A comparison of the projected linear size evolution of extended quasars and radio galaxies are often used as a test of the radio galaxy - quasar unification schemes. If both the mentioned categories of radio sources differ to an observer only due to the various viewing directions, then their radio linear sizes are expected to evolve with redshift in the same way (Gopal-Krishna & Kulkarni, 1992). However, apart from the simplest linear size parameter L we can still determine two independent parameters assessing the asymmetry of the radio structure: Q - the arm lengths ratio; M - misalignment, which measures the apparent bending, and defined as the ratio of the displacement of the core from the source axis to the linear size. The asymmetry parameters Q and M can also be a powerful tool in the consistency test for the orientation based unification scheme as their evolutionary patterns should be the same for radio galaxies and quasars. Contrary to the linear size, they are not sensitive to the simple homological rescaling of the whole structure and hence to the age or expansion velocity of the structure.

A multidimensional statistical analysis of observed properties of Seyfert galaxies has been carried out using Principal Component Analysis (PCA) applied to X-ray, optical, near and far IR and radio data for all the Seyfert galaxies types 1 and 2 for the catalog by Lipovtsky et al. (1987).

We analyse the rest-frame UV spectra of a complete sample of optically selected radio-loud and radio-quiet QSOs. Our results are:

1. 1: Broad absorption-line QSOs (BALQSOs) are all radio quiet, but they are strongly clustered toward the top end of the radio-quiet population in radio power.

2. 2: Radio-loud QSOs have higher equivalent-width, narrower high ionisation emission-lines than radio-quiet QSOs.

3. 3: Further Reading

See Francis, Hooper & Impey, 1993, Astronomical Journal 106, 417 and references therein for more details and discussion.

Observations of nearby galaxies indicate non-negligible (dark) mass in their nuclei, interpreted either as very dense clusters or Massive Black Holes (MBH's). The latter hypothesis is supported by the widespread idea that MBH's can be the engine powering Active Galactic Nuclei (AGN's), and that interaction- or bar-induced central mass accretion can feed MBH's with large scale, plentiful fuel. However, there are fewer AGN's at the present time than at high redshifts, although many if not all bright galaxies must harbour relics of central active MBH's. How can we explain the fact that some AGN's are now turned off? Is it only due to the exhaustion or evaporation of the available fuel, and/or to the lower rate of interactions at the present epoch?

BL Lacs, Highly Polarized Quasars (HPQs) and Optically Violent Variables (OVVs) are classed as blazars. Based on the multifrequency spectral properties of these objects we have classified the blazars into two groups which are as follows:

• – Group I - BL Lacs

  BL Lac objects are soft X–ray sources (Hardness ratio is less than 5) with steep and flat spectral indices in the X–ray and ultraviolet bands, respectively. They are relatively less polarized (in the optical band) and low luminous objects (Mabs < −23). Radio to X–ray spectra of BL Lacs can be fitted with a single parabolic curve and these objects radiate most of their energies in the X–ray band (radio through X–ray frequencies).

• – Group II - HPQs/OVVs

  HPQs and OVVs are hard X–ray sources (Hardness ratio is greater than 5) with flat and steep spectral indices in the X–ray and ultraviolet bands, respectively. These are highly polarized and highly luminous (Mabs > −23) objects. Radio to X–ray continuum emission spectra of HPQs/OVVs can be fitted with two parabolic curves with the spectral break between UV and X–ray bands and these objects radiate most of their energies in the infrared band.

We have constructed radio to X-ray energy distributions for a large number of BL Lacertae objects using archival data. We find that Radio to optical spectra of RBLs and XBLs are very similar. Large differences are seen at higher frequencies where RBLs very frequently show a cutoff near the optical band while XBLs usually do not show any turnover before UV/X-ray energies. Our data is consistent with a picture where RBL and XBL are from the same parent population, the XBL simply being those (rare) objects where the break in the energy distribution is located at high energy.

