NGC 891 is a spiral galaxy very similar to our Galaxy, almost perfectly edge-on (i ≃ 89°) and nearby (D = 9.5 Mpc). For these reasons it has become a key system for the study of the vertical distribution of the interstellar medium in a spiral disk.

Since observations of elliptical galaxies show only a small fraction of gaseous matter, dissipationless N-body models are mainly used to follow the dynamical evolution of these systems. In order to end up with the observed de Vaucouleurs profile these models must be initially very cold which leads finally to a velocity distribution that is isotropic in the core and has a positive anisotropy A ≡ 1 − (σθ/σr)2 in the outer region (σθ, σr are the velocity dispersions in meridional and radial direction.). Contrary to these models, dissipative N-body simulations based on the idea of protogalaxies consisting of inelastically colliding clouds give negative anisotropics outside the core (see Figure). This dominance of circular orbits is caused by a combination of an orbit-dependent collision rate and a conservation of a negative anisotropy formed during the early collapse phase. Therefore, measurements of the anisotropy in galaxies can provide a tool for the study of the dissipative processes in the early galactic evolution.

We report on the detection and analysis of hot ionized gas in three groups of galaxies (MKW 4s, AWM5, NGC 6329 group) at distances above 100 Mpc (recession velocities above 8000 km s−1). In all three cases their emission is centered on the dominant member of the group (NGC 4104, NGC 6269, NGC 6329, respectively). The central electron densities of the gas ne,0 are about 0.02 cm−3, decreasing to the outside as: ne = ne,0 [1 + (r/rc)2]-3β/2, with an exponent β=0.40 ‥ 0.77, (see Tab. 1). In each case, the spectra are well-represented by thermal Raymond-Smith spectra with kT ≃ 1.0 to 1.3 keV in the center and a weak increase by ca. 0.5 keV to the outside, indicating a slight cooling flow. The fits suggest that none of the central galaxies hosts an AGN that contributes significantly to the emission in the ROSAT band (0.1 to 2.4 keV). Using the radial temperature and density distributions, the total gravitating mass within a radius r can be derived. This value is 1.7±0.4 1013 M⊙ within 300 kpc for all three cases, as opposed to to 1014‥15 M⊙ for rich clusters.

Shkh 360 has the characteristic signature of a strongly interacting group. Seven galaxies are embedded in a common extended halo and the isophotes indicate clear signs of alignment in B,V, and R. The parameters of the group as the red shift, z, the distance, d, the projected diameter, D, (basing on H = 55 km/s/Mpc), the virial radius, Rvir, the velocity dispersion, σv, the virial mass, the crossing time, τ, and the space density of galaxies, n, are given in the Table.

In the last two decades several methods have been employed to search for the ancestors of present day galaxies undergoing their first starburst at high redshift, the so-called “primeval galaxies” (PGs). According to predictions of the Ly-α flux from the PG phase current surveys for Ly-α bright PGs should have detected 101 − 103 PGs. Yet, no really good candidate has been found. One possible explanation for this discrepancy would be the presence of dust which could strongly suppress Ly-α. In fact, models of early galaxy formation are able to produce gas to dust ratios of about 1/10 solar after some 108 years. This would suppress the emerging Ly-α flux below current detection limits. Thus, to detect a PG in its Ly-α bright phase, one has to hit exactly the redshift of their first star formation. On the other hand, the epoch of galaxy formation is likely to extend over much longer time. So when searching a finite volume of the universe (given by the depth Δz and the field ΔΩ), the protogalaxies are not simultaniously in the Ly-α bright PG phase and only a fraction of them exceed the detection limit. Our new attempt to predict the expected number of PGs takes this reduced propability into account. Further contraints of the Ly-α luminosity were derived from recent observations and theoretical work (for details see E.Thommes & K.Meisenheimer in Galaxies in the Young Universe, Eds. H.Hippelein et al., Springer-Verlag, 1995, p.242). As expected, we find that the number density of Ly-α emitting PGs is drastically reduced in comparison to previous predictions. Thus previous surveys had no realistic chance to find them. Nevertheless, our calculations also show, that the detection of Ly-α bright PGs is in the scope of present day techniques. Specifically, we predict that the Calar-Alto-Deep-Imaging-Survey (see contribution of H. Hippelein et. al., these proc.) which will search for Ly-α in an area of ≈ 0.3□° down to a limiting line flux of 3 × 10−20W/m2 should detect 10 … 100 PGs in three redshift intervals Δz = 0.1. The uncertainty accounts for our ignorance of q0 and the unknown epoch of galaxy formation.

