Late Weichselian sea level changes at Sotra, Hordaland, western Norway

Sediments from twenty-eight basins were surveyed; ten of these basins with a representative lithostrati-gfaphy wee studied to determine their isolation from the sea during Late Weichselian. Diatom analysis was used to determine salinity changes, which were dated by pollen analysis and the radiocarbon method. The area was deglaciated in the early Boiling, and a regression of about 5 m followed. A transgression of more than 10 m started in late Boiling and terminated in middle Younger Dryas, with a transgression maximum between 38.2 and 40 m above present sea level. All the investigated basins were finally isolated in late Younger Dryas/early Preboreal, during a rapid regression. Repeated cycles of chinophilous/ chinophobous plant communities in the area reflect climatic changes in the period. No evidence of an Older Dryas ice readvance was found.     

DETERMINATION OF WATER IN NINETEEN USGS GEOCHEMICAL REFERENCE STANDARDS USING COULOMETRY AND NEUTRON-CAPTURE PROMPT GAMMA-RAY SPECTROSCOPY

Nineteen USGS GRSs were analyzed with a Dupont 903-H Moisture Analyzer at 110°C and 1000°C to obtain H₂O-and H₂O⁺, and by thermal neutron induced gamma-ray spectrometry to obtain total H₂O. The values are compared with the current literature and the two techniques evaluated. Except for QLO-1 by coulometry, no significant differences were obtained when the results were compared to the the literature.     

Diffuse X-ray emission from late-type galaxy haloes

Current theories of galaxy formation predict that spiral galaxies are embedded in a reservoir of hot gas. This gas is able to cool on to the galaxy, replenishing cold gas that is consumed by star formation. Estimates of the X-ray luminosity emitted in the cooling region suggest a bolometric luminosity of the order of 10×10⁴¹ erg s⁻¹ in massive systems. We have used ROSAT PSPC data to search for extended X-ray emission from the haloes of three nearby, massive, late-type galaxies: NGC 2841, 4594 and 5529. We infer 95 per cent upper limits on the bolometric X-ray luminosities of the haloes of NGC 2841, 4594 and 5529 of 0.4, 1.2 and 3.8×10⁴¹ erg s⁻¹ respectively. Thus, the true luminosity lies well below the straightforward theoretical prediction. We discuss this discrepancy and suggest a number of ways in which the theoretical model might be brought into agreement with the observational results. A possible solution is that the gravitational potentials of the dark matter haloes of these galaxies are weaker than assumed in the current model. Alternatively, the present-day accretion may be substantially less than is required on average to build the disc over the Hubble time. Our results are, however, based on only three galaxies, none of which is ideal for this kind of study. A larger data set is required to explore this important problem further.     

Galaxy bimodality versus stellar mass and environment

We analyse a   z < 0.1  galaxy sample from the Sloan Digital Sky Survey focusing on the variation in the galaxy colour bimodality with stellar mass     and projected neighbour density Σ, and on measurements of the galaxy stellar mass functions. The characteristic mass increases with environmental density from about  10^10.6  to     (Kroupa initial mass function,   H ₀= 70  ) for Σ in the range  0.1–10 Mpc⁻²  . The galaxy population naturally divides into a red and blue sequence with the locus of the sequences in colour–mass and colour–concentration indices not varying strongly with environment. The fraction of galaxies on the red sequence is determined in bins of 0.2 in  log Σ  and     bins). The red fraction   f _r   generally increases continuously in both Σ and     such that there is a unified relation:     . Two simple functions are proposed which provide good fits to the data. These data are compared with analogous quantities in semi-analytical models based on the Millennium N -body simulation: the Bower et al. and Croton et al. models that incorporate active galactic nucleus feedback. Both models predict a strong dependence of the red fraction on stellar mass and environment that is qualitatively similar to the observations. However, a quantitative comparison shows that the Bower et al. model is a significantly better match; this appears to be due to the different treatment of feedback in central galaxies.     

Linear and Circular Polarization from Sagittarius A* and M81*

We describe recent results for Sgr A*, M81* and other low luminosity active galactic nuclei. We have conducted linear and circular polarimetry over a frequency range of 1.4 to 230 GHz and detected a variety of phenomena. The polarization properties of the studied sources are substantially different from higher powered AGN. In the case of Sgr A*, we are able to eliminate ADAFs and Bondi-Hoyle flows as possible models based on mm λ polarimetry. Our success with Sgr A* demonstrates that we can learn about the nature of accretion and outflow in these sources with unprecedented detail. We may also develop probes of general relativity in the strong-field limit.     

The colour–magnitude relation for galaxies in the Coma cluster

We present a new photometric catalogue of the Coma galaxy cluster in the Johnson U and V bands. We cover an area of 3360 arcmin² of sky, to a depth of     in a 13-arcsec diameter aperture, and produce magnitudes for ∼1400 extended objects in metric apertures from 8.8- to 26-arcsec diameters. The mean internal rms scatter in the photometry is 0.014 mag in V , and 0.026 mag in U , for     .
We place new limits on the levels of scatter in the colour–magnitude relation (CMR) in the Coma cluster, and investigate how the slope and scatter of the CMR depend on galaxy morphology, luminosity and position within the cluster. As expected, the lowest levels of scatter are found in the elliptical galaxies, while the late-type galaxies have the highest numbers of galaxies bluewards of the CMR. We investigate whether the slope of the CMR is an artefact of colour gradients within galaxies, and show that it persists when the colours are measured within a diameter that scales with galaxy size. Looking at the environmental dependence of the CMR, we find a trend of systematically bluer galaxy colours with increasing projected radius from the centre of the cluster. Surprisingly, this is accompanied by a decreased scatter of the CMR. We investigate whether this gradient could be caused by dust in the cluster potential, however the reddening required would produce too large a scatter in the colours of the central galaxies. The gradient appears to be better reproduced by a gradient in the mean galactic ages with projected radius.