We study the characteristics of global oscillation modes of masing disks in megamasers and the effect of the modes on the disk kinematics. We find that the eccentric mode is responsible for the observed sub-Keplerian velocity distribution of the maser source of NGC 1068, whereas in the masing disk of NGC 4258 the warping mode is dominant so that the angular rotation velocity remains near Keplerian.

I review recent results for quasars and discuss how they are related to activity in galaxies. Topics included are studies of quasar host galaxies with HST; searches for quasars in the Hubble Deep Field; evolution of the quasar luminosity function; news highlights from astro-ph; and current observational research problems and their relation to theoretical work.

I report results from analysis of data from several quasar samples (Durham/AAT, LBQS, HBQS and EQS) on the density and the luminosity evolution of quasars. We have used new statistical methods whereby we combine these different samples with varying selection criteria and multiple truncations. With these methods the luminosity evolution can be found through an investigation of the correlation of the bivariate distribution of luminosities and redshifts. Of the two most commonly used models for luminosity evolution, L = ekt(z) and L = (1 + z)k', we find that the second form, with k' = 2.58 (one σ range [2.14,2.91]), gives a better description of the data at all luminosities. Using this form of luminosity evolution we determine a global luminosity function and the evolution of the co-moving density for the two classes of cosmological models. We find a gradual increase of the co-moving density up to z ˜ 2, at which point the density peaks and begins to decrease rapidly. This is in agreement with results from high redshift surveys and in disagreement with the pure luminosity evolution (i.e. constant co-moving density) model. We find that the local luminosity function exhibits the usual double power law behavior. The luminosity density is found to increase rapidly at low redshift and to reach a peak at around z ≍ 2. This result is compared with those from high redshift surveys and with the evolution of the star formation rate.

Being dominated by non-thermal emission from aligned relativistic jets, blazars allow us to elucidate the physics of extragalactic jets, and, ultimately, how energy is extracted from the central black hole. Crucial information about jet structure is provided by the spectral energy distributions from radio to γ-rays, their trends with luminosity, and correlated multifrequency variability. Since blazar jets have broad implications for all radio-loud (and possibly radio-quiet) AGNs, we also need to understand their circumnuclear structure, especially the details of the physical and dynamical conditions of the highly ionized gas on sub-pc scales, which could be directly related to jet formation and radiative power. Eventually, the bulk of information provided by blazars will help us clarify the origin of the radio-loud/radio-quiet AGN dichotomy, one of the most outstanding open issues of extragalactic astrophysics.

Since this symposium is devoted to the 90th anniversary of Prof. Ambartsumian's birthday I would like to touch briefly upon some historical aspects of V. Ambartsumian's ideas on activity of nuclei of galaxies.

Giant radio galaxies are thought to be massive ellipticals powered by accretion of interstellar matter onto a supermassive black hole. Interactions with gas rich galaxies may provide the interstellar matter to feed the active galactic nucleus (AGN). To power radio lobes that extend up to distances of hundreds of kiloparsecs, gas has to be funneled from kiloparsec size scales down to the AGN at rates of ˜1 M⊙ yr−1 during ≥108 years. Therefore, large and massive quasi-stable structures of gas and dust should exist in the deep interior of the giant elliptical hosts of double lobe radio galaxies. Recent mid-infrared observations with ISO revealed for the first time a bisymmetric spiral structure with the dimensions of a small galaxy at the centre of Centaurus A (Mirabel et al. 1999). The spiral was formed out of the tidal debris of accreted gas-rich object(s) and has a dust morphology that is remarkably similar to that found in barred spiral galaxies. The observations of the closest AGN to Earth suggest that the dusty hosts of giant radio galaxies like CenA, are “symbiotic” galaxies composed of a barred spiral inside an elliptical, where the bar serves to funnel gas toward the AGN.

The second part of the First Byurakan Survey is aimed at detecting all bright (B < 16.5) UV-excess starlike objects in a large area of the sky. By comparison with major X-ray and radio surveys we tentatively identified as QSOs 11 FBS objects. We made spectroscopic observations of nine of them. We found six new QSOs bringing the total number of known QSOs in this survey to 42.

By comparison with the Palomar Green (PG) QSO survey, we found that the completeness of this last survey is of the order of 70% rather than 30–50% as suggested by several authors.

We present low resolution spectrophotometric and imaging ISO observations of a sample of 58 AGN's over the 2.5–11.6 μ range. The data strongly support unification schemes and set new constraints on models of the molecular torus.

On the basis of the Second Byurakan Survey (SBS) we have produced the largest and most homogeneous new complete samples of faint Markarian Galaxies and bright QSOs. The volume of reliable investigation of UVX galaxies reaches to ˜ 200 – 250Mpc,– ten times deeper than the FBS.

New reliable data for the surface density of bright QSOs in mag. range 16.05 < B < 17.45 and redshift 0.3 < z < 2.2 are presented. The complete sample of bright(B < 17m5) SBS QSOs contains 93 QSOs in these ranges. The new data allow us to assume that bright QSOs fast evolution might be perhaps the result of a selection effect.

A new sample of some 900 faint IRAS galaxies will be constructed after optical identifications of all IRAS point sources from PSC and FSC in an area with 1500 deg2 at high galactic latitudes. The identifications are being made on the basis of FBS low-dispersion spectra, DSS images and infrared colours. Some 320 IRAS sources have been identified and 180 galaxies have been found. Spectral observations of these objects revealed new AGN and luminous infrared galaxies.

The current state of investigation of galaxies in seven fields of the Second Byurakan Sky Survey (SBS) is presented. These fields have been selected by the results of completeness estimation of the samples of galaxies in 65 fields.

