We study the kinematic properties of the ionised gas outflows and ambient interstellar medium (ISM) in a large and representative sample of local luminous and ultra-luminous infrared galaxies (U/LIRGs) (58 systems, 75 galaxies) at galactic and sub-galactic (i.e., star-forming clumps) scales, thanks to integral field spectroscopy (IFS)-based high signal-to-noise integrated spectra. The velocity dispersion of the ionized ISM in U/LIRGs ( σ ∼ 70 km s −1 ) is larger than in lower luminosity local star-forming galaxies ( σ ∼ 25 km s −1 ). While for isolated disc LIRGs star formation appears to sustain turbulence, gravitational energy release associated with interactions and mergers plays an important role in driving σ in the U/LIRG range. We find that σ has a dependency on the star formation rate density (Σ SFR ), which is weaker than expected if it were driven by the energy released by the starburst. The relatively small role of star formation (SF) driving the σ in U/LIRGs is reinforced by the lack of an increase in σ associated with high luminosity SF clumps. We also find that the impact of an active galactic nucleus (AGN) in ULIRGs is strong, increasing on average σ by a factor 1.5. Low-z U/LIRGs cover a range of velocity dispersion (σ ∼ 30 to 100 km s −1 ) and star formation rate density (Σ SFR ∼ 0.1 to 20 M yr −1 kpc −2 ) similar to those of high-z SFGs. Moreover, the observed weak dependency of σ on Σ SFR for local U/LIRGs (σ ∝ Σ +0.06 SFR ) is in very good agreement with that measured in some high-z samples. The presence of ionized gas outflows in U/LIRGs seems universal based on the detection of a broad, usually blueshifted, Hα line. The observed dependency of the maximum velocity of the outflow (V max ) on the star formation rate (SFR) is of the type+0.24 . We find that AGNs in U/LIRGs are able to generate faster (∼×2) and more massive (∼× 1.4) ionized gas outflows than pure starbursts. The derived ionized mass loading factors (η) are in general below 1, with only a few AGNs above this limit. The escaping gas fraction is low with only less massive (log(M dyn /M ) < 10.4) U/LIRGs having outflowing terminal velocities higher than their escape velocities, and more massive galaxies retaining the gas, even if they host an AGN. The observed average outflow properties in U/LIRGs are similar to high-z galaxies of comparable SFR. However, while high-z galaxies seem to require Σ SFR > 1 M yrfor launching strong outflows, this threshold is not observed in low-z U/LIRGs even after correcting for the differential fraction of the gas content. In the bright SF clumps found in LIRGs, ionized gas outflows appear to be very common (detection rate over 80%). Their observed properties are less extreme than those associated with the entire galaxy. The clumps in LIRGs follow the general size-L-σ scaling relations found for low-and high-z clumps, though they are in general smaller, less luminous, and are characterized by lower σ than at high-z. For a given observed (no internal extinction correction applied) star formation...

Abstract. In classifying the ensemble of powerful extragalactic radio sources, considerable evidence has accumulated that radio galaxies and quasars are orientation-dependent manifestations of the same parent population: massive spheroidal galaxies containing correspondingly massive black holes. One of the key factors in establishing this unification has been the signature of a hidden quasar detected in some radio galaxies in polarized light. The obscuration of our direct view of the active nucleus usually, but not necessarily exclusively, by a thick nuclear disk or torus can act conveniently as a "natural coronograph" that allows a much clearer view of the host of a radio galaxy than of a quasar. In this study, we exploit the opportunity to eliminate the quasar glare by performing sensitive spectropolarimetry with the Keck II telescope of a sample of radio galaxies with redshifts around 2.5. This represents the epoch when quasars were many times more common that they are now and is likely to be the period during which their host galaxies were being assembled into what become the most massive galaxies in the Universe today. We show that dust-reflected quasar light generally dominates the restframe ultraviolet continuum of these sources and that a highly clumped scattering medium results in almost grey scattering of the active galactic nucleus photons. The observations, however, do not exclude a substantial star formation rate averaged over a Gyr of evolution. The sub-mm reradiation from the scattering dust is likely to represent only a small fraction (∼10%) of the total far infrared luminosity. An analysis of the emission lines excited in the interstellar medium of the host galaxy by the hard quasar radiation field reveals evidence of a dramatic chemical evolution within the spheroid during this epoch. Secondary nitrogen production in intermediate mass stars produces a characteristic signature in the Nv/Civ and Nv/Heii line ratios which has been seen previously in the broad line region of quasars at similar redshifts. We find intriguing correlations between the strengths of the Lyα and Nv emission lines and the degree of ultraviolet continuum polarization which may represent the dispersal of dust associated with the chemical enrichment of the spheroid.

