We present CCD imaging results of our sample of IRAS galaxies with spectral energy distributions peaking at 60μm (Vader et al 1988). The results support our suggestion that the activity in 60μm peaking galaxies is centrally concentrated, and represents an early stage of dust-embedded nuclear activity. This activity is probably triggered by a recent interaction/merger event as indicated by their peculiar optical morphologies. We propose that 60μm peakers are the precursors of S0’s in the case of amorphous systems, and ellipticals in the case of interacting galaxies.

Almost a decade ago, the morphological similarities between patterns seen in Seyfert galaxies and those produced by gravitational forcing led to the suggestion that Seyfert activity might be fueled by material inflow induced by either a central bar or a perturbing companion (Simkin, Su, and Schwarz, 1980). More recent theoretical calculations suggest that such a feeding mechanism may involve a central bar-like, structure even if initially induced by the tidal effects of a companion galaxy (Noguchi, 1988a,b).

We describe work leading to the suggestion that interaction between infalling cool gas and ambient hot, coronal plasma in elliptical galaxies is responsible for emission filaments, and might remove the need for large mass depositions in cooling flows. A test of the hypothesis is undertaken — the run of surface brightness with radius for the emission lines — and the prediction agrees well with the data.

We discuss our program of narrow-band (Hα + [Nil]) imaging of a sample of 30 powerful far-infrared galaxies (FIRG’s) chosen to have far-infrared spectral energy distributions similar to the prototype FIRG’s Arp 220, NGC 3690, NGC 6240, and M82. The emission-line nebulae of these IR color-selected sample (ICSS) galaxies as a class are both impressively large (mean half light radius, r ~1.3 Kpc, and mean diameter, D ~16 Kpc) and luminous (LTOT ~108 Lo; uncorrected for internal extinction). The mean total Hα + [Nil] luminosity of the FIRG’s is comparable to that found for pairs of optically selected interacting galaxies (Bushouse, Lamb, and Werner 1988), but is a factor of ~5 greater than that of isolated spirals (Kennicutt and Kent 1983). Only ~25% of the nearby (z ≤ 0.10) FIRG’s have morphologies suggesting that large HII~regions contribuí significantly to their emission-line appearance. The broad-band morphologies of our IR color-selected galaxies fall into three major categories. Nearly 75% are single galaxy systems, with the remaining FIRG’s being either multiple nuclei systems, or members of interacting pairs. Since we see few (10%) currently interacting FIRG’s, yet many (80%) with highly distorted continuum morphologies, our IR color criteria may be preferentially selecting galaxies that have undergone highly inelastic, rapidly merging interactions.

The empirical connection between gravitational and collisional interactions among galaxies and enhanced activity has been well-documented. However, the physical mechanisms which are responsible for triggering the various forms of activity have not been determined. We present the preliminary results of a study of the nuclear and integrated infrared properties of galaxies chosen from the Catalog of Isolated Pairs of Galaxies in the Northern Hemisphere (Karachentsev 1972; hereafter CPG) and the Catalog of Isolated Galaxies (Karachentseva 1973; hereafter KI). Observations of these large, unbiased samples of paired and isolated galaxies are analyzed with the hope of identifying which aspects of galaxy encounters are most closely coupled to the presence of activity.

The nucleus of the Seyfert galaxy NGC 1275 was observed in the B system on 12-1-1989 with seeing 07 using the Zeiss-1000 telescope on Mount Majdanak in Central Asia. Special methods of processing reveal low-contrast details. The nucleus and circumnucleus are stretched in NW-SE direction. There are two narrow filaments near the nucleus in position angles roughly 340° and 320°. The first is directed near the radio jet of the nucleus, the second has broken details curved to the NW or toward the high-velocity system of NGC 1275.

We present broad and narrow bandwidth imaging of three southern elliptical galaxies which have flat-spectrum active radio cores (NGC 1052, IC 1459 and NGC 6958). All three contain dust and extended low excitation optical line emission, particularly extensive in the case of NGC 1052 which has a large Hα + [Nil] luminosity. Both NGC 1052 and IC 1459 have a spiral morphology in emission-line images. All three display independent strong evidence that a merger or infall event has recently occurred, i.e., extensive and infalling HI gas in NGC 1052, a counter-rotating core in IC 1459 and Malin-Carter shells in NGC 6958. This infall event is the most likely origin for the emission-line gas and dust, and we a currently investigating possible excitation mechanisms (Sparks et al. 1990).

The occurrence and quantitative properties of Seyfert 1 and Seyfert 2 galaxies as a function of the galaxy environment have been studied in a systematic way. For this investigation we have selected from the Catalogue of Quasars and Active Nuclei (Veron & Veron, 1989) all Seyfert galaxies with the following properties:

This results in a sample size of 242 Seyfert galaxies. For all these objects their galaxy environment has been inspected on POSS and ESO/SRC plates.

The vicinity of each sample Seyfert galaxy was searched for companion galaxies out to at least 0.5 Mpc. Lacking redshift information we adopted as a companion galaxy any galaxy in this area having a size between 20 and 200 percent of the Seyfert galaxy size.

