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This is the first in a series of papers discussing the properties of a complete set of radio sources selected near {ital S}{sub 408}=1 Jy. We present optical or infrared identifications for a sample of 452 radio galaxies. The sources were selected from the 408 MHz Molonglo Reference Catalog, restricted only by flux density and position on the sky, as follows: {ital S}{sub 408}{ge}0.95 Jy and {minus}30{degree}{lt}decl. (1950){lt}{minus}20{degree}, and 9{sup h}20{sup m}{lt}R.A.(1950){lt}14{sup h}4{sup m} or 20{sup h}20{sup m}{lt}R.A.(1950){lt}6{sup h}14{sup m}. This complete sample, the MRC/1 Jy survey, contains 558 radio galaxies or quasars, of which six are occulted by bright stars or galaxies and two are multiple confused sources. Of the remaining 550 sources, 527, or 96{percent}, are identified to an {ital r} magnitude of 25, and eight additional sources are identified to {ital K}=19. Of the 17 unocculted objects that remain unidentified, 15 are sources for which we have either poor radio maps or inadequate optical/IR images. This paper presents finding charts and astrometric positions for the 452 sources that are not identified as either quasars or BL Lacertae objects. Magnitudes in the {ital r} passband accurate to typically 0.1 mag are given for 353 of the radio galaxymore » identifications. Redshifts for 268 of the galaxies are also listed; these have been derived from 450 spectroscopic observations. The radio observations, quasar and BL Lac identifications, spectroscopy, and near-IR images will be presented in subsequent papers in this series. {copyright} {ital 1996 The American Astronomical Society.}« less

We report the discovery of a blue, star-forming region in the eastern lobe of the nearby (z=0.0794), classical double-lobed radio galaxy 3C 285. This region is elongated along the radio source axis, and its optical line emission, and possibly its optical continuum emission, appear to be edge-brightened on the side facing the nucleus of 3C 285. We propose that the star formation in this region was triggered by the passage of the radio lobe through a region of dense gas in the intergalactic medium. Our observations add support to models in which powerful radio sources induce star formation through the compression of dense ambient material and are also in agreement with such an interpretation for the alignment effect observed in high-redshift radio galaxies

3C 364 has many of the credentials of a luminous radio galaxy at very high redshift: faint optical magnitude (m R =22), ultrasteep radio spectrum (α=1.29), and apparent multimodal galaxy morphology associated with (but nearly perpendicular to) a small (2″) double radio source. However, our spectroscopy shows it to be at a relatively modest redshift of z=0.917. Its spectrum is dominated by a red stellar continuum and strong [O II] emission. The infrared magnitude of 3C 364 is K=17.27, typical for 3CR and 1 Jy-class radio galaxies at z∼0.9.

We present photometric and spectroscopic observations of SN 1991bg, a very peculiar Type Ia supernova located in the outskirts of the E1 galaxy NGC 4374 (M84) in the Virgo cluster. At maximum brightness SN 1991bg was 1.6 mag subluminous in V and 2.5 mag subluminous in B, compared with normal SNe Ia. The colors were unusually red, but the object was not significantly reddened by dust. The decline from maximum was certainly quite steep; we measure an initial linear V fading of 0.10 mag/d rather than the typical value of 0.06 mag/d for SNe Ia, and a late-time decline of 0.034 mag/d rather than 0.026 mag/d

VLA radio observations and optical imaging and spectroscopy of the Einstein radio ring 0218+357 are presented. The ring is detected at 22.4 GHz and shows a basically similar structure at 5, 15, and 22.4 GHz. The B component has varied and was about 15 percent brighter in the 8.4 GHz data than in the data of Patnaik et al. (1992). The ring is highly polarized. A weak jetlike feature extending out roughly 2 arcsec to the southeast of component A is detected at 6 cm. The source has amorphous radio structure extending out to about 11 arcsec from the core. For an adopted redshift of 0.68, the extended radio emission is very powerful. The optical spectrum is rather red and shows no strong features. A redshift of about 0.68 is obtained. The identification is a faint compact m(r) about 20 galaxy which extends to about 4.5 arcsec (about 27 kpc). As much as 50 percent of the total light may be due to a central AGN. The observed double core and ring may be produced by an off-center radio core with extended radio structure.

