A catalogue and analysis of local galaxy ages and metallicities

We have assembled a catalogue of relative ages, metallicities and abundance ratios for about 150 local galaxies in field, group and cluster environments. The galaxies span morphological types from cD and ellipticals, to late-type spirals. Ages and metallicities were estimated from high-quality published spectral line indices using Worthey & Ottaviani (1997) single stellar population evolutionary models.
The identification of galaxy age as a fourth parameter in the fundamental plane ( Forbes, Ponman & Brown 1998 ) is confirmed by our larger sample of ages. We investigate trends between age and metallicity, and with other physical parameters of the galaxies, such as ellipticity, luminosity and kinematic anisotropy. We demonstrate the existence of a galaxy age–metallicity relation similar to that seen for local galactic disc stars, whereby young galaxies have high metallicity, while old galaxies span a large range in metallicities.
We also investigate the influence of environment and morphology on the galaxy age and metallicity, especially the predictions made by semi-analytic hierarchical clustering models (HCM). We confirm that non-cluster ellipticals are indeed younger on average than cluster ellipticals as predicted by the HCM models. However we also find a trend for the more luminous galaxies to have a higher [Mg/Fe] ratio than the lower luminosity galaxies, which is opposite to the expectation from HCM models.     

The early-type galaxies NGC 1407 and NGC 1400 – I. Spatially resolved radial kinematics and surface photometry

This is the first paper of a series focused on investigating the star formation and evolutionary history of the two early-type galaxies NGC 1407 and NGC 1400. They are the two brightest galaxies of the NGC 1407 (or Eridanus-A) group, one of the 60 groups studied as part of the Group Evolution Multi-wavelength Study.
Here, we present new high signal-to-noise ratio long-slit spectroscopic data obtained at the ESO 3.6-m telescope and high-resolution multiband imaging data from the Hubble Space Telescope /Advanced Camera for Surveys and wide-field imaging from Subaru Suprime-Cam. We spatially resolved integrated spectra out to ∼0.6 (NGC 1407) and ∼1.3 (NGC 1400) effective radii. The radial profiles of the kinematic parameters v _rot, σ, h ₃ and h ₄ are measured. The surface brightness profiles are fitted to different galaxy light models and the colour distributions analysed. The multiband images are modelled to derive isophotal shape parameters and residual galaxy images. The parameters from the surface brightness profile fitting are used to estimate the mass of the possible central supermassive black hole in NGC 1407. The galaxies are found to be rotationally supported and to have a flat core in the surface brightness profiles. Elliptical isophotes are observed at all radii and no fine structures are detected in the residual galaxy images. From our results, we can also discard a possible interaction between NGC 1400, NGC 1407 and the group intergalactic medium. We estimate a mass of  ∼1.03 × 10⁹ M_⊙  for the supermassive black hole in NGC 1407 galaxy.     

Prolonged Magmatic and Tectonic Development of the Caribbean Igneous Province Revealed by a Diving Submersible Survey

Using the diving submersible survey NAUTICA we investigated the central part of the Caribbean large igneous province (CLIP) to observe and sample internal portions of this proposed oceanic plateau. Most of the samples are gabbroic and doleritic rocks; basalts are scarce. Radiometric dating by ⁴⁰Ar/³⁹Ar incremental heating experiments indicate that the intrusive rocks are Campanian in age (81–75 Ma). In some places these intrusive rocks underlie older Santonian (85–83 Ma) extrusive basaltic rocks, suggesting that the Campanian rocks represent a sill injection and an underplating episode. Results of the diving program supplemented by information from ODP and DSDP drilling sites document a 20 m.y. period (94–75 Ma) of igneous activity in the submerged portion of the Caribbean large igneous province (CLIP). In the northern part of the Beata Ridge late Campanian and/or post Campanian uplift is documented by prominent Maastrichtian (71–65 Ma) erosion and the establishment of a Paleocene-middle Eocene (65–49 Ma) carbonate platform. During and after the uplift an extensional period is indicated by seismic images and the subsidence (3 km depth) of the carbonate platform. Paleocene ages (55–56 Ma) determined on some volcanic samples are attributed to localised decompression mantle melting that accompanied the extension. We document a prolonged period of magmatic and tectonic events that do not fit with the current models of short-lived plateau formation during mantle plume initiation but shares many similarities with the constructional histories of other oceanic large igneous provinces.     

The need for judgement in geotechnical reliability studies

ABSTRACT

A core principle of geotechnical engineering practice is the need to exercise judgement in evaluating soil and site conditions and in performing analyses. The requirement for considering judgement applies equally to performing deterministic or probabilistic analyses. In addition, for probabilistic analyses, choices must be made among the possible methods of analysis and the method of characterising variables. Consequently, geotechnical reliability studies inevitably involve significant uncertainties, and judgement is needed to perform reliability analyses and to evaluate the results. Two case histories, briefly described here, show that judgement and experience are essential prerequisites for meaningful assessment of geotechnical reliability.     

