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J. Bland-Hawthorn S.L. Lumsden G.M. Voit G.N. Cecil J.C. Weisheit 《Astrophysics and Space Science》1997,248(1-2):177-190
The radio jet axis of NGC 1068 is characterised by energetic activity from x-ray to radio wavelengths. Detailed kinematic
and polarization studies have shown that this activity is confined to bipolar cones centered on the AGN which intersect the
plane of the disk. Thus, molecular clouds at 1 kpc distance along this axis are an important probe of the nuclear ionizing
luminosity and spectrum. Extended 10.8μm emission coincident with the clouds is reasonably understood by dust heated to high
temperatures by the nuclear radiation field. This model predicts that the nuclear spectrum is quasar-like (power law + blue
excess) with a luminosity 2-5 times higher than inferred by Pier et al. (1994). Consequently, there is little or no polyaromatic
hydrocarbon (PAH) emission associated with the radio-axis molecular clouds. We review this model in the light of new observations.
A multi-waveband collage is included to illustrate the possible orientations of the double cones to our line of sight and
the galaxian plane.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
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V. A. Avramenko S. Yu. Bratskaya A. S. Yakushevich A. V. Voit V. V. Ivanov S. I. Ivannikov 《Geochemistry International》2012,50(5):437-446
Brown coals with high Au and PGE concentrations from six deposits in the southern Russian Far East were analyzed for elemental
composition, acid-base properties, and the molecular-size distribution of humic acids (HA). The ash contents of the coals
were determined to be negatively correlated with their Au concentrations, and the content of “organic Au” (which is chemically
bound to humic substances, HS) reaches 95%. The most probable mode of Au occurrence in the brown coals is submicrometer-sized
particles of elemental gold stabilized by HA. Quantum-mechanical calculations of interactions between Au(0) clusters with
model HS fragments confirm that HS could be originally strongly chemically adsorbed on the surface of elemental gold particles.
Different stability of colloids during centrifuging of alkali extracts of the gold-bearing brown coals was proved to be likely
responsible for the selective separation of free HA and those bound with gold particles, and this can be used to develop a
technology for gold recovery from coals without decomposing their organic matrix. 相似文献
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Mathur S Green PJ Arav N Brotherton M Crenshaw M deKool M Elvis M Goodrich RW Hamann F Hines DC Kashyap V Korista K Peterson BM Shields JC Shlosman I van Breugel W Voit M 《The Astrophysical journal》2000,535(2):L79-L82
We present results of new ASCA observations of the low-luminosity active galactic nucleus (LLAGN) NGC 4579 obtained on 1998 December 18 and 28, and we report on the detection of variability of an iron K emission line. The X-ray luminosities in the 2-10 keV band for the two observations are nearly identical (LX approximately 2x1041 ergs s(-1)), but they are approximately 35% larger than that measured in 1995 July by Terashima et al. An Fe K emission line is detected at 6.39+/-0.09 keV (source rest frame), which is lower than the line energy 6.73+0.13-0.12 keV in the 1995 observation. If we fit the Fe lines with a blend of two Gaussians centered at 6.39 and 6.73 keV, the intensity of the 6.7 keV line decreases, while the intensity of the 6.4 keV line increases, within an interval of 3.5 yr. This variability rules out thermal plasmas in the host galaxy as the origin of the ionized Fe line in this LLAGN. The detection and variability of the 6.4 keV line indicates that cold matter subtends a large solid angle viewed from the nucleus and that it is located within approximately 1 pc from the nucleus. It could be identified with an optically thick standard accretion disk. If this is the case, a standard accretion disk is present at the Eddington ratio of Lbol/LEdd approximately 2x10-3. A broad disk-line profile is not clearly seen, and the structure of the innermost part of accretion disk remains unclear. 相似文献
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The large-scale ( approximately 100 kpc) environments of Seyfert galaxies are not significantly different from those of non-Seyfert galaxies. In the context of the interaction model of the formation of active galactic nuclei (AGNs), it has thus been proposed that AGNs form via "minor mergers" of large disk galaxies with smaller companions. We test this hypothesis by comparing the nuclear spectra of 105 bright nearby galaxies with measurements of their R- or r-band morphological asymmetries at three successive radii. We find no significant differences between these asymmetries among the 13 Seyfert galaxies in the sample and galaxies having other nuclear spectral types (absorption, H ii region-like, LINER), nor is there strong qualitative evidence that such mergers have occurred among any of the Seyfert galaxies or LINERs. Thus, either any minor mergers began greater, similar1 Gyr ago and are essentially complete, or they did not occur at all, and AGNs form independently of any type of interaction. Support for the latter interpretation is provided by the growing evidence that supermassive black holes exist in the cores of most elliptical and early-type spiral galaxies, which in turn suggests that nuclear activity represents a normal phase in the evolution of the bulges of massive galaxies. Galaxy mergers may increase the luminosity of Seyfert nuclei to the level of QSOs, which could explain why the latter objects appear to be found in rich environments and in interacting systems. 相似文献
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Dr. H. Voit 《Pure and Applied Geophysics》1949,15(1-2):90-110
Zusammenfassung Es wird die Frage behandelt: Wie sind beim Bifilargravimeter die Apparatkonstanten und die Abmessungen des Instruments zu wählen, damit die Empfindlichkeitsfunktion (Abhängigkeit der Empfindlichkeit vom Ausschlag) besonders günstig wird? Die Empfindlichkeitsfunktion soll möglichst hoch über der Abszisse möglichst flach verlaufen. Die theoretischen Bedingungen für die beste Dimensionierung werden abgeleitet und die Möglichkeiten für eine praktische Verwirklichung aufgewiesen.
Summary Question concerning the bifilar gravimeter: How have we to choose the constants of the apparatus and the dimensions of the instrument in order to promote the function of sensibility (that is to say sensibility depending upon deflection) as far as possible. The function of sensibility should have the most even flowing possible, as high as possible above the abcissa. The theoretical conditions for the best dimesions are derived and the possibility of a practical realisation is demonstrated.相似文献
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