Low flux radio sources are important for a variety of reasons. In principle, a 1 mJy survey that is over 1000 times fainter than the 3CR allows us to reach objects 20 times more distant, almost literally to the edge of the universe, or to detect much less luminous sources at the same distances. We can hope to detect primeval galaxies, to check the idea that objects with redshifts z greater than 3 or 4 are optically hidden by dust, to detect new populations of radio objects, to possess pointers to distant clusters and galaxies, as well as to understand better the AGN phenomenon.

This study of the activity in the nuclei of normal galaxies began as an investigation into the spread in the observed properties of normal galaxies used as standard candles in measurements of departures from the Hubble flow (Hart & Davies 1982). Extensive studies of the integrated properties of normal galaxies show the influence on these properties of quiescent star formation and embedded starburst-type activity (Staveley-Smith & Davies, 1987,1988). Normal galaxies have a significant level of nuclear activity, although it is not strongly correlated with their integrated properties. This investigation of nuclear activity is based on a sample of the 100 brightest nearby Sbc galaxies, a sample unbiassed in its selection of activity.

Galaxies were selected from the CfA redshift survey (Huchra et al. 1983, Ap.J.Suppl., 52, 189; Tonry 1984, private communication) according to: Decl.(1950) ≥ 0°; photographic or B(0) magnitude ≤ 14 mag; heliocentric velocity ≤ 3000 km s−1; and de Vaucouleurs morphological type T ≤ −1. The third criterion roughly corresponds to a distance limit of 40 Mpc for H0 = 75 km s−1 Mpc−1. The fourth criterion is equivalent to a Hubble morphological type of elliptical (E) or lenticular (S0), collectively referred to as E/S0 galaxies hereafter. 213 galaxies satisfy the above selection criteria, after 3 Local Group dwarf spheroidals are excluded. Various galaxy catalogs and the recent literature were consulted to check the CfA morphological classifications and to divide the galaxies into Es and S0s. These galaxies comprise a volume– and optical–magnitude–limited sample that is ideally suited to systematic searches in all spectral domains for low-power nuclear activity (Wrobel 1988, A.J., in press).

Very Long Baseline Interferometry at radio wavelengths is the only technique available for imaging the central few parsecs of powerful radio galaxies and quasars. VLBI observations have shown that in many nuclei radio-emitting material is collimated into a jet on a scale less than a parsec and ejected at relativistic velocities. The interpretation of the observations is complicated by the relativistic motion, however: the images are dominated by those parts of the source that are moving almost directly towards the observer, and thus amplified by relativistic aberration. Nonetheless, the VLBI images are vital for understanding the nature of the central engine, the cause of the collimation, and the physics of the jets.

Sholomitskii (1965) discovered that the flux density of the quasar CTA 102 varies at low frequencies on a timescale of a few months. Low-frequency variability can be explained by “superluminal flux variation” (Romney et al. 1984): If the intrinsic brightness of a component moving in a relativistically beamed source varies by only a few percent, the observer sees its flux density change by a much larger factor δ3-α when the optically thin blob moves almost directly toward the observer. Such a relativistically beamed source is likely to exhibit superluminal motion if studied with sufficient resolution and sensitivity. Superluminal motion in CTA 102 was discovered by Bååth (1987) who concluded on the basis of maps made at three epochs at a frequency of 932 MHz that two components were separating at a rate of 0.65 milliarcseconds (mas) per year. Using a redshift z = 1.037 and H0 = 100 km s−1 Mpc−1, q0 = 0.5, this expansion speed corresponds to (18 ± 4)h−1c. The extraordinarily high speed led us to make VLBI images of the source at a higher frequency in order to increase the resolution and make a more precise determination of the speed.

Quasars found in low frequency radio surveys are often assumed to have their jet axes randomly oriented in the sky because relativistically beamed radio cores rarely contribute significantly to the total flux density at metrewaves. But an orientation bias can still arise from the optical magnitude limit of the sample (Kapahi & Shastri 1987) if radio beaming is accompanied by an enhancement of the optical continuum as well (due to beaming or other effects). Such a bias can explain the finding (de Ruiter et al. 1986) that the typical value of R (ratio of core to extended flux density at 5 GHz) for the magnitude limited Bologna sample is about 5 times larger than for 3CR quasars, eventhough both samples are from low frequency surveys. It is thus consistent with the unified scheme for quasars (Orr & Browne 1982; Kapahi & Saikia 1982), which in fact requires an aspect dependence of the optical continuum (eg. Browne & Wright 1985; Browne & Murphy 1987).