The spatial distributions of thermal emission-line gas and nonthermal radio-emitting plasma in powerful radio galaxies are examined. At high redshifts and luminosities, the thermal gas is distributed very asymmetrically with respect to the galaxy nucleus. The one-sidedness of the emission line regions is clear evidence of an intrinsically asymmetric property of powerful radio sources. The radio sources are more asymmetric in their lobe spacings at high redshifts, but not at a highly significant level

U and B continuum and Ly-alpha images obtained with the UV-flooded TI2 CCD at the prime focus of the 4-m telescope at KPNO during May and November 1988 are reported for 19 radio-loud high-redshift QSOs. The data are presented in extensive contour maps, radial surface-brightness profiles, and tables and discussed in detail. Ly-alpha emission with typical luminosity about 10 to the 44th erg/sec and spatial extent about 100 kpc is spatially resolved in 15 QSOs, and these nebulae are attributed to the photoionization of the interstellar or intergalactic medium of young or proto galaxies by radiation escaping anisotropically along the radio axis of the QSO. The mechanisms possibly responsible for the Ly-alpha emission and for the UV fuzz seen around some of the QSOs are explored. 84 refs.

Using the Video Camera (e.g. Butcher et al. 1980) and the High Gain Video Spectrometer (e.g. Heckman et al. 1981) we are carrying out a program at Kitt Peak to search for optical line emission associated with the jets and lobes of radio galaxies. Several sources have been found in which extended optical line emission is clearly related to the nonthermal radio emission. Some general information on these and a few other sources is summarized in Table 1.

Quite naturally so, VLBI'ers tend to be somewhat far-sighted: because of the very high resolutions, and poor UV-coverages, obtained with current VLBI networks only distant objects can be suitably studied. Unfortunately one thus tends to oversee some basic properties of a very popular class of objects, namely the compact, steep-spectrum radio cores. I would like to put these objects in their proper perspective.

Powerful radio galaxies are unique at the present time in that they have optically resolvable structures that can observed over a range of look-back times comparable to the Hubble time. This allows us to examine how their morphologies evolve with cosmic time in their stellar continuum, thermal line-emitting gas, and non-thermal synchrotron emitting plasmas. The continuum shapes of high redshift radio galaxies become more elongated at high redshift and are closely aligned with their radio source axes. The extended emission line regions were larger and more luminous in the past and they too are well aligned with their radio source axes. Finally, the radio sources themselves were more asymmetric in the past both in terms of their structures and in the flux densities, spectral indices and polarization of the diffuse lobes.

Here I shall interpret ‘small-scale’ to mean a few kpc or less. Such jets occur over a wide range of emitted energies (e.g. 1039∈rg s-1 in M87, 1046 in 3C273) and we do not know if they are manifestations of the same basic phenomenon or whether Nature is fooling us in some way despite the morphological similarities. For the moment, it seems sensible to asume an underlying unity and to use the observations to explore the jet phenomenon in different guises.

Optical and radio observations of nearby and distant powerful radio galaxies with extended optical emission-line regions are discussed. Comparisons of optical emission-line images with radio continuum maps, supplemented with detailed optical spectroscopy, show that the interaction of radio jets and lobes with ambient gas can have dramatic consequences for both the radio source and its surrounding medium. We will discuss evidence for the occurence of large scale star formation and collimated ionizing radiation along the axes of radio galaxies. We also present preliminary results indicative of large rotation measures in two distant radio galaxies.

Optical and radio observations of nearby and distant powerful radio galaxies with extended optical emission-line regions are reviewed. Comparisons of optical emission-line images with radio continuum maps, supplemented with detailed optical spectroscopy, show that the interaction of radio jets and hot spots with ambient gas can have dramatic consequences for both the radio source and its surrounding medium. I will discuss evidence for the deflection and decollimation of (low power) jets, gas entrainment by jets and hot spots, Faraday depolarization/rotation near regions of dense ionized gas, enhanced star formation along radio source trajectories, and collimated ionizing radiation from radio galaxy nuclei.

