A Spectropolarimetric Atlas of Seyfert 1 Galaxies

We present optical spectropolarimetry of the nuclei of 36 Seyfert 1 galaxies, obtained with the William Herschel and the Anglo-Australian Telescopes from 1996 to 1999. In 20 of these, the optical emission from the active nucleus is intrinsically polarized. We have measured a significant level of polarization in a further 7 objects but these may be heavily contaminated by Galactic interstellar polarization. The intrinsically polarized Seyfert 1s exhibit a variety of characteristics, with the average polarization ranging from < 0.5 to 5 per cent and many showing variations in both the degree and position angle of polarization across the broad H alpha emission line. We identify a small group of Seyfert 1s that exhibit polarization properties similar to those of Seyfert 2 galaxies in which polarized broad-lines have been discovered. These objects represent direct observational evidence that a Seyfert 2-like far-field polar scattering region is also present in Seyfert 1s. Several other objects have features that can be explained in terms of equatorial scattering of line emission from a rotating disk. We propose that much of the diversity in the polarization properties of Seyfert galaxies can be understood in terms of a model involving both equatorial and polar scattering, the relative importance of the two geometries as sources of polarized light being determined principally by the inclination of the system axis to the line-of-sight.Comment: Accepted for publication in MNRAS (28 pages, 25 figures

Site Characterization Using Integrated Imaging Analysis Methods on Satellite Data of the Islamabad, Pakistan, Region

We develop an integrated digital imaging analysis approach to produce a first-approximation site characterization map for Islamabad, Pakistan, based on remote-sensing data. We apply both pixel-based and object-oriented digital imaging analysis methods to characterize detailed (1:50,000) geomorphology and geology from Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) satellite imagery. We use stereo-correlated relative digital elevation models (rDEMs) derived from ASTER data, as well as spectra in the visible near-infrared (VNIR) to thermal infrared (TIR) domains. The resulting geomorphic units in the study area are classified as mountain (including the Margala Hills and the Khairi Murat Ridge), piedmont, and basin terrain units. The local geologic units are classified as limestone in the Margala Hills and the Khairi Murat Ridge and sandstone rock types for the piedmonts and basins. Shear-wave velocities for these units are assigned in ranges based on established correlations in California. These ranges include Vs30-values to be greater than 500 m/sec for mountain units, 200–600 m/sec for piedmont units, and less than 300 m/sec for basin units. While the resulting map provides the basis for incorporating site response in an assessment of seismic hazard for Islamabad, it also demonstrates the potential use of remote-sensing data for site characterization in regions where only limited conventional mapping has been done

Spectropolarimetry of the 3.4 micron absorption feature in NGC 1068

In order to test the silicate-core/organic-mantle model of galactic interstellar dust, we have performed spectropolarimetry of the 3.4 micron C-H bond stretch that is characteristic of aliphatic hydrocarbons, using the nucleus of the Seyfert 2 galaxy, NGC 1068, as a bright, dusty background source. Polarization calculations show that, if the grains in NGC 1068 had the properties assigned by the core-mantle model to dust in the galactic diffuse ISM, they would cause a detectable rise in polarization over the 3.4 micron feature. No such increase is observed. We discuss modifications to the basic core-mantle model, such as changes in grain size or the existence of additional non-hydrocarbon aligned grain populations, which could better fit the observational evidence. However, we emphasize that the absence of polarization over the 3.4 micron band in NGC 1068 - and, indeed, in every line of sight examined to date - can be readily explained by a population of small, unaligned carbonaceous grains with no physical connection to the silicates.Comment: ApJ, accepte

Rates of convergence for empirical spectral measures: a soft approach

Understanding the limiting behavior of eigenvalues of random matrices is the central problem of random matrix theory. Classical limit results are known for many models, and there has been significant recent progress in obtaining more quantitative, non-asymptotic results. In this paper, we describe a systematic approach to bounding rates of convergence and proving tail inequalities for the empirical spectral measures of a wide variety of random matrix ensembles. We illustrate the approach by proving asymptotically almost sure rates of convergence of the empirical spectral measure in the following ensembles: Wigner matrices, Wishart matrices, Haar-distributed matrices from the compact classical groups, powers of Haar matrices, randomized sums and random compressions of Hermitian matrices, a random matrix model for the Hamiltonians of quantum spin glasses, and finally the complex Ginibre ensemble. Many of the results appeared previously and are being collected and described here as illustrations of the general method; however, some details (particularly in the Wigner and Wishart cases) are new. Our approach makes use of techniques from probability in Banach spaces, in particular concentration of measure and bounds for suprema of stochastic processes, in combination with more classical tools from matrix analysis, approximation theory, and Fourier analysis. It is highly flexible, as evidenced by the broad list of examples. It is moreover based largely on "soft" methods, and involves little hard analysis

