We have observed a group of optically selected quasars at a wavelength of 1.25mm with the Caltech Submillimeter Observatory in 1988 May. Except for Mrk 231, they were chosen from the PG sample of quasars (Schmidt and Green 1983) and are thus UV bright objects. All of them, except for PG 2209+184, were also detected at 60μm by IRAS.

Observations of NGC 4151 were made with the JCMT on UT 20 April 1988. The detector was the UKT14 system, a dual-beam, 3He cooled, composite doped Germanium bolometer. A bandpass filter was used to define a central wavelength of 438 μm (685 GHz) with a bandwidth of 84 GHz. The beam was approximately Gaussian, with a FWHM of 11′, and the pointing was good to A very significant 5σ upper limit of 200 mJy was obtained. The Figure shows the continuum energy distribution for NGC 4151, made without correcting for beam size. When combined with the measured 155 μm flux density of 4.8 Jy, a lower limit on the spectral index of α155–438μm ≥ +3.06 is derived. Since the steepest cut off allowed by synchrotron self-absorption is α = +2.5, these observations can place an upper limit on the flux at 155 μm arising from a synchrotron self-absorbed source, with the rest arising from a thermal dust source.

For the University of Michigan (UM) survey, the Curtis Schmidt telescope at CTIO is used with Kodak IIIa-J plates and the 1.°8 objective prism to detect emission-line galaxies (ELGs) and quasars. Line emission is the primary selection criterion. The quasar sample has been investigated by Lewis, MacAlpine, and Weedman (1979) and by MacAlpine and Feldman (1982) while a study of the ELGs was begun by Lewis (1983). Here, we report on a more extensive analysis of the 172 ELG candidates in the UM Lists IV (MacAlpine and Lewis 1978) and V (MacAlpine and Williams 1981) areas.

Megamaser emission provides new insights into the physics of active galactic nuclei. The megamaser phenomenon is consistent with a low-gain amplification model, where inverted foreground molecules amplify the radio continuum from the nucleus. The molecular gas seen in emission in the megamaser galaxies is located between 50 and 300 parsecs from the nucleus covering part of a possible NLR. Megamasers have been found for the molecules OH, H2CO and H2O. However, only OH megamasers form a clearly identifiable group of galaxies. They occur in prominent FIR galaxies and the FIR radiation field serves as a pumping agent for the OH molecules (Baan 1988). As a result only the ground state lines of OH are in emission, while the lines from excited states are in absorption (see Henkel, Güsten and Baan 1987).

Observations with the IRTF and IRAS indicate that there are at least two different mechanisms for the generation of infrared emission from radio galaxies.

The IRAS Point Source Catalog contains only 61 sources identified as galaxies whose energy distribution peaks at 60 mμ. The scarcity of such galaxies has prompted a search for possible common properties. This sample of ‘60 mμ peakers’, 21 of which are previously identified galaxies, partially overlaps with that of warm IRAS galaxies studied by de Grijp et al. (1987) and contains similar percentages of Seyfert (65%) and starburst galaxies on the one hand, and of strong and weak radio sources on the other hand. A remarkable characteristic is, however, that about half of the 60 mμ peakers seem to be early-type galaxies. The fact that such galaxies are rarely IRAS sources and, if so, have FIR energy distributions peaking at 100 mμ similar to those of spirals, implies that we are sampling active or nuclear starburst early-type galaxies with a very large success rate. The observational data accumulated so far further show that:

1. (i) objects with smaller FIR to near-IR flux ratios have redder J-K colors and warmer 60 to 25 mμ colors, i.e., an infared spectrum dominated by warmer dust and/or a nonthermal source (Figs. 1a,b);

2. (ii) out of 32 objects with radio data, the 5 compact radio sources with luminosities intermediate between those af radio-quiet and radio-loud AGN have among the warmest 60 to 25 mμ colors (Fig. 2). Such warm FIR colors are not a common characteristic of radio galaxies and quasars (Golombek et al. 1987, Neugebauer et al. 1986).

