14480836
ISOCAM spectro-imaging of the H2 rotational lines in the supernova remnant IC 443
We report spectro-imaging observations of the bright western ridge of the supernova remnant IC 443 obtained with the ISOCAM circular variable filter (CVF) on board the In- frared Space Observatory (ISO) . This ridge corresponds to a location where the interaction between the blast wave of the supernova and ambient molecular gas is amongst the strongest. The CVF data show that the 5 to 14 m spectrum is domi- nated by the pure rotational lines of molecular hydrogen (v = 0-0, S(2) to S(8) transitions). At all positions along the ridge, the H2 rotational lines are very strong with typical line fluxes of 10 4 to10 3 erg s 1 cm 2 sr 1 . We compare the data to a new time-dependent shock model; the rotational line fluxes in IC 443 are reproduced within factors of 2 for evolutionary times between 1,000 and 2,000 years with a shock velocity of 30kms 1 and a pre-shock density of 10 4 cm 3 .
17282332
Disks around the Young Stars TW Hydrae and HD 100546 Imaged at 3.4 Millimeters with the Australia Telescope Compact Array
We present observations of the young stars TW Hya and HD 100546 made with the Australia Telescope Compact Array at 89 GHz with ~2'' resolution and ~3 mJy continuum sensitivity. Compact thermal dust continuum emission is detected from disks surrounding both stars. HD 100546 also shows hints of extended emission, presumably a residual protostellar envelope, which is also visible in scattered light at optical wavelengths. For TW Hya, HCO+ J = 1-0 line emission from the circumstellar disk is detected and spatially resolved. The observed size and intensity are in good agreement with model calculations based on an irradiated disk with substantial depletions derived previously from single-dish observations of higher J HCO+ transitions.
118866213
ISO-SWS observations of pure rotational water absorption lines toward Orion-IRc2
First detections of thermal water vapor absorption lines have been made toward Orion IRc2 using the Short Wavelength Spectrometer (SWS) on board the Infrared Space Observatory (ISO). Grating spectra covering wavelengths 25-45 micron yield 19 pure rotational lines, originating from energy levels 200-750 K above ground. Fabry-Perot spectra of 5 transitions resolve the line profiles and reveal the water gas kinematics. The fact that all lines are seen in absorption is in striking contrast with data from the ISO Long Wavelength Spectrometer (LWS), where the water lines appear in emission. At least one line displays a P-Cygni type profile, which suggests that the water is located in an expanding shell centered on or near IRc2. The expansion velocity is 18 km per second, in agreement with the value inferred from water maser observations by Genzel et al. (1981). Because the continuum is intense and likely formed in or near the water-containing gas, the excitation of the observed transitions is dominated by radiative processes. A simple, generalised curve-of-growth method is presented and used to analyze the data. A mean excitation temperature of 72 K and a total water column density of 1.5e18 molecules per cm squared are inferred, each with an estimated maximum uncertainty of 20%. Combined with the molecular hydrogen column density derived from ISO observations of the pure rotational lines, and an assumed temperature of 200-350 K, the inferred water abundance is 2e-4 to 5e-4 in the warm shocked gas. This abundance is similar to that found recently by Harwit et al. (1998) toward Orion using data from the LWS, but higher than that found for most other shocked regions by, for example, Liseau et al. (1996).
117044525
Gas-phase H2O and CO2 toward massive protostars
We present a study of gas-phase H2O and CO2 toward a sample of 14 massive protostars with the Short Wavelength Spectrometer (SWS) on board the Infrared Space Observatory (ISO). Modeling of the H2O spectra using a homogeneous model with a constant excitation temperature T_ex shows that the H2O abundances increase with temperature, up to a few times 10^-5 with respect to H2 for the hottest sources (T_ex ~500 K). This is still a factor of 10 lower than the H2O ice abundances observed toward cold sources in which evaporation is not significant (Keane et al. 2001). Gas-phase CO2 is not abundant in our sources. The abundances are nearly constant for T_ex>~100 K at a value of a few times 10^-7, much lower than the solid-state abundances of ~1--3 times 10^-6 (Gerakines et al. 1999). For both H2O and CO2 the gas/solid ratio increases with temperature, but the increase is much stronger for H2O than for CO2, suggesting a different type of chemistry. In addition to the homogeneous models, a power law model has been developed for one of our sources, based on the physical structure of this region as determined from submillimeter data by van der Tak et al. (1999). The resulting H2O model spectrum gives a good fit to the data.
54217863
NOVEL TECHNIQUES USING FEM FOR MATERIAL PRODUCTION AND PROCESSING
The objectives of this European project are to use high frequency microwave technology to develop focused energy sources for industrial applications. The microwaves, generated in the 10GHz to 20GHz frequency range by using a table top FEM has been used to investigate novel solutions for material processing and material production, including microwave heating of substrates, microwave chemistry for increasing the speed of thermal reactions, microwave plasma chemistry for aiding gaseous reactions in the reduction of combustion pollutants and the production of UV/ozone for germicidal activities. In this paper we report unique results and analysis in using tuneable FEM system compared with the conventional magnetron 2.45 GHz system.
