southern jet presents a sharp bend of ∼ 90○. An unrelated double radio source appears confused with the southern lobe when observed at low angular resolution (e.g. in the NVSS map).
J1754+626 (NGC 6512): another wide angle tail source, with an extension of low brightness emission in the southern direction. The radio structure is very complex, with sharp bends and kinks, most likely produced by the interaction with the external medium. At 4.9 GHz we observe the core component and two jets in the E-W direction. The eastern jet bends sharply towards the west, most probably due to the existence of a strong intergalactic wind.
J1918+742: a GRG with projected linear size of 1.64 Mpc. It presents an FR II type morphology in the E-W direction, with the core strongly displaced towards the east from the center of symmetry of the source. At 4.9 GHz we only detect the core and the hotspot in the western lobe.
J2035+680: an FR I type radio galaxy in the N-S direction with two extended and diffuse lobes. The northern jet presents a prominent blob of emission at 2′ from the core. The angular size is 11.5′ , which correspond to 2.14 Mpc in projected linear size for a redshift z=0.133 (uncertain). There is a strong and compact radio source almost superposed to the southern lobe, which we consider unrelated to J2035+680.
J2111+630: a peculiar source with an FR II type morphology in the NW-SE direction. At 1.4 GHz, the lobes appear extended with signs of backflow, but there are not prominent hotspots. At 4.9 GHz we only detect a weak core (flux density ∼1 mJy). We could not determine the redshift of the associated galaxy.
J2114+820: presents an FR I type structure, with S-shaped extended lobes and a strong and variable flat spectrum core (variability observed in our data at different epochs). There is a prominent jet in the NW direction with several blobs of emission and with a very strong widening at about ∼ 20′′ from the core. A weaker counter-jet is observed on the opposite side. Its optical spectrum presents prominent broad emission lines (Stickel et al. 1993A&AS...97..483S; Paper II), which according with current unification schemes of radio loud Active Galactic Nuclei (e.g. Urry & Padovani 1995PASP..107..803U), is in contradiction to its classification as an FR I radio galaxy (see also Lara et al. 1999A&A...348..699L).
J2138+831: a strongly asymmetric radio galaxy in the cluster Abell 2387. While the eastern lobe bends southwards forming a long tail of FR I type, the western lobe resembles those found in FR II type radio sources. At 4.9 GHz we observe how the jet directed towards the west loses its collimation at ∼ 30′′ from the core.
J2145+819: an FR II type radio galaxy with a N-S orientation. It is the intrinsically largest radio galaxy in our sample (a giant among the giants, with a projected linear size of 3.74 Mpc). The northern lobe presents an almost perfect conical shape with a prominent hotspot at its extreme (see Lara et al. 2000A&A...356...63L). Palma et al. (2000AJ....119.2068P) present a detailed study of this radio source.
J2157+664 (4C 66.24): a very peculiar and asymmetric radio source. At first sight (1.4 GHz observations) it seems to have two typical radio lobes in the E-W direction, one of them with a strong hotspot. However, observations at 4.9 GHz and spectral index considerations show that the core is hosted by the western "lobe'', and that a jet directed towards the west interacts at a very short distance from the core with the external medium, producing a very strong bow-shock. On the opposite side, there is a long jet which seems to bend in an almost closed loop, forming a long tail of low brightness emission towards the south (observed at 1.4 GHz).
J2209+727: an FR II type radio galaxy in the NW-SE direction. The core is very weak and appears confused with the lobe emission at 1.4 GHz. At 4.9 GHz we can clearly identify the weak core (flux density 400 µJy) and the hotspots at the extremes of the lobes. There are two nearby radio sources in the same field, most probably unrelated with J2209+727.
J2340+621: a peculiar radio source extended in the E-W direction, with two collimated S-shaped jets. In both jets there are prominent blobs of emission at ∼ 22′′ (E-jet) and ∼ 30′′ (W-jet) from the core, which suggest different phases in the core activity, as in the case of J1745+712 or J1835+620 (Lara et al. 1999A&A...348..699L). This radio source is located at a very low galactic latitude, 0.4○. We detected its optical counterpart, although its extragalactic nature could not be confirmed (Paper II).