The physical conditions in the BHR71 outflows

Highly-collimated outflows are believed to be the earliest stage in outflow evolution, so their study is essential for understanding the processes driving outflows. The BHR71 Bok globule is known to harbour such a highly-collimated outflow, which is powered by a protostar belonging to a protobinary system. Using the APEX telescope on Chajnantor, we mapped the BHR71 highly-collimated outflow in CO(3-2), and observed several bright points of the outflow in the molecular transitions CO(4-3), CO(7-6), ¹³CO(3-2), C¹⁸O(3-2), CH₃OH(7-6) and H₂CO(4-3). We use an LVG code to characterise the temperature enhancements in these regions. These observations are particularly interesting for investigating the interaction of collimated outflows with the ambient molecular cloud. In our CO(3-2) map, the second outflow driven by IRS2, which is the second source of the binary system, is completely revealed and shown to be bipolar. We also measure temperature enhancements in the lobes. The CO and methanol LVG modelling points to temperatures between 30 and 50 K in the two lobes. The methanol emission in the southern lobe bright knot is barely resolved with the APEX single-dish. ALMA will thus be a central tool to study the shock chemistry in these regions.     

Polarimetric imaging of interacting pairs

We present optical polarization maps of a sample of four interacting pairs at different phases of encounter, from nearly unperturbed galaxies to on‐going mergers. Only the pair RR 24 shows a linear polarization pattern which extends in both galaxies for several kiloparsecs. The more perturbed member, RR 24b, is linearly polarized up to the level of ≈3%. No polarization is measured in the strongly perturbed late‐type pair members of RR 23 and RR 99. Also, in the central part of the double nuclei shell galaxy ESO 2400100 there is no significant polarization. We use the ionized gas velocity field of RR 24 to interpret its linear polarization structure. In RR 24a the quite regular gas kinematics reflect the unperturbed spirallike polarization structure. In RR 24b a strong velocity gradient in ionized gas could be associated with the polarization structure. We suggest that the large‐scale magnetic field of the RR 24 pair members still plays a role in shaping the polarization pattern. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Modelling the cosmological co-evolution of supermassive black holes and galaxies – I. BH scaling relations and the AGN luminosity function

We model the cosmological co-evolution of galaxies and their central supermassive black holes (BHs) within a semi-analytical framework developed on the outputs of the Millennium Simulation. This model, described in detail by Croton et al. and De Lucia and Blaizot, introduces a 'radio mode' feedback from active galactic nuclei (AGN) at the centre of X-ray emitting atmospheres in galaxy groups and clusters. Thanks to this mechanism, the model can simultaneously explain: (i) the low observed mass dropout rate in cooling flows; (ii) the exponential cut-off in the bright end of the galaxy luminosity function and (iii) the bulge-dominated morphologies and old stellar ages of the most massive galaxies in clusters. This paper is the first of a series in which we investigate how well this model can also reproduce the physical properties of BHs and AGN. Here we analyse the scaling relations, the fundamental plane and the mass function of BHs, and compare them with the most recent observational data. Moreover, we extend the semi-analytic model to follow the evolution of the BH mass accretion and its conversion into radiation, and compare the derived AGN bolometric luminosity function with the observed one. While we find for the most part a very good agreement between predicted and observed BH properties, the semi-analytic model underestimates the number density of luminous AGN at high redshifts, independently of the adopted Eddington factor and accretion efficiency. However, an agreement with the observations is possible within the framework of our model, provided it is assumed that the cold gas fraction accreted by BHs at high redshifts is larger than at low redshifts.     