High resolution longslit spectra have been used to study the dynamical, physical, and chemical properties of the emission-line nebulae associated with seven cluster cooling flows. We find that the gas is much more centrally concentrated than implied by the radial accretion profile inferred from the X-ray data. The kinematics show little evidence for ordered large-scale shears or rotation, but are consistent with infall and/or turbulence. Gas pressures on scales of 1-10 kpc are about 10 times larger than X-ray pressures on larger scales and the radial pressure profiles vary significantly among the different nebulae. We present several lines of evidence favoring shock-heating over photoionization. In particular, we can conclusively rule out photoionization by a dilute nuclear continuum source. Several models for the heating of the nebulae are briefly explored. Two classes of nebulae with different chemical abundances have been identified. Finally, we stress the physical relationship between the nebulae and the coterminous nonthermal radio plasma.

We report on the results of long-slit spectroscopy and interference filter imaging of powerful 3CR radio galaxies. Narrow-band [OII]A3727 imaging often reveals extensive regions of extranuclear emission associated with these objects. The extended [OII] emission is distributed on scales of several tens of kpc, it is often more luminous than the nuclear emission, and shows large velocity gradients. We discuss the physical conditions in these nebulae and their relation to the radio source structure. In particular, we examine the ionization mechanism for the gas, and find that photoionization models reproduce the observed emission line strengths reasonably well. The source of the ionizing photons, however, is not clear; the large luminosities of the extended gas suggesting that some form of in situ ionization may be occurring. Compared to the low-z cooling flow filaments, the 3CR emission regions are larger, more luminous, and generally show higher excitation. Futhermore, the distant radio galaxies show evidence for much stronger interactions with their radio sources than is seen in nearby cooling flow filaments.

The occurence of extended optical emission-line regions in many, relatively nearby radio galaxies is now well documented (Danziger, Fosbury, these Proc.; Heckman et al., these Proc.; Baum 1986; van Breugel 1986). In most cases the emission-line gas is found along the radio source axes and detailed studies of several sources have shown that many radio and optical properties are intimately related. Often emission-line regions are found adjacent to bright radio knots, and the radio morphologies appear distorted, indicating that jet/gas collisions occur. The low percentages polarization of the radio continuum, and large velocity gradients and line widths of the emission-line gas at these locations furthermore suggest that entrainment of surrounding gas occurs. Recent optical observations of more distant, very powerful (Cygnus A type) radio galaxies show that similar correlations may exist as in the nearby, lower power sources, but that the conditions appear much more extreme (McCarthy et al., these Proc).

A large fraction of sources in flux limited radio samples consists of compact steep spectrum (CSS) sources (Fanti et al. 1987). These objects have their dominant emission on kiloparsec scales and are found in a variety of active galaxies, including Seyfert II's, peculiar galaxies and quasars. Observations of very nearby CSS sources have shown good correlations between their complex radio structures and optical emission-line gas suggesting violent interactions between jets and dense gas in their ambient interstellar media (van Breugel et al. 1984). Similar jet/gas interactions may occur in more distant and more powerful CSS sources.

Optical identifications and redshifts are now available for nearly all 3CR radio galaxies (Spinrad et al. 1985; Djorgovski et al. 1988). Using new radio and optical observations, supplemented with data from the literature, we are conducting a systematic comparison of their radio and optical (emission-line and galaxy) properties, and their dependence on redshift. Here we present new results on the alignments of galaxies and their associated radio sources, and radio source asymmetries.

The radio source 3C293 has a bright, steep spectrum (α ≃ 0.7; Sν ∝ ν-α ) radio core with kiloparsec-sized structure (Bridle, Fomalont & Cornwell 1981, (BFC)). The core is misaligned by ~35° with respect to the extended radio lobes and both the core and lobes have a Z-shaped morphology. To explain this misalignment and morpholoqy. BFC propose a model in which beams ‘refract’ (buoyantly deflect) in a static hot gaseous halo. Alternatively, Wilson & Ulvestad (1982) have proposed that the source structure may be caused by ram pressure deflection of beams propagating through a rotating gaseous disk. Our optical imaging and spectroscopic observations reported here support the latter model.

