Probing the 2D kinematic structure of early-type galaxies out to three effective radii

We detail an innovative new technique for measuring the two-dimensional (2D) velocity moments (rotation velocity, velocity dispersion and Gauss–Hermite coefficients h ₃ and h ₄) of the stellar populations of galaxy haloes using spectra from Keck DEIMOS (Deep Imaging Multi-Object Spectrograph) multi-object spectroscopic observations. The data are used to reconstruct 2D rotation velocity maps.
Here we present data for five nearby early-type galaxies to ∼three effective radii. We provide significant insights into the global kinematic structure of these galaxies, and challenge the accepted morphological classification in several cases. We show that between one and three effective radii the velocity dispersion declines very slowly, if at all, in all five galaxies. For the two galaxies with velocity dispersion profiles available from planetary nebulae data we find very good agreement with our stellar profiles. We find a variety of rotation profiles beyond one effective radius, i.e. rotation speed remaining constant, decreasing and increasing with radius. These results are of particular importance to studies which attempt to classify galaxies by their kinematic structure within one effective radius, such as the recent definition of fast- and slow-rotator classes by the Spectrographic Areal Unit for Research on Optical Nebulae project. Our data suggest that the rotator class may change when larger galactocentric radii are probed. This has important implications for dynamical modelling of early-type galaxies. The data from this study are available on-line.     

Li production in the big bang

Li abundance is determined for 23 halo subdwarfs. About half of the stars show [Fe/H] < −1.4 and a space velocityV > 160 km s⁻¹ Li appears to be present in all our halo stars, with an abundance within about ± 0.2 dex of the value logn (Li) = 2.0 found by Spite & Spite (1982). Thus our results provide confirmation of the main conclusion of Spite & Spite.     

Forensic geology in serious crime investigation

CSI, Silent Witness , and a host of other recent television dramas have highlighted the role of science in serious crime investigation and detection. Although many 'real' forensic scientists wince at the media portrayal of their discipline, the programmes have led to a wider understanding of the role of different branches of science in criminal investigations. This is not always a good thing, as 'career' or 'professional' criminals will work very hard at being forensically aware to avoid detection, hence any credible forensic scientist might want to be at best a little reticent as to what they do and how they do it. However, in the UK court system evidence presented by the Prosecution team has to be disclosed to the defence and to be open to challenge in court. This article aims to show, in the broadest of terms, how geology is becoming used increasingly in the detection of serious crime.     

Langmuir-wave conversion as the explanation of moving type IV solar meter-wave radio outbursts

The properties of moving type IV solar radio outbursts observed with the Culgoora radioheliograph and radiospectrograph suggest that these outbursts - even those which rise to great coronal heights - originate through Langmuir-wave conversion. This implies that coronal densities are sometimes greatly enhanced.     

Aorounga and Gweni Fada impact structures,Chad: Remote sensing,petrography, and geochemistry of target rocks

Abstract— Shuttle Radar Topography Mission data was used to investigate the Aorounga and Gweni Fada impact structures in Chad as part of a new remote sensing study. We believe the results of various data treatments provide extensive new perspective on the macro‐structural and topographic divisions for these two impact structures. Our remote sensing studies indicate revised diameters of Aorounga and Gweni Fada of 16 and 22 km, respectively. We selected samples from these two structures for their petrographic, geochemical, and Rb‐Sr and Sm‐Nd isotopic characteristics. In samples from both structures, evidence for shock metamorphism was found in the form of single or multiple sets of planar deformation features in quartz, which confirms the impact origin for both the Aorounga and Gweni Fada structures. The crystallographic orientations of PDFs indicate maximum shock levels of 20–30 GPa for samples from the central parts of both structures. The PDF orientations are characteristic for the orientations observed elsewhere in shocked sandstones, with the higher angles in the orientation histograms being fairly abundant. Geochemically, the rocks are typical upper‐crustal sandstones.     

