No evidence for a `redshift cut-off' for the most powerful classical double radio sources

We use three samples (3CRR, 6CE and 6C*) to investigate the radio luminosity function (RLF) for the `most powerful' low-frequency selected radio sources. We find that the data are well fitted by a model with a constant co-moving space density at high redshift as well as by one with a declining co-moving space density above some particular redshift. This behaviour is very similar to that inferred for steep-spectrum radio quasars by Willott et al (1998) in line with the expectations of Unified Schemes. We conclude that there is as yet no evidence for a `redshift cut-off' in the co-moving space densities of powerful classical double radio sources, and rule out a cut-off at z < 2.5.Comment: To appear in `The Hy-redshift universe: Galaxy formation and evolution at high redshift' eds. A.J. Bunker and W.J.M. van Breuge

The mass of radio galaxies from low to high redshift

Using a new radio sample, 6C* designed to find radio galaxies at z > 4 along with the complete 3CRR and 6CE sample we extend the radio galaxy K-z relation to z~4.5. The 6C* K-z data significantly improve delineation of the K-z relation for radio galaxies at high redshift (z >2). In a spatially flat universe with a cosmological constant (Omega_M=0.3 and Omega_Lambda=0.7), the most luminous radio sources appear to be associated with galaxies with a luminosity distribution with a high mean (~5L*), and a low dispersion (~0.5 mag) which formed their stars at epochs corresponding to z >~ 2.5.Comment: 6 pages, 3 figures. To appear in ESO conference "The mass of galaxies from low to high redshift", Venice Oct 24-26, 200

The discovery of a typical radio galaxy at z = 4.88

‘The definitive version is available at www3.interscience.wiley.com '. Copyright Royal Astronomical Society. DOI: 10.1111/j.1745-3933.2009.00715.xIn this Letter, we report the discovery of a z= 4.88 radio galaxy discovered with a new technique which does not rely on pre-selection of a sample based on radio properties such as steep-spectral index or small angular size. This radio galaxy was discovered in the Elais-N2 field and has a spectral index of α= 0.75 , i.e. not ultra-steep spectrum. It also has a luminosity consistent with being drawn from the break of the radio luminosity function and can therefore be considered as a typical radio galaxy. Using the Spitzer Wide-Area Infrared Extragalactic Survey (SWIRE) data over this field, we find that the host galaxy is consistent with being similarly massive to the lower redshift powerful radio galaxies (∼1–3L★) . However, we note that at z= 4.88, the Hα line is redshifted into the IRAC 3.6 μm filter, and some of the flux in this band may be due to this fact rather than the stellar continuum emission. The discovery of such a distant radio source from our initial spectroscopic observations demonstrates the promise of our survey for finding the most distant radio sources.Peer reviewe

Effects of carbon dioxide on the searching behaviour of the root-feeding clover weevil <i>Sitona lepidus</i> (Coleoptera: Curculionidae)

The respiratory emission of CO2 from roots is frequently proposed as an attractant that allows soil-dwelling insects to locate host plant roots, but this role has recently become less certain. CO2 is emitted from many sources other than roots, so does not necessarily indicate the presence of host plants, and because of the high density of roots in the upper soil layers, spatial gradients may not always be perceptible by soil-dwelling insects. The role of CO2 in host location was investigated using the clover root weevil Sitona lepidus Gyllenhall and its host plant white clover (Trifolium repens L.) as a model system. Rhizochamber experiments showed that CO2 concentrations were approximately 1000 ppm around the roots of white clover, but significantly decreased with increasing distance from roots. In behavioural experiments, no evidence was found for any attraction by S. lepidus larvae to point emissions of CO2, regardless of emission rates. Fewer than 15% of larvae were attracted to point emissions of CO2, compared with a control response of 17%. However, fractal analysis of movement paths in constant CO2 concentrations demonstrated that searching by S. lepidus larvae significantly intensified when they experienced CO2 concentrations similar to those found around the roots of white clover (i.e. 1000 ppm). It is suggested that respiratory emissions of CO2 may act as a ‘search trigger’ for S. lepidus, whereby it induces larvae to search a smaller area more intensively, in order to detect location cues that are more specific to their host plant.<br/