Observations of the SBS faint candidate galaxies are carried out to complete spectroscopy of galaxies in the selected fields. Currently in one SBS field, with coordinates of center α=15h30m and δ=+59°, the spectra of all galaxies have been obtained and reduced. Besides the redshift and spectral classification, these data allow estimates of the quality of object selection in the Second Byurakan Survey at faint magnitudes.

Identifications of IRAS sources with faint Markarian galaxies on the base of the Second Byurakan Survey were made. It is shown that about 30% of SBS galaxies are also IRAS sources. The list of newly identified objects is presented.

The jets of radio galaxies have an essential role in the formation of their extended components. However, in general, the physical characteristics of the jets differ from the characteristics of the extended components (the spectra, polarisation, density and so on).

Variability may be a common property of AGNs. It provides a powerful tool to study the physics of AGNs. For QSOs, variability is a suitable criterion for selecting candidates. Many variability studies on quasar samples have been made (e.g. Netzer and Sheffer 1983, User et al. 1983, Pica and Smith 1983, Wampler and Ponz 1985, Neugebauer et al. 1989, Huang et al 1990, Cristiani et al. 1990, Giallongo et al. 1991, Cimatti et al. 1994, Treverse et al. 1994, Hook et al. 1994, Cristiani et al. 1996, Axetxage et al. 1997). In some studies, a large percentage of quasars is found to have detectable variation. However, other studies find no variability evidence. Many studies also discuss the correlations of variability with luminosity or redshift. Some interesting results have been made. However, up to now, there are no positive conclusions. Further study on variability of quasar samples is obviously needed. In this paper, we report on a variability study of 32 members at the Medium Bright Quasar Sample (Mitchell et al. 1984). The study is actually a continuation of the previous study (Huang et al. 1990).

We present and discuss Johnson – Cousins V and R photometry of the highly luminous quasar HS 1946+7658 (z = 3.051). We found no evidence for strong variability during one year of monitoring.

First results of six frequency observations at five epochs in March, 1997, –- April, 1998, and a statistical analysis are presented.

Submillimetre imaging (350 μm to 850 μm) and millimetre photometry (1.35 mm and 2 mm) observations, obtained with SCUBA (Holland et al. 1998), are used: (1) to investigate electron aging for synchrotron emission and (2) to determine the dust content in Cygnus-A.

Many ultraluminous infrared galaxies (ULIRGs) are powered by quasars hidden in the center, but many are also powered by starbursts. A simply diagnostic diagram is proposed that can identify obscured quasars in ULIRGs by their high-ionization emission lines ([O III]λ5007/Hβ ≳ 5), and “warm” IR color (f25/f60 ≳ 0.25).

Constraints on the emission mechanism of AGNs can be provided by the variability of their spectral energy distribution (SED). Recently Di Clemente et al. (1996) have shown that the positive correlation of QSO variability with redshift can be due to a hardening of the spectrum in bright phases, coupled with the increase of the rest-frame frequency of the (fixed) observing band, for increasing redshift. Direct evidences of slope changes in the SEDs of a limited number of individual AGNs have been provided by Cutri et al. (1985), Edelson et al. (1990), and Kinney et al. (1991). In the following we present some preliminary results of a direct measure of variations of the SED slope in the complete, magnitude limited, sample of QSOs of the Selected Area 57 (Koo, Kron & Cudworth 1986; Trèvese et al. 1989 (T89)). The data are derived from two sets of prime focus plates of the SA 57, in the U, BJ, F and N bands, obtained with the 4-m telescope at the Kitt Peak National Observatory at two epochs separated by one year. Photometric methods and signal-to-noise optimization are described in T89 and Trèvese et al. (1994). The quasar sample, of < z > ⋍ 1.4, consists of 33 objects from T89, plus the brightest 3 members of the the Bershady, Trèvese and Kron (1998) sample of extended objects selected on the basis of variability. In Figure 1a Δα is reported versus the changes Δlog fv in the BJ band and shows positive correlation, indicating a hardening of the spectrum in the bright phase. A special care is needed to avoid spurious Δα – Δlog fv correlations (see Massaro & Trèvese 1996). The correlation coefficient is r=0.46 with a probability P(>r)=0.995, after the exclusion of one deviant point, whose inclusion would produce a higher correlation. The slope of the linear regression of ΔαΔlogv is b=1.9. Assuming that the spectra are, dominated by the big blue bump (BBB) in the sampled spectral region, around λ ≍ 2000 Å, we can use the simple approximation of a single black-body spectrum. To check the hypothesis that both the slope and brightness changes are caused by a temperature variations only, we derive the black-body temperatures from the SED slope as deduced from a linear fit of the log fv v.s. logv relation, based on the U, BJ and F data. The average slope (excluding the two highest and lowest z objects) is 〈α〉=-0.4±0.6 and the average temperature is T ≍ 25000 K. For a black-body of fixed emitting surface and varying temperature T, the changes of the local SED slope and the relevant luminosity variations are related by (dα/dT)/(dlogBv/dT) ≡ f(x), where x ≡ hv/kT. The slope b of the linear regression of Δα v.s. log fv of Figure la is compared with the function f(x) values of the sample determined by the dispersion of α. We can conclude that dα/dlogBv and α are consistent for x ≍ 3. For an average sampling wavelength < λ > ≍ 2000 Å of the sample, this corresponds to an average temperature T ≍ 2.5 × 104 of a black-body of fluctuating temperature.

The galaxy Markarian 231 is reviewed as a prototype that includes all physical processes associated with active galaxies. It contains both a starburst and an AGN which are highly obscured by dust. Its luminosity at various wavelengths is used to summarize how such a galaxy would appear at high redshift, as observed with missions such as HST, AXAF, and SIRTF. The conclusion is that Markarian 231 provides an excellent example for comparing low redshift and high redshift phenomena.