The X-ray Emission of NGC 1068

This paper summarises the X-ray properties of NGC 1068 from the observers perspective and reports new observations with the ROSAT HRI. Below ? 2 keV, the spectrum is steep and probably represents thermal emission from gas with temperature kT ? 0.1 - 0.6 keV. Above ? 2 keV, the spectrum is much flatter and may be described by a power-law with energy index α ? 0.3. Images with the ROSAT HRI reveal that about half the X-ray flux in the 0.1 - 2.4 keV band is extended on scales > 5″ (360 pc). Recent ROSAT PSPC observations of starburst galaxies show integrated soft X-ray spectra which are very similar to that of NGC 1068 below 2 keV. The spatially extended, steep, soft X-ray emission of NGC 1068 probably originates through thermal emission from a hot wind driven by the disk starburst, the Seyfert nucleus or a combination of the two. On the other hand, the hard emission above 2 keV is almost certainly dominated by the Seyfert nucleus.     

Bridging Political Expectations and Scientific Limitations in Climate Risk Management – On the Uncertain Effects of International Carbon Sink Policies<Superscript>*</Superscript>

Despite great advances in carbon cycle research during the past decade the climatic impact of terrestrial ecosystems is still highly uncertain. Although contemporary studies suggest that the terrestrial biosphere has acted as a net sink to atmospheric carbon during the past two decades, the future role of terrestrial carbon pools is most difficult to foresee. When land use change and forestry activities were included into the Kyoto Protocol in 1997, the requirements for scientific precision increased significantly. At the same time the political expectations of carbon sequestration as climate mitigation strategy added uncertainties of a social kind to the study of land-atmosphere carbon exchange that have been difficult to address by conventional scientific methods. In this paper I explore how the failure to take into account the effects of direct human activity in scientific projections of future terrestrial carbon storage has resulted in a simplified appreciation of the risks embedded in a global carbon sequestration scheme. I argue that the social limits to scientific analysis must be addressed in order to accommodate these risks in future climate governance and to enable continued scientific authority in the international climate regime.     

Calibration of Local Magnitude M<Subscript>L</Subscript> in the Azores Archipelago Based on Recent Digital Recordings

—The development of the digital seismic network in the Azores Archipelago during recent years made it possible to obtain the amplitudes (waveform) of recorded motion in a large set of stations. With this new data, maximum amplitudes of the Wood Anderson seismograph are computed, for each station/component, which, together with epicentral distances, allows for the estimation of local magnitude M _L . We used data recorded in 8 digital permanent three-component stations, with inter-stations distances up to 300 km, in the period June 1998 – June 2000, corresponding to a set of 1315 events with magnitude (M _L or M _D ) 2<M<5.8 and epicenters located in the Azores region, to estimate the coefficients of the equation to compute M _L , as well as to determine the corrections to be applied to each station. The new set of parameters, formed by attenuation coefficients and station corrections, were introduced in the calculations of the M _L , leading to smaller dispersions in the analyzed dataset. We also conclude that the attenuation in the first 150 km is similar to the California values, although higher for longer distances.     

Ar/Ar thermochronology of the Kampa Dome, southern Tibet: Implications for tectonic evolution of the North Himalayan gneiss domes

Structural and thermochronological studies of the Kampa Dome provide constraints on timing and mechanisms of gneiss dome formation in southern Tibet. The core of Kampa Dome contains the Kampa Granite, a Cambrian orthogneiss that was deformed under high temperature (sub-solidus) conditions during Himalayan orogenesis. The Kampa Granite is intruded by syn-tectonic leucogranite dikes and sills of probable Oligocene to Miocene age. Overlying Paleozoic to Mesozoic metasedimentary rocks decrease in peak metamorphic grade from kyanite + staurolite grade at the base of the sequence to unmetamorphosed at the top. The Kampa Shear Zone traverses the Kampa Granite — metasediment contact and contains evidence for high-temperature to low-temperature ductile deformation and brittle faulting. The shear zone is interpreted to represent an exhumed portion of the South Tibetan Detachment System. Biotite and muscovite ⁴⁰Ar/³⁹Ar thermochronology from the metasedimentary sequence yields disturbed spectra with 14.22 ± 0.18 to 15.54 ± 0.39 Ma cooling ages and concordant spectra with 14.64 ± 0.15 to 14.68 ± 0.07 Ma cooling ages. Petrographic investigations suggest disturbed samples are associated with excess argon, intracrystalline deformation, mineral and fluid inclusions and/or chloritization that led to variations in argon systematics. We conclude that the entire metasedimentary sequence cooled rapidly through mica closure temperatures at  14.6 Ma. The Kampa Granite yields the youngest biotite ⁴⁰Ar/³⁹Ar ages of  13.7 Ma immediately below the granite–metasediment contact. We suggest that this age variation reflects either varying mica closure temperatures, re-heating of the Kampa Granite biotites above closure temperatures between 14.6 Ma and 13.7 Ma, or juxtaposition of rocks with different thermal histories. Our data do not corroborate the “inverse” mica cooling gradient observed in adjacent North Himalayan gneiss domes. Instead, we infer that mica cooling occurred in response to exhumation and conduction related to top-to-north normal faulting in the overlying sequence, top-to-south thrusting at depth, and coeval surface denudation.