A B S T R A C TThe nature of the optical-radio correlations for powerful radio galaxies is investigated using spectroscopic observations of a complete sample of southern 2-Jy radio sources. In line with previous work, we find that significant correlations exist between the luminosities of the [O III]l5007, [O II]l3727 and Hb emission lines and the radio luminosity. However, our observations are not easily reconciled with the idea that these correlations are caused by the increase in the power of the photoionizing quasar as the jet power increases, with average ISM properties not changing appreciably with redshift or radio power: not only do we find that the scatter in the L ½O iiiÿ versus L radio correlation is significantly larger than in L ½O iiÿ versus L radio and L Hb versus L radio correlations, but the ionization state deduced from the emission lines does not increase with radio power as predicted by the simple, constant ISM, photoionization model. We conclude that (a) there exists a considerable range in the quasar ionizing luminosity at a given redshift, and (b) the mean density of the emission-line clouds is larger in the highredshift/high-power radio sources. The latter density enhancement may be either a consequence of the increased importance of jet-cloud interactions or, alternatively, the result of a higher pressure in the confining hot ISM, in the high-redshift objects.Apart from the general scatter in the correlations, we identify a distinct group of objects with [O III]l5007 luminosities which are more than an order of magnitude lower than in the general population radio galaxies at similar redshift. These weak-line radio galaxies (WLRGs) are likely to be sources in which the central ionizing quasars are particularly feeble.Deep spectra show that many of the sources in our sample are broad-line radio galaxies (BLRGs). The fact that the BLRGs are observed out to the redshift limit of the survey, overlapping in redshift with the quasars, argues against the idea that BLRGs are simply the low-radio-power counterparts of high-power, high-redshift quasars. Either there exists a considerable range in the intrinsic luminosities of the broad-line AGN for a given redshift or radio power, or the BLRGs represent partially obscured quasars. The degree of scatter present in the L ½O iiiÿ versus L radio correlation supports the former possibility.

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.

The Lynx arc, with a redshift of 3.357, was discovered during spectroscopic follow-up of the z ¼ 0:570 cluster RX J0848+4456 from the ROSAT Deep Cluster Survey. The arc is characterized by a very red RÀK color and strong, narrow emission lines. Analysis of HST WFPC2 imaging and Keck optical and infrared spectroscopy shows that the arc is an H ii galaxy magnified by a factor of $10 by a complex cluster environment. The high intrinsic luminosity, the emission-line spectrum, the absorption components seen in Ly and C iv, and the rest-frame ultraviolet continuum are all consistent with a simple H ii region model containing $10 6 hot O stars. The best-fit parameters for this model imply a very hot ionizing continuum (T BB ' 80; 000 K), a high ionization parameter (log U ' À1), and a low nebular metallicity (Z=Z ' 0:05). The narrowness of the emission lines requires a low mass-to-light ratio for the ionizing stars, suggestive of an extremely low metallicity stellar cluster. The apparent overabundance of silicon in the nebula could indicate enrichment by past pair-instability supernovae, requiring stars more massive than $140 M .

We present long‐slit near‐infrared (NIR) spectra, obtained using the Infrared Spectrometer And Array Camera (ISAAC) instrument at the Very Large Telescope, which sample the rest‐frame optical emission lines from nine radio galaxies at z∼ 2.5. One‐dimensional spectra have been extracted and, using broad‐band photometry, have been cross‐calibrated with spectra from the literature to produce line spectra spanning a rest wavelength of ∼1200–7000  Å. The resulting line spectra have a spectral coverage that is unprecedented for radio galaxies at any redshift. We have also produced a composite of the rest‐frame ultraviolet (UV)–optical line fluxes of powerful, z∼ 2.5 radio galaxies. We have investigated the relative strengths of Lyα, Hβ, Hα, He  iiλ1640 and He  iiλ4687, and we find that Av can vary significantly from object to object. In addition, we have identified new line ratios to calculate electron temperature: [Ne v]λ1575/[Ne v]λ3426, [Ne  iv]λ1602/[Ne  iv]λ2423, O  iii]λ1663/[O  iii]λ5008 and [O  ii]λ2471/[O  ii]λ3728. We calculate an average O  iii temperature of 14100+1000−600 K. We have modelled the rich emission line spectra, and we conclude that they are best explained by active galactic nucleus (AGN) photoionization with the ionization parameter U varying between objects. For shock models (with or without the precursor) to provide a satisfactory explanation for the data, an additional source of ionizing photons is required – presumably the ionizing radiation field of the AGN. Single slab photoionization models are unable to reproduce the high‐ and the low‐ionization lines simultaneously: the higher ionization lines imply higher U than do the lower ionization lines. This problem may be alleviated either by combining two or more single slab photoionization models with different U, or by using mixed‐medium models such as those of Binette, Wilson & Storchi‐Bergmann. In either case, U must vary from object to object. On the basis of N v/N  iv] and N  iv]/C  iv we argue that, while photoionization is the dominant ionization mechanism in the extended emission line regions (EELR), shocks make a fractional contribution (∼10 per cent) to its ionization. The N v/N  iv] and N  iv]/C  iv ratios in the broad‐line region (BLR) of some quasars suggest that shock ionization may be important in the BLR also. We find that in the EELR of z∼ 2 radio galaxies the N/H abundance ratio is close to its solar value. We conclude that N/H and metallicity do not vary by more than a factor of 2 in our sample. These results are consistent with the idea that the massive ellipticals which become the hosts to powerful AGN are assembled very early in the history of the universe, and then evolve relatively passively up to the present day.