Although initial, low resolution radio measurements by deBruyn and Wilson (1978), suggested that the radio emission in Seyfert nuclei was in approximate pressure equilibrium with thermal gas in the Narrow Line Region (NLR), higher resolution radio measurements using the VLA and MERLIN (eg Unger et al. 1985) showed that the radio components were at significantly higher pressures than the NLR thermal gas. This is even more apparent in the very long baseline interferometry (VLBI) observations using the European Network (EVN). Observations of NGC4151 (Harrison et al.1986) and NGC7674 (Unger et al. 1988) have already been described, together with a summary of work in progress by Pedlar et al. 1987. Several Seyfert nuclei have components in which relativistic particle/magnetic field pressures as high as 10−7 dynes/cm2 are infered. These observations are also consistent with the collimated ejection of either radio emitting ‘plasmons’ or beams from the optical nucleus.

Self-absorption of synchrotron radiation in compact radio sources gives rise to a low-frequency cutoff in their spectra. To study this effect it is necessary to observe the radio sources at meter wavelengths with angular resolution < 1″. Such observations of compact radio sources located in active galactic nuclei lead to estimates of magnetic field strengths and relativistic electron number densities in the AGNs.

It is now common practice for objects with a steep radio spectrum and compact radio structure to be lumped together and called compact steep spectrum (CSS) sources (Peacock and Wall, 1982; van Breugel, 1984 Fanti et al. 1985). This rather arbitrary categorisation results in the class containing sources with a wide range of structures, from core-jet or complex (e.g. 3C147,3C48), small classical doubles (e.g. 3C237, 3C241), to VLBI compact doubles (e.g. CTD93; Phillips and Mutel, 1982). Some of the questions we are asking include:

1. (a) Are compact sources intrinsically small, or do they appear small because they are seen in projection?

2. (b) Why are structures in compact radio galaxies and compact radio quasars different? Wilkinson et al. (1984) and Spencer et al (1988, in preparation)have shown that there appears to be a ‘clear-cut’ difference in morphology between quasar CSS and galaxy CSS, with quasars showing more distortions while galaxies tend to be doubles. But is this trend present even in their slightly more-extended counterparts?

A sample of more than 100 southern QSOs is being monitored for flux density variations by the Molonglo Observatory Synthesis Telescope (MOST). Provisional results for an interval of 4 years shows that the variability at 843 MHz is less than at 408 MHz. There seems to be a real ‘mid-frequency gap’ with little variability near 1 GHz.

In order to look at relationships among various optical and radio properties of powerful radio galaxies at high redshifts in a systematic way, we have observed a nearly complete subsample of the Laing et al. (1984; henceforth LRL) revision of the 3CR extragalactic source list. Our sample comprises the 14 radio galaxies in the LRL list with δ < 50° and 0.8 < z < 1.3. We have obtained images of 13 of the 14 galaxies (we are missing 3CR 175.1) in each of three bands. The filters used typically gave ∼ 200 Å (rest-frame) passbands shortward of 3700 Å and longward of 4000 Å (in order to give us a 4000 Å break index), as well as a 50 Å passband centered on the [O II] λ3727 line. The images were obtained with the Galileo/IfA TI 500 × 500 CCD system on the UH 2.2 m and CFHT 3.6 m telescopes on Mauna Kea. Absolute calibrations of the images were based on observations of Gunn-Oke spectrophotometric standard stars through the various filters. The photometry we discuss here used synthetic circular apertures closely matched for each object to those used by Lilly and Longair (1984), who give K magnitudes, at least, and sometimes J and H as well, for all objects in our sample.

The 3CR catalogue of extragalactic radio sources is now completely identified for b > 15° and redshifts have been determined for > 98% of them (see Djorgovski et al. 1988 for the latest update). The radio galaxies in this catalogue span the redshift range from 0 to 2.48. This sample provides us with a unique opportunity to examine the optical and radio properties of a complete sample over a look-back time comparable to the Hubble time.

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.