3. (iii) the 60 mμ luminosities range from 109 to 1012 L0, and are largest for Mkn 231, 2306+0505 (Hill et al. 1987) and 2046+1925 (Frogel et al. 1988). The latter 2 objects, along with 0052-7054 (Frogel and Elias 1987) which also belongs to our sample, are Seyfert 2 galaxies with evidence for the presence of a dust-obsured broad line region.

A sample of unusually warm IRAS galaxies with spectral energy distributions peaking at 60μm is studied. The complete sample consisting of 21 known galaxies and 40 previously unidentified galaxies is selected according to the following criteria: all galaxies in IRAS Point Source Catalogue with high quality detections at 25μm and 60μm, FIR fluxes such that 4>f60/f25>1 and f60/f100>1, and a galactic latitude of |b|>10°. The colour ctireria select against galaxies with a significant cool dust component and the hotter dust present is presumably circumnuclear (Vader et al., 1988). CCD imaging reveals a morphological dichotomy in our sample - the galaxies are either relaxed systems (E/S0) or interacting (double nuclei, tidal features etc.). The relatively fast process of merging may link these two types of systems.

It is well know that the determination of the local luminosity function of Seyfert nuclei meets several difficulties produced by: the determination of a suitable sample, the estimation of the nuclear magnitudes biased from the contribution from the host galaxies, which may be dominant if the nucleus is faints and the presumably large errors associated with the estimated magnitudes.

It has been known since the IRAS mission that there exist galaxies with far-infrared luminosities of 1011–1012Lo, and LFTR/LB = 10–100. Through extensive modelling and observations of HII-region/molecular cloud complexes in the Galaxy, this infrared radiation is believed to be thermal emission from heated dust grains (c.f. review by Stein and Soifer 1983). While starburst models are consistent with the data over a large range in wavelength, direct evidence for sizeable populations of young stars is scarce, and in many cases the presence of an active nucleus either cannot be ruled out, or is required on the basis of energy considerations. In order to better understand the energy source responsible for heating the dust, we have undertaken a spectroscopic survey of galaxies chosen to have far-infrared spectral energy distributions similar to the prototypical class members Arp 220, NGC 6240, NGC 3690, and Mrk 231. It was required that between 25μ and 60μ, α ≤ −1.5, and that between 60μ and 100μ, α ≥ −0.5, where Sv α vα.

We present results of number count studies of IRAS deep Pointed Observations and the new Faint Source Survey. Since number counts are dominated by the population near the knee of the luminosity function, the results refer to starburst and active galaxies with typical luminosities L60 ∼ 1010.5–11L⊙ and Lir/Lb, ∼ 3, and not to ‘normal’ spirals or the ‘ultraluminous’ IR galaxies.

IRAS made it possible for the first time to study infrared complete samples of galaxies. On the average these galaxies appear to emit most of their energy in the infrared in contrast to optical selected galaxies. The so-called minisurvey is the first infrared completem sample studied and additional observations in the optical, near-infrared and radio have already been done for these galaxies. The interpretation of these observations has not yet led to a clear and uniform picture of the astrophysical processes in these galaxies. The question whether these galaxies are highly obscured by dust or whether these galaxies experience starbursts is not yet satisfactory answered.

The Infrared Astronomical Satellite (IRAS) has detected many galaxies in the infrared (IR), most of which have fairly steep 25μ to 60μ spectra. Many quasars and active galaxies exhibit a significantly flatter spectrum in the infrared. Several studies, for example, DeGrijp et al. (1985) used this characteristic to select a subsample of “warm” objects from the IRAS PSC (1985).