We present the final band‐merged European Large‐Area ISO Survey (ELAIS) Catalogue at 6.7, 15, 90 and 175 μm, and the associated data at U, g′, r′, i′, Z, J, H, K and 20 cm. The origin of the survey, infrared and radio observations, data‐reduction and optical identifications are briefly reviewed, and a summary of the area covered and the completeness limit for each infrared band is given. A detailed discussion of the band‐merging and optical association strategy is given. The total Catalogue consists of 3762 sources. 23 per cent of the 15‐μm sources and 75 per cent of the 6.7‐μm sources are stars. For extragalactic sources observed in three or more infrared bands, colour–colour diagrams are presented and discussed in terms of the contributing infrared populations. Spectral energy distributions (SEDs) are shown for selected sources and compared with cirrus, M82 and Arp220 starburst, and active galactic nuclei (AGN) dust torus models. Spectroscopic redshifts are tabulated, where available. For the N1 and N2 areas, the Isaac Newton Telescope ugriz Wide Field Survey permits photometric redshifts to be estimated for galaxies and quasars. These agree well with the spectroscopic redshifts, within the uncertainty of the photometric method [∼10 per cent in (1 +z) for galaxies]. The redshift distribution is given for selected ELAIS bands and colour–redshift diagrams are discussed. There is a high proportion of ultraluminous infrared galaxies (log10 of 1–1000 μm luminosity Lir > 12.22) in the ELAIS Catalogue (14 per cent of 15‐μm galaxies with known z), many with Arp220‐like SEDs. 10 per cent of the 15‐μm sources are genuine optically blank fields to r′= 24: these must have very high infrared‐to‐optical ratios and probably have z > 0.6, so are high‐luminosity dusty starbursts or Type 2 AGN. Nine hyperluminous infrared galaxies (Lir > 13.22) and nine extremely red objects (EROs) (r−K > 6) are found in the survey. The latter are interpreted as ultraluminous dusty infrared galaxies at z∼ 1. The large numbers of ultraluminous galaxies imply very strong evolution in the star formation rate between z= 0 and 1. There is also a surprisingly large population of luminous (Lir > 11.5), cool (cirrus‐type SEDs) galaxies, with Lir−Lopt > 0, implying AV > 1.

About 54 per cent of radio galaxies at z 3 and 8 per cent of radio galaxies at 2 z < 3 show unusually strong Lyα emission, compared with the general population of high-redshift (z 2) radio galaxies. These Lyα-excess objects (LAEs) show Lyα/He II values consistent with or above standard photoionization model predictions.We reject with confidence several scenarios to explain the unusual strength of Lyα in these objects: shocks, low nebular metallicities, high gas densities and absorption/scattering effects. We show that the most successful explanation is the presence of a young stellar population which provides the extra supply of ionizing photons required to explain the Lyα excess in at least the most extreme LAEs (probably in all of them). This interpretation is strongly supported by the tentative trend found by other authors for z 3 radio galaxies to show lower ultraviolet rest-frame polarization levels, or the dramatic increase in the detection rate at submm wavelengths of z > 2.5 radio galaxies. The enhanced star formation activity in LAEs could be a consequence of a recent merger which has triggered both the star formation and the active galactic nucleus/radio activities.The measurement of unusually high Lyα ratios in the extended gas of some high-redshift radio galaxies suggests that star formation activity occurs in spatial scales of tens of kpc.We argue that, although the fraction of LAEs may be incompletely determined, both at 2 z < 3 and at z 3, the much larger fraction of LAEs found at z 3 is a genuine redshift evolution and not due to selection effects. Therefore, our results suggest that the radio galaxy phenomenon is more often associated with a massive starburst at z > 3 than at z < 3.