Study of Metal Magnetic Memory (MMM) Technique Using Permanently Installed Magnetic Sensor Arrays

The Metal magnetic memory (MMM) technique is marketed as a non-destructive testing method to evaluate stress concentration for ferromagnetic materials by measuring variations of the self-magnetic leakage field (SMLF) distribution on the specimen surface. This method has been implemented as a periodic screening inspection tool by several companies, and has been reported to be capable of detecting stress concentration in some instances. However, recent literature has suggested that the performance can be unreliable, with many false-calls; however, the reason for the false calls has not been satisfactorily investigated. In this paper, the normal and tangential components of the stress induced SMLF on the surface of specimens made from L80 steel, which is commonly used for pipes in the petrochemical industry, were measured by two permanently installed magnetic sensor arrays under the earth’s magnetic field. The results show that the SMLF changes are very small (about 10 ~ 30 A/m) in all cases for the material tested and occur mainly in first elastic load cycle. A Finite Element (FE) model has been used to predict the spatial distribution of the magnetic field due to localized MMM. The FE studies show that the defect size and the applied background magnetic field will influence the SMLF signal; however, the signal due to MMM could be swamped by any ferromagnetic material near to the magnetic sensors. The simulation and experimental results demonstrate the high probability of false calls with the MMM technique even if there were a significant MMM effect in the material used

Seasonal variations of gravity wave activity in the lower stratosphere over an Antarctic Peninsula station

An 8 year series of 965 high-resolution radiosonde soundings over Rothera (67 degrees S, 68 degrees W) on the Antarctic Peninsula are used to study gravity wave characteristics in the lower stratosphere. The gravity wave energy is shown to have a seasonal variation with peaks at the equinoxes; the largest peak is around the spring equinox. During the winter months and extending into the spring, there is both an enhancement in the downward propagating wave activity and a reduction in the amount of critical-level filtering of upward propagating mountain waves. The horizontal propagation directions of the gravity waves were determined using hodographs. It was found that there is a predisposition toward northward and westward propagating waves above Rothera. This is in agreement with previous observations of gravity wave momentum flux in the wintertime mesosphere over Rothera. These results are consistent with a scenario whereby the stratospheric gravity wavefield above Rothera is determined by a combination of wind flow over topography-generating waves from below, and sources such as the edge of the polar stratospheric vortex-generating waves from above, especially during winter and spring

Evidence of a link between the evolution of clusters and their AGN fraction

We discuss the optical properties, X-ray detections and active galactic nucleus (AGN) populations of four clusters at z ~ 1 in the Subaru–XMM Deep Field (SXDF). The velocity distribution and plausible extended X-ray detections are examined, as well as the number of X-ray point sources and radio sources associated with the clusters. We find that the two clusters that appear virialized and have an extended X-ray detection contain few, if any, AGN, whereas the two pre-virialized clusters have a large AGN population. This constitutes evidence that the AGN fraction in clusters is linked to the clusters' evolutionary stage. The number of X-ray AGN in the pre-virialized clusters is consistent with an overdensity of a factor of ~200; the radio AGN appear to be clustered with a factor of 3 to 6 higher. The median K-band luminosities of L_K= 1.7 ± 0.7 L* for the X-ray sources and L_K= 2.3 ± 0.1 L* for the radio sources support the theory that these AGN are triggered by galaxy interaction and merging events in sub-groups with low internal velocity distributions, which make up the cluster environment in a pre-virialization evolutionary stage

Augmentation of Cognition and Perception Through Advanced Synthetic Vision Technology

Synthetic Vision System technology augments reality and creates a virtual visual meteorological condition that extends a pilot's cognitive and perceptual capabilities during flight operations when outside visibility is restricted. The paper describes the NASA Synthetic Vision System for commercial aviation with an emphasis on how the technology achieves Augmented Cognition objectives