The effects of seasonal variability and weather on microbial fecal pollution and enteric pathogens in a subtropical estuary

The Charlotte Harbor estuary in southwest Florida was sampled monthly for one year at twelve stations, in the lower reaches of the Myakka and Peace Rivers. The objectives of the study were to address the distribution and seasonal changes in microbial indicators and human pathogen levels in Charlotte Harbor shellfish and recreational waters, and to determine those factors that may be important in the transport and survival of pathogens. Monthly water samples and quarterly sediment samples were analyzed for fecal coliform bacteria, enterococci,Clostridium perfringens, and coliphage. Quarterly samples also were analyzed for the enteric human pathogens,Cryptosporidium spp.,Giardia spp., and enteroviruses. Fecal indicator organisms were generally concentrated in areas of low salinity and high densities of septic systems; however, pollution became widespread during wet weather in, the late fall and winter of 1997–1998, coincident with a strong El Nino event. Between, December 1997 and February 1998, enteroviruses were detected at 75% of the sampling stations; none were detected in other months. Enteric protozoa were detected infrequently and were not related to seasonal influences. Fecal indicators and enteroviruses were each significantly associated with rainfall, streamflow, and temperature. Regression models suggest that temperature and rainfall can predict the occurrence of enteroviruses in 93.7% of the cases. Based on findings in this watershed, factors such as variability in precipitation, streamflow, and temperature show promise in modeling and forecasting periods of poor coastal water quality.     

Identifying impact events within the lunar cataclysm from Ar–Ar ages and compositions of Apollo 16 impact melt rocks

Lunar impact melt breccias provide a unique record of the timing and frequency of collisional events during the early history of the inner Solar System prior to the development of a significant rock record on Earth. The predominance of ages clustering between 3.8 and 4.0 Ga was a major, unexpected discovery obtained from geochronological studies of lunar impact melts, and is the basis of the concept that a cataclysmic bombardment of large planetesimals struck the Earth and Moon, and possibly the entire inner Solar System, about 3.85 ± 0.10 billion years ago. As a test of the cataclysm hypothesis, we measured high-resolution (20–50 steps) ⁴⁰Ar–³⁹Ar age spectra on 25 samples of Apollo 16 impact melt breccias using a continuous laser heating system on sub-milligram fragments. Twenty-one of these 25 breccias produced multi-step plateaus that we interpret as crystallization ages, with 20 of these ages falling in the range 3.75–3.96 Ga. We propose that at least four different melt-producing impact events can be distinguished based on the ages, bulk compositions, and petrographic characteristics of Apollo 16 melt breccias. The recognition of multiple impact events within the Apollo 16 melt breccia suite shows that numerous impact events occurred on the lunar surface within a relatively narrow time interval, providing additional evidence of a heavy bombardment of the Moon during the early Archean.     

Liquid water uptake in unconfined Callovo Oxfordian clay-rock studied with neutron and X-ray imaging

The Callovo Oxfordian clay-rock (COx) is studied in France for the disposal of radioactive waste, because of its extremely low permeability. This host rock is governed by a hydromechanical coupling of high complexity. This paper presents an experimental study into the mechanisms of water uptake in small, unconfined, prismatic specimens of COx, motivated by the comprehension of cracking observed during concrete/COx interface sample preparation. Water uptake is monitored using both X-ray tomography and neutron radiography, the combination of these imaging techniques allowing material deformation and water arrival to be quantified, respectively. Given the speed of water entry and crack propagation, relatively fast imaging is required: 5-min X-ray tomographies and 10-s neutron radiographs are used. In this study, pairs of similar COx samples from the same core are tested separately with each imaging technique. Two different orientations with respect to the core are also investigated. Analysis of the resulting images yields with micro- and macro-scale insights into hydromechanical mechanisms to be obtained. This allows the cracking to be interpreted as a rapid breakdown in capillary suction (supposed large both to drying and rebound from in situ stress state) due to water arrival, which in turn causes a loss of effective stress, allowing cracks to propagate and deliver water further into the material.

     

Direct shear testing of polished slickensided surfaces

A series of ring shear and direct shear tests were performed to measure the drained residual strength of three clay soils. For each of the soils, slickensided direct shear specimens were prepared by wire-cutting intact specimens, and polishing the resulting shear plane on a variety of surfaces to align the clay particles in the direction of shear. Drained direct shear tests were then conducted on each of the polished specimens. The resulting shear strengths were compared with the residual strengths measured in the ring shear device to evaluate the effectiveness of the different polishing techniques for creating slickensided surfaces. Test results indicated that the measurement of residual strengths along preformed slickensided surfaces is extremely sensitive to both the soil type and the slickenside preparation technique that is used. Consequently, this approach does not appear to be a viable alternative to conventional repeated direct shear or ring shear tests to measure residual shear strengths.