16842883
A Comparison of Simple Mass Estimators for Galaxy Clusters
High-resolution N-body simulations are used to investigate systematic trends in the mass profiles and total masses of clusters as derived from three simple estimators: (1) the weak gravitational lensing shear field, under the assumption of an isothermal cluster potential; (2) the dynamical mass obtained from the measured velocity dispersion, under the assumption of an isothermal cluster potential; and (3) the classical virial estimator. The clusters used for the analysis were obtained from simulations of a standard cold dark matter universe at z = 0.5 and consist of order ? 105 particles of mass mp 1010 M?. The clusters are not smooth and spherically symmetric but, rather, the mass distribution is triaxial, and significant substructure exists within the clusters. Not surprisingly, the level of agreement between the cluster mass profiles obtained from the various estimators and the actual mass profiles is found to be scale-dependent. We define the total cluster mass to be the mass contained within a three-dimensional radius r200 of the cluster centers, where r200 is the radius inside which the mean interior overdensity is equal to 200. Under this definition the classical virial estimator yields a good measurement of the total cluster mass, although it is systematically underestimated by ~10%. This result suggests that, at least in the limit of ideal data, the virial estimator is quite robust to deviations from pure spherical symmetry and the presence of substructure within a cluster. The dynamical mass estimate based upon a measurement of the cluster velocity dispersion and an assumption of an isothermal potential yields a poor measurement of the total cluster mass, underestimating it by ~40% for the case in which ?v is computed from an average over the entire cluster. The weak lensing estimate yields a very good measurement of the total cluster mass, provided that the mean shear used to determine the equivalent cluster velocity dispersion is computed from an average of the lensing signal over the entire cluster (i.e., the mean shear is computed interior to a projected cluster radius of R200).
110675795
Architecture of the MEGA detector trigger
Abstract The trigger for the MEGA detector system is based on signals from single, high-energy photons interacting in one of the three MEGA pair spectrometers. The trigger is divided into a fast and a slow stage. The first stage produces a fast output if a specific pattern of detector hits is observed in the scintillators and high-speed wire chambers of a pair spectrometer. The second, slow-stage interrogates drift chamber hit patterns and provides a veto when the pattern fails a minimal requirement for reconstruction of the hits into a pair of circular orbits. The trigger interacts with the photon detector electronics by gating limited sections of the detector during the read-out of an event. This paper describes the two stage trigger system, the photon detector electronics, and the implementation of the trigger outputs to strobe the data acquisition system. The performance of the trigger is compared to Monte Carlo simulations of the photon detector response.
15605593
Multiple weak deflections and the detection of flattened halos with galaxy-galaxy lensing
We investigate the occurrence of multiple weak deflections in deep data sets which are used to detect galaxy-galaxy lensing. Using the galaxies in the HDF (North) for which both redshifts and rest-frame blue luminosities are known, we show that the probability for a given source galaxy to be lensed by two or more foreground galaxies exceeds 50% for z_s > 1, and for which the separate, individual deflections yield gamma > 0.005. Neglecting multiple deflections when obtaining best-fitting halo parameters for the lens galaxies can lead to an overestimate by a factor of order 2 for the halo mass interior to a radius of 100 kpc/h. We also show that multiple weak deflections create systematic effects which may hinder observational efforts to use weak lensing to constrain the projected shapes of the halos of field galaxies. For a data set in which the galaxies have magnitudes in the rage 19 < I < 23, multiple deflections result in strong correlations between the post-lensing image shapes of most foreground-background pairs of galaxies. Imposing a simple redshift cut during the data anaysis is sufficient to reduce the correlation between the final images of lenses and sources to the point that the expected anisotropy in the weak lensing signal can be detected via a straightforward average. We conclude that previous theoretical calculations of weak lensing due to flattened halos have considerably underestimated the sizes of the observational data sets which would be required to detect this effect. [Abridged]
94022512
SOLVING DYNAMIC EQUATIONS FOR THE COLLECTION AND EVAPORATION OF AN AEROSOL
We investigate the coalescence of drops undergoing random Brownian motion and evaporation. The evolution of the drop size spectrum is determined by solving a partial integro-differential equation with a kernel that describes the pairwise coalescence of drops. Numerical results for fuel injection with n-octane suggest that the size distribution of drops is determined by two competing processes, namely coalescence and evaporation. 
 
 
 
Nous etudions ici la coalescence de gouttes dans des conditions de deplacement brownien aleatoire et d'evaporation. L'evolution du spectre de la taille des gouttes est determinee par la resolution d'une equation integro-differentielle partielle avec un noyau qui decrit la coalescence par paire des gouttes. Les resultats numeriques pour l'injection du fuel avec du n-octane suggkrent que la distribution de taille des gouttes est determinee par deux processus se faisant concurrence, a savoir la coalescence et l'evaporation.