The Alternative for Germany’s radicalization in historical-comparative perspective

This article chronicles the AfD’s rightward repositioning and compares it with the programmatic development of three postwar German parties on the ideological wings. By highlighting factors that tilt the balance of power away from moderate reformers towards hardliners, this comparative analysis sheds light on the conditions that lead a relatively successful party on the ideological wings, such as the AfD, to radicalize its programme. Four variables stand out: whether party hardliners take the blame for the recent election loss; whether they offer a convincing programmatic and strategic alternative to the reformers; whether changes in party composition strengthen hardliners; and whether external factors enhance their weight within the party. The essay concludes that the AfD’s radicalization was unusual, but not exceptional. It is however too early to conclude that the Federal Republic’s distinctive institutions and political culture no longer impose significant costs on parties that shift their programmes away from the centre

Supplemented low-protein diets : are they superior in chronic renal failure?

CITATION: Herselman, M. G. et al 1995. Supplemented low-protein diets : are they superior in chronic renal failure? South African Medical Journal, 85(5):361-365.The original publication is available at http://www.samj.org.zaTwenty-two patients with chronic renal failure were randomly assigned to a conventional low-protein diet containing 0,6g protein/kg/day or a very-low-protein diet containing 0,6g protein/kg/day supplemented with essential amino acids; they were followed up for 9 months. There were no significant changes in body mass index, arm muscle area, percentage body fat, serum albumin and transferrin levels in any of the groups; neither was there any difference between the groups in respect of these parameters. Renal function, as measured by the reciprocal of serum creatinine over time, stabilised in both groups during intervention, with no significant difference between the groups. There was however no correlation between changes in renal function and changes in blood pressure, or dietary intake of protein, phosphorus, cholesterol, polyunsaturated and saturated fatty acids. There were also no significant changes and no significant differences between the groups in serum levels of parathyroid hormone and alkaline phosphatase, urine cyclic adenosine monophosphate, tubular reabsorption of phosphate, and the theoretical renal threshold for phosphate. The results of this study suggest that the supplemented very-low-protein diet was not superior to the conventional low-protein diet in terms of its effect on protein-energy status, renal function and biochemical parameters of renal osteodystrophy.Publisher’s versio

Gravitational-Wave Stochastic Background Detection with Resonant-Mass Detectors

In this paper we discuss how the standard optimal Wiener filter theory can be applied, within a linear approximation, to the detection of an isotropic stochastic gravitational-wave background with two or more detectors. We apply then the method to the AURIGA-NAUTILUS pair of ultra low temperature bar detectors, near to operate in coincidence in Italy, obtaining an estimate for the sensitivity to the background spectral density of $\simeq 10^{-49}\ Hz^{-1}$, that converts to an energy density per unit logarithmic frequency of$\simeq 8\times10^{-5}\times\rho_c$with$\rho_c\simeq1.9 \times 10^{-26}\ kg/m^3$the closure density of the Universe. We also show that by adding the VIRGO interferometric detector under construction in Italy to the array, and by properly re- orienting the detectors, one can reach a sensitivity of$\simeq 6 \times10^{-5}\times\rho_c$. We then calculate that the pair formed by VIRGO and one large mass spherical detector properly located in one of the nearby available sites in Italy can reah a sensitivity of$\simeq 2\times10^{-5}\times \rho_c$while a pair of such spherical detectors at the same sites of AURIGA and NAUTILUS can achieve sensitivities of$\simeq 2 \times10^{-6}\rho_c$.Comment: 32 pages, postscript file, also available at http://axln01.lnl.infn.it/reports/stoch.htm