Optical identification of bright sources from the ROSAT All-Sky Survey has led to the discovery of 40 new Seyfert galaxies with very soft X-ray spectra. Nearly half of these are narrow-line Seyfert 1 (Hβ-FWHM < 2000 km/s) with strong optical FeII emission, suggesting the presence of an unseen hard X-ray component. The remainder are Sy1.5 and a few broad-line Sy1.

Numerous narrow absorption lines in the region of wavelength shorter than 1216(1+zem ) (zem is the emission redshift), i.e. so-called Ly α forest lines, detected in QSO spectra are usually thought to be produced in intervening primeval clouds. The study of Ly α clouds may reveal how matter distributes in space and how it evolves with time at the early universe and provide valuable information about the large scale structure of the universe and its evolution. Based on intermediate resolution (1 ∼ 2 A) spectra, many authors (e.g. Lu et al. 1991) deduced that the evolutionary index γ ∼ 2, (dN/dz ∼ (1 + z)γ, dN/dz is the number of clouds per unit redshift interval at redshift z). It means that Ly α clouds have strong cosmological evolution. In recent years, there appear high-resolution (< 30km/sec) spectra of QSOs. High resolution spectra may provide more information than medium resolution spectra. Hence, it is necessary to study the evolution of Ly α clouds, using the spectra with higher resolution. Carswell et al. (1987) found γ=1 in the redshift interval 1.9–3.8. But Rauch et al. (1992) found γ=2.1 for the line sample with logN(HI) ≥ 13.75. It is more interesting that Giallongo (1991) found a differential evolution: γ is depended on the equivalent width W of line and no evolution for the strong line sample with 0.5 > W > 0.3. However, these studies involved very few QSOs (three or four). In this paper, we use a larger sample of QSOs to study the evolution of Ly α clouds.

We present a comparison of well defined continuum slope distributions for QSOs found in the LBQS (Chaffee, F.H. et al. 1991, Astron. J., 102, 461 and references therein) and in the Hamburg–ESO–survey (hereafter HES) (Reimers, D. 1990, The messenger 60, 13).

For a model of the World with q 0 = 0.5 and H 0 = 100h −1 there was received a 2-point spatial correlation function (CF) (The sample of 300 objects with z < 0.045 and δ > 0 was used) for Seyfert Galaxies with the following parameters: r 0 = (9 ± 2)h −1 Mpc, γ = –(1.7 ± 0.2).

The observed correlation between activity and mergers of galaxies may be explained by the compensation of the angular momentum by merging. This leads to accretion on the galaxy centre.

Increasingly, the evidence from optical and infra–red wavebands suggests that the difference between Seyfert 1 and Seyfert 2 nuclei is due largely to orientation effects rather than intrinsic differences between the two classes, but the evidence from radio observations has been less clear–cut. We have observed the CfA Seyfert Sample at 8.4 GHz using the VLA in A– and C–configurations. At this frequency our A–array maps have a resolution of 0.25″ – much higher than those achieved in previous surveys – whilst the 3″ C–array beam is ideal for measuring the total radio flux of the active nucleus. The 1–sigma noise in both sets of observations was 70 μJy.

The fact that the recognition of BL Lacs always requires optical confirmation, regardless of whether the objects were first selected in the radio, or X-ray frequencies means that deep surveys will miss some objects simply because the optical emission from the host galaxy outshines that of the BL Lac. In particular, the deeper the survey, the more difficult it will become to recognize low luminosity BL Lacs in the nuclei of luminous galaxies. This recognition effect will modify the intrinsic distribution of objects, and influence their statistical properties in general.

While the energy distributions of optically and radio selected quasars have the same, reproducible, mean shape in the infrared to ultraviolet region, the strength of the infrared and ultraviolet components can vary by over a decade from object to object.