We have observed two high-redshift quasars with the echelle spectrograph and 2D-Frutti Photon Counter at Las Campanas, in order to investigate the statistical properties of the Lyman-α forest. The two-point correlation function for the Lyman-α forest lines at z ≈ 3 is consistent with zero, for all velocity splittings Δv > 50 km/sec. When Lyman-α lines and other metal lines from known metal-line systems are included, the correlation function shows a weak non-zero signal at small Δv. We suggest that the weak clustering of the Lyman-α forest detected by other workers may be the result of contamination by a small number of metal-line systems and their associated Lyman-α lines.

This is a study of the Lyman edge region in the spectra of eleven high redshift quasars. We present large aperture, low resolution data designed to detect broadened Lyman edge absorption predicted by thermal models of the Big Blue Bump continuum component. We also present high resolution data on the edge regions and the Lyman alpha emission line for nine of the objects. We show some partial absorption edges and discuss whether or not they can be interpreted as support for the accretion disk model.

The strong self-damped Lyman α absorption systems present in the spectra of high redshift QSOs represent a unique population of absorber which has recently been associated with the precursors of current disk galaxies. In a low resolution survey for what we have come to call “Lyman α disk systems” performed at Lick Observatory (Wolfe, et al. 1986, Ap. J. Suppl. 61, 249) approximately 18 systems with confirmed damped Lyman α profiles and rest frame equivalent widths greater than 5 Å were detected in a sample of 68 high redshift QSOs (Smith, Cohen and Bradley 1986, Ap. J. 310, 583). Subsequent higher resolution study has shown these systems to have the following properties (Turnshek, et al. 1988, Ap. J., in press):

1. 1. Neutral hydrogen column densities, 2 × 1020 ≤ NHI ≤ 8 × 1021 cm−2.

2. 2. Low-mixed ionization state. Typically the low ionization states dominate the high ionization states (e.g. CII ≫ CIV). Some enrichment has occurred, −2≲[X/H]⊙ ≲0.

3. 3. Gas density, n ≲ 1 cm−3.

4. 4. The gas shows two components, a quiescent (disk) component, σν ≲ 10 km s−1, and a turbulent (halo) component, σν ≲ 20 km s−1. Some systems show only the low velocity dispersion component.

5. 5. At least one system intervening toward a radio QSO (Pks 0458-020) shows 21-cm absorption. The system shows multiple cloud structure with σν ≈ 6 km s−1, Ts ≈ 100 K, and structure extended over several kpc on the sky.

6. 6. There is evidence that these systems may be self gravitating with scale height of the order of 300 pc.

7. 7. These systems represent a unique population of absorber (distinct from the ‘Lyman a forest’ and heavy element systems) covering approximately 20% of the sky to z ≈ 3 and accounting for all of the baryonic matter at that redshift.

We have obtained intermediate resolution spectra for about 30 galaxies, normal and active, in the near infrared region covering the CaII triplet (λλ 7800–9300 Å). The data were obtained with the INT at the Roque de los Muchachos Observatory in La Palma, Spain using the Intermediate Dispersion Spectrograph and a GEC CCD detector. Details of these observations are given elsewhere (Terlevich et al. 1988). Our data show that active (Seyfert galaxies and LINERS) and normal galaxies have comparable nuclear CaII strengths and line widths.

In the 1950s, V.A. Ambartsumian (1958) proposed that galaxies result from explosive processes in galactic centers. Soon after the discovery of powerful radio galaxies in this same period, it became clear that explosive ejection of gas and relativistic particles was a common feature of active galaxies (Burbidge, Burbidge and Sandage 1963).

The absolute spectrophotometry of 66 AGNs (de Bruyn and Sargent, 1978) is used to compute synthetic magnitudes and colors, and K-corrections in the UBV system. In our preliminary contribution (Kalinkov et al., 1988) only some results of (U-B)s and (B-V)s colors were given. Here we use the whole observational data given by de Bruyn and Sargent. Synthetic spectra for 41 Sy1, 7 Sy1.5 and 15 Sy2 galaxies are constructed in relative units, assuming f(λ5470) = 1000. Colors and K-corrections are obtained from the synthetic spectra. The variations with the redshift are presented in the polynomial approximation form X = aizi, i = 0,1,‥, where X = (U-B)ss, (B-V)ss, KB, KV (Table 1). The largest deviation in mag. from the computed curves is denoted by Q. The relations in Table 1 are very good approximations in the corresponding redshift ranges.