Line width distributions as evidence for axisymmetry in the broad line regions of active galaxies

The nuclei of a wide class of active galaxies emit broad emission lines with widths at half maximum (FWHM) in the range $10^{3}-10^{4}$ km s$^{-1}$. This spread of widths is not solely a consequence of the range of the luminosities of these sources since a plot of width versus luminosity shows a large scatter. We propose that the broad line emission region (BLR) is axially symmetric and that this scatter in line width arises from an additional dependence on the angle of the line of sight to the axis of the emission region. Such a relation is natural in unified models of active nuclei which link a variety of observed properties to viewing angle. Adopting a simple form for the line width as a function of luminosity and angle, and convolving this with the observed luminosity function, allows us to predict a line width distribution consistent with the available data. Furthermore, we use the relation between the equivalent width of a line and the luminosity in the continuum (the `Baldwin Effect') to predict an observed correlation between line width and equivalent width. The scatter on this correlation is again provided by angular dependence. The results have applications as diagnostics of models of the broad line emission region and in cosmology.Comment: 8 pages including 4 figures. Accepted for publication in MNRAS Letter

The luminosity dependence of opening angle in unified models of active galaxies

In unified models of active galaxies the direct line of sight to the nucleus is unobscured only within a certain cone of directions. An opening angle for this cone is usually estimated by methods such as the overall ratio of Seyfert 1s to Seyfert2s, the latter assumed to be obscured versions of the former. Here we shall show, as has often been suspected, that the opening angle of the cone depends on the luminosity of the central source, with higher luminosities corresponding to larger opening angles. This conclusion depends only on the assumption that the width of the broad emission lines at a given luminosity is a measure of inclination angle, an assumption that is supported by observation in radio-loud systems. On the other hand we show that the scatter in X-ray spectral index is not primarily an effect of viewing angle, in contrast to what might be expected if the scatter on the spectral index versus luminosity relation were a consequence of absorption in the obscuring material. The observed correlation between linewidth and spectral index appears to be a further consequence of the dependence of opening angle on luminosity.Comment: 8 pages, 7 figures, uses mn.sty. Accepted for publication in MNRA

Determining the cosmological parameters from the linewidths of active galaxies

We have previously shown that the linewidth distribution in AGN can be accounted for by an axisymmetric broad emission line region. In this paper we show that the linewidth distribution changes with redshift and that these changes are dependent on H_0 and q_0. We show that relatively small samples of AGN at high redshift with measured linewidth at half maximum can be used to distinguish between values of H_0 and q_0. Furthermore larger low redshift samples can be used to distinguish between luminosity functions and hence different models of quasar evolution.Comment: Accepted for publication in MNRAS. 8 pages LaTeX, uses mn.st

Atmospheric transmission in the region from 16.75 to 20.95 micrometers

Atmospheric transmission analysis from solar spectrum observations covering 16.75 to 20.95 micrometers region on Bigelow Mountain, Arizon

Moving Detectors in Cavities

We consider two-level detectors, coupled to a quantum scalar field, moving inside cavities. We highlight some pathological resonant effects due to abrupt boundaries, and decide to describe the cavity by switching smoothly the interaction by a time-dependent gate-like function. Considering uniformly accelerated trajectories, we show that some specific choices of non-adiabatic switching have led to hazardous interpretations about the enhancement of the Unruh effect in cavities. More specifically, we show that the emission/absorption ratio takes arbitrary high values according to the emitted quanta properties and to the transients undergone at the entrance and the exit of the cavity, {\it independently of the acceleration}. An explicit example is provided where we show that inertial and uniformly accelerated world-lines can even lead to the same ``pseudo-temperature''.Comment: 13 pages, 6 figures, version accepted in Phys.Rev.

Pollination systems in Namaqualand : a response to a predictable winter rainfall regime

The low abundance and relatively low diversity of anthophilous insects in Namaqualand appears to have resulted in the extensive radiation in floral characters. The paucity of empirical data supporting the notion of pollen limitation, necessitates further research in the pollination ecology of the region. In particular, research should concentrate on finding evidence for a reduction in fruit set resulting from pollen limitation. By furthering our knowledge in this aspect of the ecological functioning of Namaqualand, we might be able to better understand and explain the observed pollination syndromes

The impact of rain water on soil pore networks following irrigation with saline-sodic water

The soil pore network is an important factor affecting soil hydraulic conductivity (Ksat). In this study we examine the effect on the soil pore network of a Red Ferrosol caused by irrigation with good quality irrigation water (GQW), as well as saline-sodic water with varying sodium absorption ratios (SAR; 10, 50 and 120) and constant electrical conductivity (EC; 2 dS m-1), followed by application of distilled water (simulating rain water). The Ksat was measured for the different waters before and after applying the rain water to the soil. Soil samples were taken from different depths (1, 4 and 8 cm) for exchangeable cations measurement and the changes in ESP of the soil. Soil horizontal cross-sections were taken from the first 2 cm of the soil cores after drying with acetone and impregnation with polyester resin mixed with green fluorescent dye catalyst and hardener. These sections were polished and visualized under a microscope to investigate the changes in the soil pore network. By increasing the SAR of the water applied from 0.11 (GQW) to SAR 50 and 120, a significant reduction in Ksat was found, alongside a significant increase in the ESP of the soil from 3 to 10 and 11, respectively; this was most evident near the soil surface. After applying rain water, the Ksat reduced significantly approaching 0 mm h-1 where soil was treated with water of SAR 120. Visualisation of the soil pore network of the treated soils following the application of deionised water clearly showed a reduction in soil macroporosity where water quality of SAR ≥10 was applied, even where soils were non-sodic. Where irrigation occurred with good quality, low SAR water, this reduction was not evident

Radiation Induced Damage in GaAs Particle Detectors

The motivation for investigating the use of GaAs as a material for detecting particles in experiments for High Energy Physics (HEP) arose from its perceived resistance to radiation damage. This is a vital requirement for detector materials that are to be used in experiments at future accelerators where the radiation environments would exclude all but the most radiation resistant of detector types.Comment: 5 pages. PS file only - original in WORD Also available at http://ppewww.ph.gla.ac.uk/preprints/97/06