We have made a statistical study of the optical and far-IR properties of all the Seyfert 2 galaxies in the catalog by Véron-Cetty and Véron (1987; hereafter VCV). Nuclear spectroscopic data were compiled from the literature and IR fluxes from the Catalogued Galaxies and Quasars Observed in the IRAS Survey (1985); we used only those IR fluxes not flagged as limits or uncertain values. We have used for comparison four more lists of objects with IRAS fluxes: one of Seyfert 1 galaxies given by Rodríguez Espinosa, Rudy and Jones (1987), a list of LINERs compiled from the literature, a sample of “normal” spirals (those labeled H in Keel, 1983), and finally the galaxies catalogued as Starburst nuclei galaxies in VCV.

35 years ago Baade and Minkowski (1954) suggested that a galaxy collision - diagnosed from the peculiar appearance of the parent object and its strong emission lines - is responsible for the strong radio-source CygA. This was the first time that gravitational interactions between galaxies were suggested to trigger nuclear activity. Over the following decades after the detection of the quasars and the gradual realization that quasars, comparable to the Seyfert phenomenon, are events at the nuclei of seemingly isolated galaxies, the collision hypothesis was abandoned. Efforts concentrated on the understanding of the activity as internal processes in the host galaxies, possibly aided by infall of gas from the intergalactic medium (cf. Rees, 1978; Gunn, 1979).

In the course of morphological survey of Markarian galaxies on 2.6 m telescope of the Byurakan Observatory four new double nuclei objects were discovered. The results of morphological investigation of these galaxies are given and some parameters of the objects and their nuclei are estimated.

The close-by double nucleus galaxy Mkn 673 shows spectra and colors which are typical for “E+A” cluster galaxies.

We present results of observations of the double-nucleus galaxy Markarian 266 (NGC 5256) from 3 principal sources. These are

1. 1: CCD imaging with the Canada-France-Hawaii telescope in broad and narrow bands. These indicate that the galaxy has extended, complex, faint outer plumes which indicate that a recent merger has occurred. The narrow-band images reveal remarkable knotty structure of the [O III] emitting gas, extending over the whole central part of the galaxy. This is not seen in Hα (see figure 1).

2. 2: 21cm imaging with the VLA, covering velocity space near that of the optical nuclei. The continuum image reveals resolved triple structure, with the two outer peaks coincident with the optical nuclei. The 21cm velocity profiles indicate the presence of considerable H I absorption near the optical emission line velocities.

3. 3: Spatially resolved optical spectroscopy with the DAO 1.8m telescope. These data reveal the details of the [O III] velocity field and some of the physical parameters of the gas. The complexity and extended nature of the gas explains some conflicting redshift measurements in the literature. Together with the imaging data, we derive estimates of nuclear reddening and luminosity.

An investigation of the physical conditions present in the circumnuclear regions of 20 nearby, non-interacting Seyfert galaxies is reported. Significant differences are observed between the circumnuclear properties of Seyfert 1s and Seyfert 2s with regards to extended ionized gas. The morphology and ionization of the circumnuclear gas suggests collimation of the nuclear ionizing radiation field; in 4 cases taking the form of distinct conical distributions of ionized gas emanating from the nucleus. Some of these properties are consistent with prevailing “unified” models for AGN. However, it is difficult to reconcile all of the observed differences between Seyfert 1s and 2s with this picture.

It has traditionally been accepted that quasars and strong emission-line radio galaxies, although situated in regions of enhanced galaxy density, are rarely found within rich clusters (Yee and Green 1984; Longair and Seldner 1978). The recent finding by Yee and Green (1987) that at z ≳0.5 a substantial fraction of optically bright radio-loud quasars are found in galaxy clusters as rich as Abell class 1, suggests that a substantial evolution of the environments of rich clusters has taken place over this short time period. Similar results for radio galaxies have also been obtained by Hill and Lilly (1988, private communication). If this is an evolutionary effect, then at least some first-rank elliptical galaxies in low-redshift rich clusters must contain remnants of active galactic nuclei (AGN). Motivated by this, we attempted to find traces of AGN-like activity in a sample of FR class I radio galaxies which are known to be “quiescent” absorption-line systems situated in low-redshift clusters.