Atrazine Used as a Tracer of Induced Recharge

The city of Lincoln draws water from a well field along the banks of the Platte River in east-central Nebraska. We have been able to follow the infusion of atrazine into this well field under induced recharge. Samples of water from the river, several monitoring wells and a production well were analyzed by GC/MS and solid phase extraction and found to change in concentration over the range 0.1 and 5.0 ppb of atrazine through the spring, summer, and fall 1989. Increases in the concentration of atrazine relating to precipitation events in the Platte River Basin were observable in the well water samples and ultimately in Lincoln municipal tap water. Atrazine from the river was seen to move via induced recharge and into well field ground water and away from the river at an observable rate. The concentration of atrazine in the river is dependent upon time of year and precipitation in the river basin.     

Characterizing and classifying urban watersheds with compositional and structural attributes

Current land-use classifications used to assess urbanization effects on stream water quality date back to the 1980s when limited information was available to characterize watershed attributes that mediate non-point source pollution. With high resolution remote sensing and widely used GIS tools, there has been a vast increase in the availability and precision of geospatial data of built environments. In this study, we leverage geospatial data to expand the characterization of developed landscapes and create a typology that allows us to better understand the impact of complex developed landscapes across the rural to urban gradient. We assess the ability of the developed landscape typology to reveal patterns in stream water chemistry previously undetected by traditional land-cover based classification. We examine the distribution of land-cover, infrastructure, topography and geology across 3876 National Hydrography Dataset Plus catchments in the Piedmont region of North Carolina, USA. From this dataset, we generate metrics to evaluate the abundance, density and position of landscape features relative to streams, catchment outlets and topographic wetness metrics. While impervious surfaces are a key distinguishing feature of the urban landscape, sanitary infrastructure, population density and geology are better predictors of baseflow stream water chemistry. Unsupervised clustering was used to generate a distinct developed landscape typology based on the expanded, high-resolution landscape feature information. Using stream chemistry data from 37 developed headwater catchments, we compared the baseflow water chemistry grouped by traditional land-cover based classes of urbanization (rural, low, medium and high density) to our composition and structure-based classification (a nine-class typology). The typology based on 22 metrics of developed landscape composition and structure explained over 50% of the variation in NO₃⁻-N, TDN, DOC, Cl⁻, and Br⁻ concentration, while the ISC-based classification only significantly explained 23% of the variation in TDN. These results demonstrate the importance of infrastructure, population and geology in defining developed landscapes and improving discrete classes for water management.     

Comparison of surface and borehole locations of induced seismicity

Monitoring of induced microseismic events has become an important tool in hydraulic fracture diagnostics and understanding fractured reservoirs in general. We compare microseismic event and their uncertainties using data sets obtained with surface and downhole arrays of receivers. We first model the uncertainties to understand the effect of different acquisition geometries on location accuracy. For a vertical array of receivers in a single monitoring borehole, we find that the largest part of the final location uncertainty is related to estimation of the backazimuth. This is followed by uncertainty in the vertical position and radial distance from the receivers. For surface monitoring, the largest uncertainty lies in the vertical position due to the use of only a single phase (usually P‐wave) in the estimation of the event location. In surface monitoring results, lateral positions are estimated robustly and are not sensitive to the velocity model. In this case study, we compare event location solutions from two catalogues of microseismic events; one from a downhole array and the second from a surface array of 1C geophone. Our results show that origin time can be reliably used to find matching events between the downhole and surface catalogues. The locations of the corresponding events display a systematic shift consistent with a poorly calibrated velocity model for downhole dataset. For this case study, locations derived from surface monitoring have less scatter in both vertical and horizontal directions.     

Post-collapse volcanic history of calderas on a composite volcano: an example from Roccamonfina,southern Italy

Roccamonfina, part of the Roman Potassic Volcanic Province, is an example of a composite volcano with a complex history of caldera development. The main caldera truncates a cone constructed predominantly of this caldera may have been associated with one of the ignimbritic eruptions of the Brown Leucitic Tuff (BLT) around 385 000 yr BP. The Campagnola Tuff, the youngest ignimbrite of the BLT, however, drapes the caldera margin and must postdate at least the initial stages of collapse. During the subsequent history of the caldera there were several major explosive eruptions. The largest of these was that of the Galluccio Tuff at about 300 000 yr BP. It is likely that there was further collapse within the main caldera associated with these eruptions. It is of note that despite these subsequent major explosive eruptions later collapse occurred within the confines of the main caldera. Between eruptions caldera lakes developed producing numerous lacustrine beds within the caldera fill. Extensive phases of phreatomagmatic activity generated thick sequences of pyroclastic surge and fall deposits. Activity within the main caldera ended with the growth of a large complex of basaltic trachyandestite lava domes around 150 000 yr BP. Early in the history of Roccamonfina sector collapse on the northern flank of the volcano formed the northern caldera. One of the youngest major events on Roccamonfina occurred at the head of this northern caldera with explosive activity producing the Conca Ignimbrite and associated caldera. There is no evidence that there was any linkage in the plumbing systems that fed eruptions in the main and northern calderas.     

Placing geographies of public health

Following the move to a 'post–medical' geography, a large amount of research has come to focus on public health issues. This paper explores these current geographies of public health and argues for the development of a more critical perspective. In particular, it draws on commentary that has emerged out of debates that have taken place within a body of literature usually identified as the critical 'new' public health. The paper goes on to argue that such scholarship offers crucial insights for the production of a critical geography of public health.