A B S T R A C TWe present spectroscopic and polarimetric observations of a complete, optically unbiased sample of 2-Jy radio galaxies at intermediate redshifts ð0:15 , z , 0:7Þ. These data -which cover the nuclear regions of the target galaxies -allow us to quantify for the first time the various components that contribute to the UV excess in the population of powerful, intermediate-redshift radio galaxies. We find that, contrary to the results of previous surveys -which have tended to be biased towards the most luminous and spectacular objects in any redshift range -the contribution of scattered quasar light to the UV excess is relatively minor in most of the objects in our sample. Only seven objects (32 per cent of the complete sample) show significant polarization in the rest-frame UV, and none of the objects in our sample is polarized in the near-UV at the P . 10 per cent level. Careful measurement and modelling of our spectra have allowed us to quantify the contributions of other components to the UV excess. We show that nebular continuum (present in all objects at the 3 -40 per cent level), direct active galactic nucleus (AGN) light (significant in 40 per cent of objects) and young stellar populations (significant in 15 -50 per cent of objects) all make important contributions to the UV continuum in the population of powerful radio galaxies. These results serve to emphasize the multicomponent nature of the UV continuum in radio galaxies. The results also point to an interesting link between the optical/UV and far-IR properties of our sample objects, in the sense that the objects with the clearest evidence for optical/UV starburst activity are also the most luminous at far-IR wavelengths. This supports the idea that the cooler dust components in radio galaxies are heated by starbursts rather than by AGN.

We present high‐quality long‐slit spectra for three nearby powerful radio galaxies – 3C 293, 3C 305 and PKS 1345+12. These were taken with the aim of characterizing the young stellar populations (YSP), and thereby investigating the evolution of the host galaxies, as well as the events that triggered the activity. Isochrone spectral synthesis modelling of the wide wavelength coverage spectra of nuclear and off‐nuclear continuum‐emitting regions have been used to estimate the ages, masses and luminosities of the YSP component, taking full account of reddening effects and potential contamination by activity‐related components. We find that the YSP make a substantial contribution to the continuum flux in the off‐nuclear regions on a radial scale of 1–20 kpc in all three objects. Moreover, in two objects we find evidence for reddened post‐starburst stellar populations in the near‐nuclear regions of the host galaxies. The YSP are relatively old (0.1–2 Gyr), massive (109 < MYSP < 2 × 1010 M⊙) and make up a large proportion (∼1–50 per cent) of the total stellar mass in the regions of the galaxies sampled by the observations. Overall, these results are consistent with the idea that the nuclear activity of active galactic nuclei in some radio galaxies is triggered by major gas‐rich mergers. Therefore, these radio galaxies form part of the subset of early‐type galaxies that is evolving most rapidly in the local Universe. Intriguingly, the results also suggest that the radio jets are triggered relatively late in the merger sequence, and that there is an evolutionary link between radio galaxies and luminous/ultraluminous infrared galaxies.

A search for H i absorption has been made in 23 radio galaxies selected from a complete sample. The observations were made with the Australia Telescope Compact Array (ATCA), with the Very Large Array (VLA) and for one galaxy with the Westerbork Synthesis Radio Telescope (WSRT). In five galaxies H i absorption was detected. We investigate how the detection rate is distributed among galaxies with different radio and optical properties. Among the Fanaroff–Riley (FR) type I radio galaxies, only one object (10 per cent of the total) was detected in H i absorption. The H i absorption in these objects is likely to come from a nuclear disc, as found for other galaxies of this type (e.g. NGC 4261 and Hydra A). The low detection rate is consistent with the hypothesis (as suggested by optical and X‐ray data) that the ‘standard’ parsec‐scale, geometrically thick torus is not required in low‐luminosity radio galaxies. This is consistent with earlier optical work. In the case of FR type II powerful radio galaxies, no H i absorption has been detected in broad‐line radio galaxies, while three out of four narrow‐line radio galaxies have been detected (the one non‐detection having quite a high upper limit). All of these are compact or small radio galaxies. To first order this is consistent with the predictions of the unified schemes, assuming that the H i absorption is caused by an obscuring torus. However, the indications of this being the only cause of the absorption are not very strong. In particular, we find that in two of the three detected objects the H i is blueshifted compared with the systemic velocity. In the third galaxy (PKS 1549–79) two redshift systems (from the optical lines) are found. The uncertainty in the systemic velocity derived from optical lines is discussed. Finally, by also considering data available in the literature, we find a tendency for radio galaxies with a strong component of young stellar population and far‐infrared emission to show H i absorption. The overall richer interstellar medium that is likely to be present in these galaxies may be a factor in producing the absorption.

Observations of the starburst galaxy, M82, have been made with the VLA in its Aconfiguration at 15 GHz and MERLIN at 5 GHz enabling a spectral analysis of the compact radio structure on a scale of < 0.1 ′′ (1.6 pc). Crucial to these observations was the inclusion of the Pie Town VLBA antenna, which increased the resolution of the VLA observations by a factor of ∼2. A number of the weaker sources are shown to have thermal spectra and are identified as Hii regions with emission measures ∼10 7 cm −6 pc. Some of the sources appear to be optically thick at 5 GHz implying even higher emission measures of ∼10 8 cm −6 pc. The number of compact radio sources in M82 whose origin has been determined is now 46, of which 30 are supernova related and the remaining 16 are Hii regions. An additional 15 sources are noted, but have yet to be identified, meaning that the total number of compact sources in M82 is at least 61. Also, it is shown that the distribution of Hii regions is correlated with the large-scale ionised gas distribution, but is different from the distribution of supernova remnants. In addition, the brightest Hii region at (B1950) 09 h 51 m 42.21 s +69• 54′ 59.2 ′′ shows a spectral index gradient across its resolved structure which we attribute to the source becoming optically thick towards its centre.

A B S T R A C TWe present new spectroscopic observations of the southern radio galaxy PKS1549 2 79 ðz ¼ 0:152Þ. Despite the flat-spectrum character of the radio emission from this source, our optical spectra show no sign of the broad permitted lines and non-stellar continuum characteristic of quasar nuclei and broad-line radio galaxies. However, the high-ionization forbidden lines, including [O III]ll5007, 4959, are unusually broad for a narrow-line radio galaxy ðFWHM , 1350 km s 21 Þ, and are blueshifted by 600 km s 21 relative to the lowionization lines such as [O II]ll3726,3729. The [O II] lines are also considerably narrower ðFWHM , 650 kms 21 Þ than the [O III] lines, and have a redshift consistent with that of the recently detected H I 21-cm absorption-line system. Whereas the kinematics of the [O III] emission lines are consistent with outflow in an inner narrow-line region, the properties of the [O II] emission lines suggest that they are emitted by a more extended and quiescent gaseous component. We argue that, given the radio properties of the source, our line of sight is likely to be lying close to the direction of bulk outflow of the radio jets. In this case it is probable that the quasar nucleus is entirely obscured at optical wavelengths by the material responsible for the H I absorption-line system. The unusually broad [O III] emission lines suggest that the radio source is intrinsically compact. Overall, our data are consistent the idea that PKS1549 2 79 is a radio source in an early stage of evolution.