LOFAR: first of a new generation of radio telescopes

Aperture plane detection of cosmic radio signals can confer several important advantages. The mechanical signal processing of conventional parabolic dish antennas can be replaced by signal processing purely in electronics and software, thereby placing aperture plane array instruments in a regime with decreasing future costs. Aperture arrays using all-sky element antennas also allow multiple, independent, full sensitivity telescopes to be formed in software. The Low Frequency Array (LOFAR) project aims to realize these advantages in a previously largely unexplored frequency domain, 10-240 MHz. Consisting of up to eight shared aperture telescopes operated independently over internet, it will explore the epoch of re-ionization, open the transient radio Universe to systematic study, record ultra-high energy cosmic particles and add a new dimension to solar and space physics research

The Evolution of galaxies in clusters. 5. A Study of populations since Z approximately equal to 0.5

The evolution of the colors of cluster galaxies since redshift of about 0.5 is studied using photometry of 33 clusters. In each cluster, those galaxies brighter than M(v) = -20 which are within the circular area containing the inner 30 percent of the total cluster population are selected. From the distribution of these galaxies in the color-magnitude plane, the fraction of galaxies whose rest-frame B-V colors are at least 0.2 mag bluer than the ridge line of the early-type galaxies at that magnitude is determined. It is found that low-redshift compact clusters form a very homogeneous group of objects with cores essentially devoid of blue galaxies. At redshifts greater than 0.1, compact clusters have significant numbers of blue galaxies, the fraction increasing with redshift. The colors of spiral galaxies in the cores of nearby clusters tend to be redder than those of spirals in the fiel

Absolute calibration of the LOPES antenna system

Radio emission in extensive air showers arises from an interaction with the geomagnetic field and is subject of theoretical studies. This radio emission has advantages for the detection of high energy cosmic rays compared to secondary particle or fluorescence measurement methods. Radio antennas like the LOPES30 antenna system are suited to investigate this emission process by detecting the radio pulses. The characteristic observable parameters like electric field strength and pulse length require a calibration which was done with a reference radio source resulting in an amplification factor representing the system behavior in the environment of the KASCADE-Grande experiment. Knowing the amplification factor and the gain of the LOPES antennas LOPES30 is calibrated absolutely for systematic analyses of the radio emission.Comment: 5 pages, Proceedings of International Workshop on Acoustic and Radio EeV Neutrino detection Activities: ARENA, May 17-19, 2005, DESY Zeuthe

Evolution since z = 0.5 of the Morphology-Density relation for Clusters of Galaxies

Using traditional morphological classifications of galaxies in 10 intermediate-redshift (z~0.5) clusters observed with WFPC-2 on the Hubble Space Telescope, we derive relations between morphology and local galaxy density similar to that found by Dressler for low-redshift clusters. Taken collectively, the `morphology-density' relationship, M-D, for these more distant, presumably younger clusters is qualitatively similar to that found for the local sample, but a detailed comparison shows two substantial differences: (1) For the clusters in our sample, the M-D relation is strong in centrally concentrated ``regular'' clusters, those with a strong correlation of radius and surface density, but nearly absent for clusters that are less concentrated and irregular, in contrast to the situation for low redshift clusters where a strong relation has been found for both. (2) In every cluster the fraction of elliptical galaxies is as large or larger than in low-redshift clusters, but the S0 fraction is 2-3 times smaller, with a proportional increase of the spiral fraction. Straightforward, though probably not unique, interpretations of these observations are (1) morphological segregation proceeds hierarchically, affecting richer, denser groups of galaxies earlier, and (2) the formation of elliptical galaxies predates the formation of rich clusters, and occurs instead in the loose-group phase or even earlier, but S0's are generated in large numbers only after cluster virialization.Comment: 35 pages, 19 figures, uses psfig. Accepted for publication in Ap

A Catalog of Morphological Types in 10 Distant Rich Clusters of Galaxies

We present catalogs of objects detected in deep images of 11 fields in 10 distant clusters obtained using WFPC-2 on board the Hubble Space Telescope. The clusters span the redshift range z=0.37-0.56 and are the subject of a detailed ground- and space-based study to investigate the evolution of galaxies as a function of environment and epoch. The data presented here include positions, photometry and basic morphological information on ~9000 objects in the fields of the 10 clusters. For a brighter subset of 1857 objects in these areas we provide more detailed morphological information.Comment: 24 pages, Latex (uses side.sty - included), 7 figures, accepted for publication in ApJS. Full tables, plates and images are to be distributed on AAS CD-ROM and are not included here. Catalogs now available at http://www.ociw.edu/~ir

Age estimation of Calliphora (Diptera: Calliphoridae) larvae using cuticular hydrocarbon analysis and Artificial Neural Networks

Cuticular hydrocarbons were extracted daily from the larvae of two closely related blowflies Calliphora vicina and Calliphora vomitoria (Diptera: Calliphoridae). The hydrocarbons were then analysed using Gas Chromatography–Mass Spectrometry (GC–MS), with the aim of observing changes within their chemical profiles in order to determine the larval age. The hydrocarbons were examined daily for each species from 1 day old larvae until pupariation. The results show significant chemical changes occurring from the younger larvae to the post-feeding larvae. With the aid of a multivariate statistical method (Principal Component Analysis and Artificial Neural Networks), samples were clustered and classified, allowing for the larval age to be established. Results from this study allowed larvae to be aged to the day with at worst, 87% accuracy, which suggests there is great potential for the use of cuticular hydrocarbons present on larvae to give an indication of their age and hence potentially a valuable tool for minimum PMI estimations

Detection and imaging of atmospheric radio flashes from cosmic ray air showers

The nature of ultrahigh-energy cosmic rays (UHECRs) at energies >10^20 eV remains a mystery. They are likely to be of extragalactic origin, but should be absorbed within ~50 Mpc through interactions with the cosmic microwave background. As there are no sufficient powerful accelerators within this distance from the Galaxy, explanations for UHECRs range from unusual astrophysical sources to exotic string physics. Also unclear is whether UHECRs consist of protons, heavy nuclei, neutrinos or gamma-rays. To resolve these questions, larger detectors with higher duty cycles and which combine multiple detection techniques are needed. Radio emission from UHECRs, on the other hand, is unaffected by attenuation, has a high duty cycle, gives calorimetric measurements and provides high directional accuracy. Here we report the detection of radio flashes from cosmic-ray air showers using low-cost digital radio receivers. We show that the radiation can be understood in terms of the geosynchrotron effect. Our results show that it should be possible to determine the nature and composition of UHECRs with combined radio and particle detectors, and to detect the ultrahigh-energy neutrinos expected from flavour mixing.Comment: Nature, May 19, 2005 issue (PDF, 14 pages), http://www.astro.ru.nl/lopes/?loc=publication

Progress in Air Shower Radio Measurements: Detection of Distant Events

Data taken during half a year of operation of 10 LOPES antennas (LOPES-10), triggered by EAS observed with KASCADE-Grande have been analysed. We report about the analysis of correlations of radio signals measured by LOPES-10 with extensive air shower events reconstructed by KASCADE-Grande, including shower cores at large distances. The efficiency of detecting radio signals induced by air showers up to distances of 700 m from the shower axis has been investigated. The results are discussed with special emphasis on the effects of the reconstruction accuracy for shower core and arrival direction on the coherence of the measured radio signal. In addition, the correlations of the radio pulse amplitude with the primary cosmic ray energy and with the lateral distance from the shower core are studied.Comment: Accepted for publication in Astroparticle Physic