ALBERT

Notes: [Auszug] The morphologies of the extended emission-line regions around the QSOs 3CR249.1 and Ton202 indicate that they have, in both cases, resulted from interactions between two galaxies of roughly equal mass and that the galaxies involved possessed extensive rotating gaseous disks before their encounters. ...

Notes: [Auszug] The redshift of 4C11.50a itself, determined from the sharp [O III] ??4,959, 5,007 lines, is found to be 0.4358, in good agreement with the value of 0.4359 given by Wampler et al.1. The difference in radial velocity between the QSO and the galaxy, in the local rest frame of the QSO, is 376 km s?1. ...

Notes: [Auszug] A recent survey3 of redshifts of a well-defined sample of galaxies near bright, low-redshift QSOs found 8 out of 27 fields for which at least one galaxy had a redshift matching that of the QSO. The probability that a result of this significance or greater could have occurred by chance was shown ...

Notes: Abstract We describe the current status of two complementary programs to search for objects with strong emission lines in a 300 Å gap, centered at 9150 Å, in the strong airglow emission. Both programs are being carried out with LRIS on the Keck II telescope. The first of these uses broad-band and narrow-band filter photometry to select candidates, followed by multi-slit spectroscopy through the same narrow-band filter to limit the band pass and allow a dense packing of slits. The second uses six parallel long slits to carry out a blind spectroscopic search through the filter isolating the 9150 Å window. The total slit area covered ranges from 1 to 3.5 square arcmin per pointing, depending on slit width, and we can obtain 3 σ detections of emission lines of 〈2 × 10-18 erg cm-2 s-1 in a 12000 s observation with1″5 slits. Because, for faint objects in both programs, we are most sensitive to strong lines with large equivalent widths, most of our detections will be restricted to a few specific emission lines at certain discrete redshifts. One of the more interesting possibilities is Ly-α at z ∼ 6.5. However, even with 12000 s integrations on the Keck II telescope, our narrow-band imaging does not pick up objects with emission-line fluxes ≲10-17 erg cm-2 s-1. With this limit, at z ∼ 6.5, we would pick up only the most luminous of the z 〉 5 objects discovered so far. Our blind spectroscopic search potentially has a better chance of discovering such objects, but we have not yet found any definite examples in the limited area of the sky we have covered to date. We discuss the criteria for identifying Ly-α emission in noisy spectra and emphasize how high-ionization dwarf galaxies at low redshift can be mistaken for Ly-α candidates under certain conditions.

Notes: Abstract The Hubble classification scheme of galaxies is based on their optical appearance or `masks'. As one goes from early to late type spirals, both barred and unbarred, the optical appearance will be dominated more and more by the young Population I, i.e., blue stars and dust. Atlases reveal the rich variety of responses of the Population I component of gas and dust (the mask) to the underlying, older, stellar population. However, the gaseous Population I component, may only constitute 5 percent of the dynamical mass of the galaxy. Masks of negligible mass may conceal the human face – and that of galaxy. In the near-infrared, the morphology of older star-dominated disk indicates a simple classification scheme: the dominant Fourier m-mode in the dust penetrated regime, and the associated pitch angle. A ubiquity of low m=1 and m=2 modes is confirmed. On the basis of deprojected H (1.65 μm) and K′ (2.1μm) images, we propose that the evolved stellar disks may be grouped into three principal dust penetrated archetypes: those with tightly wound stellar arms characterised by pitch angles atK′ of ∼ 10° (the α class),an intermediate group with pitch angles of ∼ 25° (theβ class) and thirdly, those with open spirals demarcated by pitch angles at K′ of∼ 40° (the γ bin). Flat or falling rotation curves give rise to the tightly woundα class; rising rotation curves are associated with the openγ class. The observed dust penetrated classes are inextricably related to the rate of shear in the stellar disk, as determined by A/ω. Here A is the first Oort constant andω denotes the angular velocity. There is no correlation between our dust penetrated classes and optical Hubble binning; the Hubble tuning fork does not constrain the morphology of the old stellar Population II disks. NGC 3223 and NGC 7083 (both SbI-II and almost the same absolute blue magnitude) have identical Hubble types and identical luminosity classes; the dust penetrated disk of NGC3223 has tightly wrapped arms of class α, whereas the near-infrared disk of NGC 7083 has open arms of class γ.This is in turn associated with their very different rotation curve shapes yielding different rates of shear A/ω; in their stellar disks. Any specific dust penetrated archetype may be the resident disk of both an early or late type galaxy. The number of arms and the pitch angle of the arms at K′of the early-type `a' spiral NGC 718 are almost identical to those for the late-type `c' spiral NGC 309. We demonstrate that galaxies on opposite ends of the tuning fork can display remarkably similar evolved disk morphologies and belong to the same dust penetrated class. In this sense, there is no differentiation between a nearly and late type galaxy: the Hubble tuning fork becomes a circle. Furthermore, a proto typically flocculent galaxy such as NGC 5055 (Elmegreen arm class 3) can have an evolved disk morphology almost identical to that of NGC 5861,characterised in the optical as having one of the most regular spiral patterns known and of Elmegreen class 12.Both optically flocculent or grand design galaxies can reside within the same dust penetrated morphological bin. As was suggested by Block et al. (1994a), it is the gas dominated Population I component which determines the optical types (a, b, c). This may be partially or even fully decoupled from the Population II disk. Those L=lopsided galaxies (where m=1 is a dominant mode) are designatedLα, Lβ and Lγ according to the dust penetrated pitch angle; E=evensided galaxies (where m=2 is the dominant Fourier mode) are classified into classes Eα, Eβ andEγ, according to our three principal dust penetrated archetypes. The L and E modes are the most common morphologies in our sample, which spans a range of Hubble types from early (a) to late (irregular).

Notes: Abstract The evidence for the association of QSOs with groups of galaxies and the available data on the global properties of such groups are reviewed. At least for redshifts less than 0.5, QSOs tend to occur in richer-than-average environments. There is some evidence that groups around steep-radio-spectrum QSOs are systematically richer than those around radio-quiet and flat-radiospectrum QSOs. The groups associated with the former may sometimes reach central galaxy number densities similar to those of moderately rich clusters, but are significantly more compact, and there is no evidence that any such groups have velocity dispersions above a few hundred km s−1. A possible explanation for this environmental preference can be found in the recent evidence, from a variety of directions, that galaxy interactions play an important role in triggering nuclear activity. A significant fraction of low-redshift QSOs either have close companions at the same redshift, or show some indication of recent interaction. The results of a recent search for resolvable extended emission around a large sample of luminous low-redshift QSOs are described. There are now substantial reasons for believing that the presence of these extended emission-line regions, which are found around approximately 25% of all low-redshift OSOs, is often a signature of a recent interaction. Observed correlations between radio properties, optical spectra, and environment are mentioned briefly. The present evidence tends to support suggestions that there are two classes of QSOs, one being the extension of the Seyfert population to higher luminosities and having spiral host galaxies, the other being closely related to the broad-line radio galaxies. The host galaxies of this latter class appear often to be morphologically ellipticals, but may in fact be products of recent mergers.