Relating electrical conduction of alluvial sediments to textural properties and pore‐fluid conductivity

Electrical conductivity of alluvial sediments depends on litho‐textural properties, fluid saturation and porewater conductivity. Therefore, for hydrostratigraphic applications of direct current resistivity methods in porous sedimentary aquifers, it can be useful to characterize the prevailing mechanisms of electrical conduction (electrolytic or shale conduction) according to the litho‐textural properties and to the porewater characteristics. An experimental device and a measurement protocol were developed and applied to collect data on eight samples of alluvial sediments from the Po plain (Northern Italy), characterized by different grain‐size distribution, and fully saturated with porewater of variable conductivity. The bulk electrical conductivities obtained with the laboratory tests were interpreted with a classical two‐component model, which requires the identification of the intrinsic conductivity of clay particles and the effective porosity for each sample, and with a three‐component model. The latter is based on the two endmember mechanisms, surface and electrolytic conduction, but takes into account also the interaction between dissolved ions in the pores and the fluid‐grain interface. The experimental data and their interpretation with the phenomenological models show that the volumetric ratio between coarse and fine grains is a simple but effective parameter to determine the electrical behaviour of clastic hydrofacies at the scale of the representative elementary volume.     

Sensitivities of an adjoint, unstructured mesh, tidal model on the European Continental Shelf

Unstructured mesh models can resolve the model domain with a variable and very fine mesh resolution. Nevertheless, tuning the model setup is still required (for example because of parametrized sub-grid processes). Adjoint models are commonly used to calculate sensitivities of ocean models and optimize their parameters so that better agreement is achieved between model simulations and observations. One major obstacle in developing an adjoint model is the need to update the reverse code after each modification of the forward code, which is not always straightforward. Automatic differentiation is a tool to generate the adjoint model code without user input. So far this method has mainly been used for structured mesh ocean models. We present here an unstructured mesh, adjoint, tidal model using this technique, and discuss the sensitivities of the misfit between simulated and observed elevations with respect to open boundary values, the bottom friction coefficient and the bottom topography. The forward model simulates tides on the European Continental Shelf and we show that the tidal model dynamics in the adjoint simulations can be used to define regions, where parameters or mesh has to be optimized. We analyze the dependence of the sensitivities on the wave type and mesh resolution to specify whether the model misfit originates from physical or numerical model deficiencies. In the sensitivity patterns, it is possible to identify islands not resolved in the mesh. We propose to refine the mesh prior to the parameter optimization.     

Persistent polybaric rests of calc-alkaline magmas at Stromboli volcano,Italy: pressure data from fluid inclusions in restitic quartzite nodules

A fluid-inclusion study has been performed on quartzite nodules of stromboli volcano hosted by calc-alkaline lavas of both the Strombolicchio (200 ka) and Paleostromboli II (60 ka) periods. The nodules are mainly composed of quartz crystals with subordinate plagioclase and K-feldspar. Small interstitial minerals such as plagioclase, K-feldspar, clinopyroxene, biotite, and quartz are also found, together with glass. Muscovite, epidote and zircon occur as accessory minerals. Different quartzite nodules occur: (1) equigranular polygonal granoblastic quartzite nodules forming a polygonal texture with clear triple points; (2) inequigranular polygonal granoblastic quartzite nodules; and (3) break-up nodules with strongly resorbed quartz. These quartzites are restites from partial melting, involving felsic crustal rocks at the magma/wall rock contact. Restitic quartz re-crystallises at variable and generally high temperatures, leading to the formation of quartzites with different textures. Quartz grains contain five types of fluid inclusions distinguished on the basis of both fluid type and textural/phase relationships at room temperature. Type I are two-phase (liquid+vapour) CO ₂-rich fluid inclusions. They are primary and subordinately pseudosecondary in origin and have undergone re-equilibration processes. Type II mono-phase/two-phase (vapour/liquid+vapour) CO ₂-rich fluid inclusions are the most common and, based on their spatial distribution and shape, they can be divided into two subclasses: type IIa and type IIb. Type II inclusions are secondary or pseudosecondary and they are assumed to have formed after decrepitation of type I inclusions and cracking of the host quartz. Type III inclusions are mono-phase (vapour); they possibly contain CO ₂ at very low density and surround the inner rims of quartz grains. Type IV two-phase silicate-melt inclusions contain glass±CO ₂-rich fluid. Some of them are cogenetic with type II inclusions. Finally, type V two-phase (liquid+vapour) aqueous inclusions are both vapour-rich and liquid-rich aqueous inclusions. Microthermometric experiments were performed on both type I and II inclusions. Type I inclusions homogenise to liquid between 20 and 30.5 °C. Type IIa inclusions homogenise to vapour in the 24 to 30 °C range, with a maximum peak of frequency at 29 °C. Type IIb inclusions also homogenise to vapour between 14 and 25 °C. There appears to be no difference in homogenisation temperature distribution between the Strombolicchio and Paleostromboli II samples. The trapping pressures of the fluid inclusions have been obtained by combining the microthermometric data of the Strombolicchio and Paleostromboli II samples with the pressure–temperature–volume (i.e. density) characteristics for a pure CO ₂ system. The data on the early inclusions (type I) suggest an important magma rest at a pressure of about 290 MPa (i.e. about 11-km depth). Type IIa CO ₂ inclusions suggest that a second magma rest occurred at a pressure of about 100 MPa (i.e. about 3.5-km depth), whereas type IIb inclusions were trapped later at a shallower depth during the final magma upwelling. No pressure/depth differences seem to occur between the Strombolicchio and Paleostromboli II periods, indicating the same polybaric rests for the calc-alkaline magmas of Stromboli, despite their significantly different ages. This persistence in magma stagnation conditions from 200 to 60 ka suggests a similar plumbing system for the present-day Strombolian activity.     