One of the most notable results of the IRAS mission was the recognition of a class of galaxies with large bolometric luminosities, most of whose radiation emerges in the far-infrared (typically 50-100μ). The space density of these “IRAS galaxies” approaches that of QSOs for comparable luminosities, so that these are a significant component of the population of galaxies. The frequent occurrence of interacting and merging galaxies among these infrared-bright systems has underscored the importance of understanding how various energetic processes (active nuclei, starbursts) are related to the disturbances produced during galaxy encounters. The same material directly responsible for the signature infrared excess of these systems degrades many of the diagnostics normally useful for probing the nature of he observed activity, so that in many systems it remains unclear just what kinds of phenomena are being observed.

We have observed the superluminous, infrared galaxy NGC 6240 (z = 0.025) at Ha with the Hawaii Imaging Fabry-Perot Interferometer (HIFI – Bland and Tully 1989). During the past decade, observational evidence from all wavebands indicates that the unusual appearance of NGC 6240 has resulted from a collision between two gas-rich systems, a view which is supported by our spectrophotometnc data. However, the origin of the enormous infrared luminosity (4 × 1011 L0) detected by IRAS remains highly controversial, where opinions differ on the relative roles of large-scale shocks, massive star formation or a buried “active” nucleus. These mechanisms are discussed in the light of our Fabry-Perot observations.

Despite intense theoretical and observational effort during the past few years, two important questions in the field of active galaxies remain open and are the subject of vigorous debate.

The first concerns the connection between the interaction/merger of galaxies and the generation of starburst and/or active nuclei. A large fraction of high luminosity radio galaxies (Baum et al. 1988), quasars (Hutchinga, 1987) and IRAS galaxies (Sanders et al. 1988), show the presence of a large companion or have a peculiar optical morphology which is offen interpreted as evidence of a recent merger or interaction. In Seyferts, there are also several examples of individual galaxies with clear evidence of interaction/merger (Colina et al. 1987; Fricke and Kollatschny, 1989; Macchetto et al. 1990). Also a significant fraction of low luminosity radio galaxies are associated with a system of two elliptical galaxies in interaction (Colina and Pérez-Fournon, 1990a,b).

The “redshift controversy” can be said to have originated from studies of pairs and compact groups. There are two potential problems involving the measured redshifts of galaxies in interacting systems: 1) the question of the physical association of galaxies in pairs and groups with discordant (ΔV0 ≥103 kms-1 redshift and 2) the possible quantization of redshifts in samples of pairs regarded (on the basis of redshift difference) as physical. The emphasis in the panel discussion was on the latter problem.

It is now generally agreed that if quasars and nearby low redshift galaxies are associated, then there should be luminous connections between them. However, most of the observational evidence being presented is in the optical domain, whereas such evidence should also exist at radio frequencies. We are, therefore, investigating some QSO—Galaxy pairs at radio frequencies to search for luminous connections and other structural peculiarities. Radio maps of some of these sources are presented.

There are a number of known quasars for which our line of sight to the high redshift quasar passes within a few Holmberg radii of a low redshift galaxy. In a few of these cases, spectra of the quasar reveal absorption by gas associated with the low redshift galaxy. A number of these pairs imply absorption by gas which lies well outside the optical disk of the associated galaxy, leading to models of galaxies with ‘halos’ or ‘disks’ of gas extending to large radii. We present observations of 4 such pairs. In three of the four cases, we find that the associated galaxy is highly disturbed, typically due to a gravitational interaction with a companion galaxy, while in the fourth case the absorption can be explained by clouds in the optical disk of the associated galaxy. We are led to an alternative hypothesis concerning the origin of the low redshift absorption line systems: the absorption is by gas clouds which have been gravitationally stripped from the associated galaxy. These galaxies are rapidly evolving, and should not be used as examples of absorption by clouds in halos of field spirals. We conclude by considering the role extended gas in interacting systems plays in the origin of higher redshift quasar absorption line systems.

Central to any analysis of dynamical systems, or large scale motion, is the interpretation of redshifts of galaxies as classical Doppler velocity shifts. This is a testable assumption and for many years evidence has accumulated that is inconsistent with the assumption. Here we review recent evidence suggesting systematic radial dependence and temporal variation of redshifts.

Measurements of the velocity differences (Δυ’s) in pairs of galaxies from large statistical samples have often been used to estimate the average masses of binary galaxies. A basic prediction of these models is that the Δυ distribution ought to decline monotonically. However, some peculiar aspects of the kinematics have been uncovered, with an anomalous preference for Δυ ≈ 72 km s-1 appearing to be present in the data.

In this paper we suggest a possible alternative explanation of cosmological red shift. We consider that there exists a background field in the universe, and that light (the photon) has an extremely weak interaction with this background, and as result, experiences an energy loss. By analogy with damped oscillations, we introduce a dumping term with the first derivative with respect to time in the wave equation. The solution yields a linearly reduced freguency of the light with travel distance. The purpose of this exercise is to demonstrate how a simple alternative interpretation of the Hubble relation can be generated.

In mergers of galaxies their central black holes are accumulated together. We show that few-black hole systems arise which decay through black hole collisions and black hole ejections. The ejection statistics are calculated and compared with two observed systems where ejections have been previously suggested: double radio sources and high redshift quasars near low redshift galaxies. In both cases certain aspects of the associations are explained by the merger hypothesis.