The results of long-slit spectroscopy and narrow-band imaging of M82 and NGC 253, the two nearest examples of FIR luminous galaxies believed to be undergoing intense bursts of star formation, are presented. The profile of the gas pressure in the emission-line filaments in M82 is derived and found to be in good agreement with the model of Chevalier and Clegg (1985) of a supernovae-driven wind from a starburst nucleus. Lower quality data from NGC 253 support the same interpretation. Analysis of the emission-line ratios suggests that the line-emitting gas may be heated by low-velocity shocks, although photoionization from dilute UV radiation from unusually hot stars in the central starburst may also be important.

We report the discovery of a large cloud of ionized gas associated with the high-redshift radio source 3C 326.1 New radio-frequency images made at 4.9 GHz and 15 GHz with the Very Large Array show the radio source to be a small double (~ 7") without a detectable core at the level of ~ 0.5 mJy. Long-slit spectrograms and Lγa imaging reveal a ~ 100 kpc diameter cloud of ionized gas with a redshift of 1.825 encompassing the radio source. Deep broad-band images show two faint (V = 23.5-24.5) blue objects located on the periphery of the cloud, as well as some very faint (V = 25-26) extremely blue diffuse objects roughly coincident with the brightest regions of the cloud. Long-slit CCD spectra suggest that the Lγa emission from the cloud has a large intrinsic width (FWHM ≈ 1000 km s^(-1)). Spectra taken in the red show weak extended emission from C II] and C III], but C IV emission has not been detected. The large equivalent width of Lγa and the relative strengths of the carbon lines are consistent with H n region-type photoionization. We tentatively propose that 3C 326.1 is a young and/or forming galaxy.

The discovery of an unusual stellar object apparently associated with the powerful radio source 3C 435B is reported. Radiofrequency observations show that radio source to be composed of two extended sources with centroids separated by 10 arcsec and roughly equal flux densities. The smaller of the two sources is coincident with Smith and Spinrad's (1980) identification of an R = 19 galaxy at z = 0.461. The larger of the two sources consists of a strong core at 20 cm and two lobes. The core is coincident with a faint blue stellar object which has strong Balmer-series absorption lines of hydrogen at zero redshift. The spectrum also shows four strong, narrow emission lines identified as forbidden O II, forbidden Ne III, forbidden Ne IV, and forbidden Ne V at a redshift of 0.865. They have relative strengths typical of radio galaxies at z of about one. It is proposed that this is a rare case of an early-type high-latitude galactic star superposed along the line of sight to a distant radio galaxy. 26 references.

A search for extended optical-line-emitting gas in a representative sample of power radio galaxies has been conducted in order to determine the frequency with which such gas is found in these galaxies and to assess the relationship of the gas to the radio source structure and the structure of the host galaxy. Contour maps and detailed descriptions are given for each source of the broad-band optical, narrow-band optical, and radio images obtained. From the images presented here, it is clear that extended optical-line-emitting is common in powerful radio galaxies. In some cases, the emission-line filaments appear to connect the host radio galaxy to an apparent companion galaxy. S-shaped regions of line emission are observed in five of the sources. Morphological peculiarities in the distribution of the optical continuum light from the host radio galaxy are also apparent in many of these sources. 109 references.

We report the discovery of a strong correlation between the radio and optical morphologies of distant (z ≥ 0.6), powerful radio galaxies. The isophotal axes of highly elongated distant 3CR galaxies, measured both in the light of stellar continua and extranuclear emission lines, tend to align with the radio source axes. This correlation suggests that there is a profound relation between these extremely powerful radio sources and their host galaxies. We propose that the most natural explanation of the effect is that the radio jets and/or backflows from the radio lobes interact with the interstellar media of the gas-rich galaxies associated with 3CR sources and stimulate large-scale star formation. This proposed mechanism can provide a physical explanation for the high star formation and evolution rates of 3CR galaxies at large look-back times found in earlier photometric studies. Thus, the formation and evolution of powerful radio galaxies and radio-quiet giant ellipticals may differ substantially.