We present first results of a Hubble Space Telescope imaging and a Palomar and Keck Observatories spectroscopy program of distant, rich galaxy clusters in the form of a “Hubble Atlas” of morphological types at z ≥ 0.75. Two clusters from the compilation of Gunn, Hoessel & Oke (1985) have been studied to date, Cl1322+3027 at z ≈ 0.76 and Cl1603+4313 at z ≈ 0.90.

We performed the high frequency radio studies of spiral galaxies using the 100 m MPIfR radio telescope at 10.55 GHz. Two objects: NGC 4254 and NGC 3627 possess perturbed spiral structures while two others, NGC 3521 and NGC 5055 are flocculent objects, lacking organized spiral patterns. NGC 3521 possesses also a peculiar dust lane. For NGC 4254, NGC 3627 and NGC 5055 deep polarization maps were made, for NGC 3521 the total power data only were analyzed (see Urbanik et al. 1989).

We constrain the growth rate of structure, as represented by the spatial two-point galaxy auto-correlation function, at redshifts where this has not yet been measured directly by combining recent measurements of the amplitude of the angular two-point galaxy auto-correlation, at magnitudes as faint as Vmedian ≤ 25, with new observations of the redshift distribution of very faint galaxies. We show that ξ for the overall galaxy population (at a fixed proper separation r) grows (1 + z)4±1 times as fast as clustering which is fixed in proper coordinates. Even extreme models where “blue” galaxies have a smaller, IRAS-like, correlation function do not reduce the growth rate below (1 + z)2.5±1 times the clustering fixed in proper coordinates (Roukema, B.F. and Valls–Gabaud, D. (1995) A&A, submitted).

The Hubble Space Telescope has discovered a number of ellipticals and S0's with small nuclear, stellar disks (eg. van den Bosch et al. 1994, AJ, 108, 1579). The kinematics of these disks may allow a derivation of the central mass density of the host galaxy, in much the same way as is possible with ionized gas disks (e.g. M87; Harms et al. 1994, ApJ, 435, L35). In order to understand the kinematic signatures of these disks, we have constructed two-integral, axisymmetric models of ellipticals with nuclear stellar disks. We use the method developed by Hunter & Qian (1993, MNRAS, 262, 401) to calculate f(E, Lz ), from which we derive the velocity profiles (VPs). Depending on the choice of the odd part of the DF, one can construct a large variety of models including some with counter-rotating cores.

Measurements of the mass-to-light ratios of galaxies are crucial to a proper understanding of galaxy dynamics, dark matter distributions, and the general matter content of the universe. We report on results of a program to measure the change of the M/L ratio with redshift. Since the evolution of the M/L can be parameterized as

We have developed a new stellar population synthesis model for calculating colours and absorption line indices in early type galaxies. This model can work either for single-age stellar populations or in an evolutionary scheme following the chemical evolution. The model is based on the isochrones of the Padova group and we have developed our own method of conversion to colours. Details can be found in Vazdekis A., Casuso E., Peletier R. & Beckman J. (submitted, 1995). To test the model we have obtained accurate observations in many colours and line indices of the three standard galaxies: NGC 3379, NGC 4472 and NGC 4594.

We performed B and R surface photometry of 92 faint mostly late type galaxies, selected towards three nearby voids (Hopp et al., 1995 A&AS 109, 537). CCD frames were taken with the Calar Alto 3.5m telescope and with the MPIA/ESO 2.2m telescope. We calculated the azimuthally averaged equivalent profiles, asymtotic total magnitudes and colours, and performed ellipse-fitting of isophotes. Observed light profiles were fitted with a power law μ = μ0 + 1.086αr 1/n . About 40% of profiles are pure exponentials (n = 1); 38% of the profiles reveal a bulge/disk or disk/disk composition; 20% of them show central light depression. We classified the nearby galaxies (z ≤ 0.04) as being related either to clusters (11 galaxies), to sheets (23) or to voids (9). The obtained parameters are compared to those of HSB and of LSB field galaxies.

We investigate the scatter in the TF-relations and study the Dark Matter component of spiral galaxies as a function of luminosity, morphology, scale length etc. by means of a detailed kinematic and photometric study of individual galaxies in a cluster. Because all the galaxies are at the same distance there is no doubt about their relative masses and luminosities.

