The Resolved Outer Population of NGC6822 with WFPC2

We present F336W (U), F439W (B), F555W (V), and F675W (R) Wide Field Planetary Camera 2 (WFPC2) photometry of two outer regions of the Local Group dwarf irregular galaxy NGC6822. The NE region is ~13 arcmin from the galaxy centre, while the W region lies 10 arcmin out, and within the wispy low surface brightness outer regions of the galaxy. The fields are not crowded and contain few NGC 6822 stars. We discuss errors and uncertainties and find that the W region contains a main sequence that extends to stars of about 2 solar masses, with an age of about 200 Myr. The NE region has no main sequence or stars younger than 1 Gyr, but does contain some luminous red stars that are not matched in the W field. These stars are not clumped in the field. The results suggest that the W region may be a trace of a tidal event that triggered the current star-formation in this isolated galaxy.Comment: 12 pages including 2 tables, plus 4 figures (#1 omitted) To appear in PAS

Stimulation of Root Growth on Cuttings from Hardwood Forest Trees

Certain trees and shrubs may more easily be propagated from cuttings than from seed. Others may be regenerated by root or stem layering. It is well known that new trees of willow, poplar or sycamore may readily be produced by cuttings separated from the parent tree and planted in soil or sand under favorable conditions of temperature and moisture

CONTRIBUTIONS OF THE BENGUELA ECOLOGY PROGRAMME TO PELAGIC FISHERIES MANAGEMENT IN SOUTH AFRICA

In 1982, the Benguela Ecology Programme (BEP) created a formal, multi-institutional research partnership in South Africa. During the next two decades, the BEP directed many aspects of pelagic ecosystem research in the southern Benguela upwelling region, aiming to improve fisheries management, particularly that of anchovy Engraulis encrasicolus. Although much reduced in scale, the BEP is now in its fifth phase. Its early critics believed that much of the money invested in its ecosystem-type research had not benefited fisheries management, whereas its supporters maintain that many aspects of current pelagic fisheries management are founded on the BEP legacy. Ecosystem research underpinned the design of hydroacoustic surveys, and resulted in the development of expert system models aimed at predicting recruitment strength of anchovy. Current efforts to develop an ecosystem approach to management of the pelagic fishery in South Africa draw on the knowledge and understanding generated by more than 20 years of ecosystem research. However, despite this strong foundation, there is still uncertainty about the causes of interannual variability in pelagic fish recruitment. It is suggested that this time span is too short, and ecosystem monitoring and research should persist for decades to reap their full rewards. The BEP enabled productive partnerships to be established between academic and State researchers and fisheries managers, and improved linkages and communication to the fishing industry. Afr. J. mar. Sci. 26: 37–5

Near-infrared adaptive optics imaging of high redshift quasars

The properties of high redshift quasar host galaxies are studied, in order to investigate the connection between galaxy evolution, nuclear activity, and the formation of supermassive black holes. We combine new near-infrared observations of three high redshift quasars (2 < z < 3), obtained at the ESO Very Large Telescope equipped with adaptive optics, with selected data from the literature. For the three new objects we were able to detect and characterize the properties of the host galaxy, found to be consistent with those of massive elliptical galaxies of M(R) ~ -24.7 for the one radio loud quasar, and M(R) ~ -23.8 for the two radio quiet quasars. When combined with existing data at lower redshift, these new observations depict a scenario where the host galaxies of radio loud quasars are seen to follow the expected trend of luminous (~5L*) elliptical galaxies undergoing passive evolution. This trend is remarkably similar to that followed by radio galaxies at z > 1.5. Radio quiet quasars hosts also follow a similar trend but at a lower average luminosity (~0.5 mag dimmer). The data indicate that quasar host galaxies are already fully formed at epochs as early as ~2 Gyr after the Big Bang and then passively fade in luminosity to the present epoch.Comment: Accepted for publication in ApJ, 24 pages, 10 figure

Validation of Methods to Predict Vibration of a Panel in the Near Field of a Hot Supersonic Rocket Plume

This paper describes the measurement and analysis of surface fluctuating pressure level (FPL) data and vibration data from a plume impingement aero-acoustic and vibration (PIAAV) test to validate NASA s physics-based modeling methods for prediction of panel vibration in the near field of a hot supersonic rocket plume. For this test - reported more fully in a companion paper by Osterholt & Knox at 26th Aerospace Testing Seminar, 2011 - the flexible panel was located 2.4 nozzle diameters from the plume centerline and 4.3 nozzle diameters downstream from the nozzle exit. The FPL loading is analyzed in terms of its auto spectrum, its cross spectrum, its spatial correlation parameters and its statistical properties. The panel vibration data is used to estimate the in-situ damping under plume FPL loading conditions and to validate both finite element analysis (FEA) and statistical energy analysis (SEA) methods for prediction of panel response. An assessment is also made of the effects of non-linearity in the panel elasticity

STIS Echelle Observations of the Seyfert Galaxy NGC 4151: Physical Conditions in the Ultraviolet Absorbers

We have examined the physical conditions in intrinsic UV-absorbing gas in the Seyfert galaxy NGC 4151, using echelle spectra obtained with the Space Telescope Imaging Spectrograph (STIS). We confirm the presence of the kinematic components detected in earlier GHRS observations as well as a new broad absorption feature at a radial velocity of -1680 km/s. The UV continuum of NGC 4151 decreased by a factor of 4 over the previous two years, and we argue the changes in the column density of the low ionization absorption lines associated with the broad component at -490 km/s reflect the decrease in the ionizing flux. Most of the strong absorption lines (e.g., N V, C IV, Si IV) from this component are saturated, but show substantial residual flux in their cores, indicating that the absorber does not fully cover the source of emission. Our interpretation is that the unocculted light is due to scattering by free electrons from an extended region, which reflects continuum, emission lines, and absorption lines. We have been able to constrain the densities for the kinematic components based on absorption lines from metastable states of C III and Fe II, and/or the ratios of ground and fine structure lines of O I,C II, and Si II. We have generated a set of photoionization models which match the ionic column densities for each component during the present low flux state and those seen in previous high flux states with the GHRS and STIS, confirming that the absorbers are photoionized and respond to the changes in the continuum flux. We have been able to map the relative radial positions of the absorbers, and find that the gas decreases in density with distance. None of the UV absorbers is of sufficiently large column density or high enough ionization state to account for the X-ray absorption.Comment: 46 pages (Latex), 14 figures (postscript), plus a landscape table (Latex), to appear in the Astrophysical Journa

Magnetic properties of single-crystalline CeCuGa3

The magnetic behavior of single-crystalline CeCuGa3 has been investigated. The compound forms in a tetragonal BaAl4-type structure consisting of rare-earth planes separated by Cu-Ga layers. If the Cu-Ga site disorder is reduced, CeCuGa3 adopts the related, likewise tetragonal BaNiSn3-type structure, in which the Ce ion are surrounded by different Cu and Ga layers and the inversion symmetry is lost. In the literature conflicting reports about the magnetic order of CeCuGa3 have been published. Single crystals with the centrosymmetric structure variant exhibit ferromagnetic order below approx. 4 K with a strong planar anisotropy. The magnetic behavior above the transition temperature can be well understood by the crystal-field splitting of the 4f Hund's rule ground-state multiplet of the Ce ions