Study of the outer galactic structure for 288°≤l≤310°, −7°≤b≤2°

The structure of the outer part of the Galaxy is studied, based upon 21-cm line observations of Hi in the region 288°l310°, –7°b2°.In this longitude range the galactic plane is strongly bend toward negative latitudes.The principal outer structure is a spiral arm which has a pitch angle of 10° and is formed by several concentrations differing in shape and size. There exists also a secondary concentration which could be a split from the previous structure.Possible hypotheses about the origin of the later feature are discussed.     

Organochlorine compounds in tissues of swordfish (Xiphias gladius) from Mediterranean Sea and Azores islands

Polychlorobiphenyls (PCB) and organochlorine (OC) pesticides are endocrine-disrupting chemicals (EDCs). The Italian Ministry of Environment has undertaken a program (1999-2001) to measure levels of contaminants in top marine predators and to develop sensitive biomarkers for the evaluation of toxicological risk in these species. In 1999, 15 swordfishes (Xiphias gladius) taken from the Mediterranean Sea along the Sicilian coast (Strait of Messina, Italy) and in the Atlantic Ocean along the Azores Islands, and analysed for 34 congeners of PCBs and 27 organochlorine (OC) pesticides in gonad, muscle, liver and blubber tissues. In the tissues of Mediterranean swordfishes the sum of the determined PCBs congeners ranged from 4.61 to 4651.17 ng g(-1) on fresh tissue basis. Among organochlorine pesticides DDE, DDT and DDD (TDE) predominated with an overall range of 2.37-4734.56 ng(-1) w.w. In particular p,p'-DDE had concentrations appearing up to 3900 ng(-1), with the highest values found in fatty tissues, such as blubber. In the liver of Azores Island swordfishes lower levels of summation PCBs (8.43-294.17 ng/g w.w.) and summation DDTs (<0.01-217.44 ng/g w.w.) were determined.     

Le domaine Tariquide (arc de Gibraltar,Espagne et Maroc) : succession sédimentaire et événements structuraux au Lias et au Dogger

The Lias–Dogger successions of the Tariquide units in the Gibraltar Arc differ from the series of tectonically adjacent units, the Penibetic (Iberia margin) and the Limestone ‘Dorsale’ (Alboran Domain). Lower Lias limestones are eroded and covered by the Domerian, which starts by deposits of open sea, continuous up to the Dogger (J. Musa-type successions), and elsewhere (Los Pastores-type successions) by a thin series (Upper Lias to Upper Dogger), starting by a manganesiferous episode (Ras Leona) and including marls deposited into three episodes, dated by calcareous nannofossils. Faulting events occurred before the Domerian and during the Late Toarcian (Los Pastores). To cite this article: M. Durand-Delga et al., C. R. Geoscience 337 (2005).