Centaurus A (NGC 5128) is a nearby Giant Elliptical (3.5Mpc, 1012 Solar Masses). It has a prominent dust-lane which has an axis of rotation orientated differently from that of the underlying galaxy. Close to it are two galaxies: NGC 5237 – a dwarf elliptical, and Fourcade-Figueroa – a low surface brightness irregular. We are investigating whether these three objects are the resulting components of a grazing interaction between a Giant Elliptical and a less massive spiral galaxy. We have conducted n-body simulations, modelling all components of the two original interacting galaxies. Preliminary results show that Cen A, its dust-lane, and NGC 5237 are consistent with this simulation model. Centaurus A exhibits many other features which are also indicative of a past interaction.

High-velocity clouds (HVCs) are HI clouds deviating strongly from the general Galactic rotation. Their distances, and hence origins, have long remained unknown. However, three major complexes are now known to lie at z > 1 kpc, while two smaller clouds are closer to the plane (Wakker et al. 1995). These incomplete results still allow a variety of origins.

Investigations of broad band energy distributions of specific classes of sources requires homogeneous samples of a sufficiently large number of objects. Deep and homogeneous surveys in those energy ranges which are accessible to satellites only are rare. One such a field in the north ecliptic pole (NEP). The ROSAT and IRAS whole sky surveys and deep additional observations by other satellites make the NEP the region of the deepest mid-IR and X-ray observations. We performed complete surveys in three optical/IR colors at 460nm, 700nm, and 2.1 μm (B, R, and K′) within a one square degree field around the NEP. Limiting magnitudes in the three bands are 23, 24, and 19, respectively. The optical bands are observed with sufficient spatial sampling to classify extended and point sources. Down to levels which still correspond to high completeness limits we detect 80.000, 240.000 and 25.000 sources in B, R, and K′, respectively.

Our numerical tool is SUPERBOX (Bien et al., 1991) which can treat an arbitrary number of galaxies. Simulations including Black Holes are important to understand recent observations, see e. g. Mediavilla and Arribas (1993).

The James Clerk Maxwell Telescope (JCMT) and the Caltech Submillimeter Observatory (CSO) are located 160m apart on Mauna Kea, Hawaii. Recently they have been linked together to allow the first submillimetre interferometric observations (between 300GHz and 490GHz, soon to 690GHz). Submillimetre observations can be used to probe the physical conditions of molecular clouds and dust in starforming regions. Lines from rotational transitions of molecules such as CO, HCN and HCO+ trace densities, temperatures and masses of molecular gas. The thermal emission of cold dust, typically found in dense clouds, also peaks in the submm regime.

The Lyman and Werner bands of H 2 in interstellar gas provide information about gas temperature, density and the ultraviolet radiation field, and possibly about dust content. This is especially useful for high redshift QSO absorption systems, where usually the only data available arise from absorption lines. We present 25 – 50 km s−1 resolution data taken with the CTIO 4m telescope plus echelle spectrograph of the Lyα forest region of 0528–250, which has a damped Lyα absorption system at z = 2.81. Using a χ2 profile fitting routine (Lanzetta & Bowen 1992. ApJ, 391, 48), we find an H 2 fraction of ∼ 10−2, an order of magnitude below that of Galactic diffuse interstellar clouds. This may be caused by some combination of a less efficient H 2 formation rate or an increased H 2 dissociation rate. Using the relative populations of the J″ = 0, 1 rotational levels, we derive a kinetic temperature of TK = 136 ± 16 K. The total velocity spread as traced by sensitive metal transitions is 250 km s−1, consistent with a highly inclined, rotating ensemble of clouds associated with a luminous spiral galaxy. A representative section of the spectrum is shown below, binned at roughly the Nyquist rate with the χ2 fit to H 2 of the z = 2.8108 absorption system.

We present new results on the morphology of member galaxies in the distant cluster C10016+16 from HST images (WFCl). Based on narrow multiband ground-based photometry and spectra obtained with the Keck 10 m telescope we identify 7 new cluster members which appear to have strong Balmer absorption features but no detectable emission lines, doubling the number of such galaxies previously observed with HST in this cluster. These candidate E+A galaxies have been identified in other distant clusters, but the morphology of this population has appeared bulge-like in AC114 (Couch et al., 1994, ApJ 430, 107) and disk-like or irregular and interacting in C10939+47 and C10016+16 (Wirth et al., 1994 ApJ 435, L105). By means of the image concentration index as a quantitative measure of morphology we show that our enlarged sample of E+A objects in C10016+16 now contains some galaxies resembling bulge systems as well as the previously-identified disk-like objects. The observed heterogeneity suggests that both galaxy mergers (rapidly resulting in an r 1/4 profile) and ram-pressure stripping of isolated late-type systems may originate E+A objects.