Reduction of the COSMOS Southern Sky galaxy survey data to the RC3 standard system

After having cross-identified a subsample of LEDA galaxies in the COSMOS database, we defined the best relations to convert COSMOS parameters (coordinates, position angle, diameter, axis ratio and apparent magnitude) into RC3 system used in the LEDA database. Tiny secondary effects can be tested: distance to plate cenetrs effect and air-mass effect. The converted COSMOS parameters are used to add missing parameters on LEDA galaxies. Key words: galaxies - catalogue - photometryComment: 5 pages, postcript including figures, to appear in MNRAS, reprint requests: [email protected]

Development of silicon carbide semiconductor devices for high temperature applications

The semiconducting properties of electronic grade silicon carbide crystals, such as wide energy bandgap, make it particularly attractive for high temperature applications. Applications for high temperature electronic devices include instrumentation for engines under development, engine control and condition monitoring systems, and power conditioning and control systems for space platforms and satellites. Discrete prototype SiC devices were fabricated and tested at elevated temperatures. Grown p-n junction diodes demonstrated very good rectification characteristics at 870 K. A depletion-mode metal-oxide-semiconductor field-effect transistor was also successfully fabricated and tested at 770 K. While optimization of SiC fabrication processes remain, it is believed that SiC is an enabling high temperature electronic technology

Planetesimal disk evolution driven by embryo-planetesimal gravitational scattering

The process of gravitational scattering of planetesimals by a massive protoplanetary embryo is explored theoretically. We propose a method to describe the evolution of the disk surface density, eccentricity, and inclination caused by the embryo-planetesimal interaction. It relies on the analytical treatment of the scattering in two extreme regimes of the planetesimal epicyclic velocities: shear-dominated (dynamically ``cold'') and dispersion-dominated (dynamically ``hot''). In the former, planetesimal scattering can be treated as a deterministic process. In the latter, scattering is mostly weak because of the large relative velocities of interacting bodies. This allows one to use the Fokker-Planck approximation and the two-body approximation to explore the disk evolution. We compare the results obtained by this method with the outcomes of the direct numerical integrations of planetesimal orbits and they agree quite well. In the intermediate velocity regime an approximate treatment of the disk evolution is proposed based on interpolation between the two extreme regimes. We also calculate the rate of embryo's mass growth in an inhomogeneous planetesimal disk and demonstrate that it is in agreement with both the simulations and earlier calculations. Finally we discuss the question of the direction of the embryo-planetesimal interaction in the dispersion-dominated regime and demonstrate that it is repulsive. This means that the embryo always forms a gap in the disk around it, which is in contrast with the results of other authors. The machinery developed here will be applied to realistic protoplanetary systems in future papers.Comment: 40 pages, 9 figures, submitted to A

Transient behavior of surface plasmon polaritons scattered at a subwavelength groove

We present a numerical study and analytical model of the optical near-field diffracted in the vicinity of subwavelength grooves milled in silver surfaces. The Green's tensor approach permits computation of the phase and amplitude dependence of the diffracted wave as a function of the groove geometry. It is shown that the field diffracted along the interface by the groove is equivalent to replacing the groove by an oscillating dipolar line source. An analytic expression is derived from the Green's function formalism, that reproduces well the asymptotic surface plasmon polariton (SPP) wave as well as the transient surface wave in the near-zone close to the groove. The agreement between this model and the full simulation is very good, showing that the transient "near-zone" regime does not depend on the precise shape of the groove. Finally, it is shown that a composite diffractive evanescent wave model that includes the asymptotic SPP can describe the wavelength evolution in this transient near-zone. Such a semi-analytical model may be useful for the design and optimization of more elaborate photonic circuits whose behavior in large part will be controlled by surface waves.Comment: 12 pages, 10 figure

Molecule mapping of HR8799b using OSIRIS on Keck: Strong detection of water and carbon monoxide, but no methane

Context. In 2015, Barman et al. (ApJ, 804, 61) presented detections of absorption from water, carbon monoxide, and methane in the atmosphere of the directly imaged exoplanet HR8799b using integral field spectroscopy (IFS) with OSIRIS on the Keck II telescope. We recently devised a new method to analyse IFU data, called molecule mapping, searching for high-frequency signatures of particular molecules in an IFU data cube. Aims. The aim of this paper is to use the molecule mapping technique to search for the previously detected spectral signatures in HR8799b using the same data, allowing a comparison of molecule mapping with previous methods. Methods. The medium-resolution H- and K-band pipeline-reduced archival data were retrieved from the Keck archive facility. Telluric and stellar lines were removed from each spectrum in the data cube, after which the residuals were cross-correlated with model spectra of carbon monoxide, water, and methane. Results. Both carbon monoxide and water are clearly detected at high signal-to-noise, however, methane is not retrieved. Conclusions. Molecule mapping works very well on the OSIRIS data of exoplanet HR8799b. However, it is not evident why methane is detected in the original analysis, but not with the molecule mapping technique. Possible causes could be the presence of telluric residuals, different spectral filtering techniques, or the use of different methane models. We do note that in the original analysis methane was only detected in the K-band, while the H-band methane signal could be expected to be comparably strong. More sensitive observations with the JWST will be capable of confirming or disproving the presence of methane in this planet at high confidence.Comment: 5 pages, 5 figures and 2 tables, accepted by A&