The field studied is part of the Hamburg Quasar Survey (Engels et al. 1988, PASPC 2, 143). It contains a spatially and magnitude (down to ∼ 18.m 5) complete AGN sample. Several follow-up observations were made: a deep radio continuum survey at 21 cm and 74 cm, a HI survey and a ROSAT survey consisting of 48 overlapping PSPC pointings with .

The flux of narrow 5007 Å [OIII] forbidden line during last 20 years is accepted as a bench-mark for calibration of the continuum and broad-lines fluxes in AGN. But one can not get away from the problem of the forbidden lines variability in these objects. The first report were published by Bardin et al. (1967). Some of the results are revieved by V. Pronik, I. Pronik (1988, 1992). There were 4 years monitoring of [OIII] fluxes variability in the Seyfert galaxy NGC 1275 nucleus (Pronik et al., 1990). Now we reexamine the published data of W. Zheng et al. (1986, 1987, 1988), discussed earlier in supposition of forbidden lines constant in spectra of 11 low-redshifted QSOs. Maximal calibration coefficients adopted by W. Zheng et al. in supposition of [OIII] lines constant were in the interval 2.0–3.6. On the other hand the fluxes errors are about 15%. Disagreement is very high. This is one of the arguments in the forbidden lines variability Tightness.

It is not yet clear which is the role played by interaction on Seyfert activity. Presently there are on this topic contradictory statistical results, based on the study of more or less rich samples of Seyfert galaxies. Petrosian (1982), Dahari (1985) and Mac Kenty (1989, 1990) found an excess of Seyferts among galaxies which have nearby companions and an excess of galaxies with nearby neighbors among Seyfert galaxies. The contrary result was found by Bushouse (1987) and by Fuentes Williams & Stocke (1988). In order to find more reliable conclusions, taking advantage of the increased number of Seyfert galaxies identified in the last years, we have applied the statistical procedures used by Dahari (1985) to a sample of 287 Seyfert-1 (S1) and 195 Seyfert-2 (S2) (namely to all known S1 and S2 galaxies with z ≤ 0.11 and δ ≥ −23°). A subsample has been extracted carefully excluding objects, identified as Seyfert on the basis of their morphology (e.g. on the basis of the presence of a companion) and brighter than mB = 15.5, the magnitude at which the cumulative number of S1 and S2 galaxies becomes flat. The possible companions of our Seyfert galaxies have been identified on the blue POSS prints by visual inspection looking for objects not more distant than 3 diameters from the Seyfert galaxy and not more than 3 magnitudes fainter. It results that ∼35% of both the S1 and S2 galaxies have a neighbor. This percentage is reduced to ∼14% for both classes of galaxies excluding the possible optical companions, the upper limit to the number of which has been derived starting from the counts of galaxies published by Shane and Wirtanen (1967), assuming that the probability of finding an optical companion is a Poisson probability. The same procedure applied to a control sample of 281 normal galaxies indicates that only ∼3% of the galaxies have a close companion. In conclusion Seyfert galaxies show a larger percentage (14%) of objects with companion than normal galaxies do (3%). This excess, which is the same for S1 and S2 galaxies, has been derived overestimating the number of optical companions and its value is then a lower limit.

We have studied the Hubble diagram for an almost complete sample of 48 Seyfert galaxies. We find that if Malmquist bias is taken into account, the correlation of [log(cz), V] pairs for Seyfert galaxies is statistically significant and that the slopes of the two regression lines are consistent with those expected if the redshifts of Seyfert galaxies are cosmological.

Supermassive black holes in AGN can form directly as the results of collapse of supermassive magnetic and rotating stars (gravimagnetic rotators). In this case naturally we can consider the binary magnetic rotator systems as progenitors of active galactic nuclei. One of the most important consequence of this scenario is an existence of moving galactic nuclei, so called “nomadic” nuclei.

We report on the results of a near-infrared imaging survey of low-redshift radiogalaxies. We find that one of our 13 objects harbours an unresolved source at K, which we interpret as a quasar-like central engine seen through ∼ 40 magnitudes of visual extinction.