Parametric Strong Gravitational Lensing Analysis of Abell 1689

(Abridged) We measure the mass distribution of galaxy cluster Abell 1689 within 0.3 Mpc/h_70 of the cluster centre using its strong lensing effect on 32 background galaxies. The multiple images are based on those of Broadhurst et al. 2005 with some modifications. The cluster profile is explored further out to ~2.5 Mpc/h_70 with weak lensing shear measurements from Broadhurst et al. 2005b. The masses of ~200 cluster galaxies are measured with Fundamental Plane in order to accurately model the small scale mass structure in the cluster. The galaxies are modelled as elliptical truncated isothermal spheres. The dark matter component of the cluster is described by either non-singular isothermal ellipsoids (NSIE) or elliptical versions of the universal dark matter profile (ENFW). We use two dark matter haloes to model the smooth DM in the cluster. The total mass profile is well described by either an NSIS profile with sigma=1514+-18 km/s and core radius of r_c=71+-5kpc/h_70, or an NFW profile with C=6.0+-0.5 and r_200=2.82+-0.11 Mpc/h_70. The errors are assumed to be due to the error in assigning masses to the individual galaxies in the galaxy component. The derived total mass is in good agreement with the mass profile of Broadhurst et al. 05. Using also weak lensing we can constrain the profile further out to r~2.5 Mpc/h_70. The best fit parameters are then sigma=1499+-15 km/s and r_c=66+-5 kpc/h_70 for the NSIS profile and C=7.6+-0.5 and r_200=2.55+-0.07 Mpc/h_70 for the NFW profile. Using the same image configuration as Broadhurst et al. 2005 we obtain a strong lensing model that is superior to that of Broadhurst et al. 2005 (rms of 2.7'' compared to 3.2'').Comment: 43 pages, 22 figures, submitted to the Monthly Notices of the Royal Astronomical Society after the first referee report. Full resolution paper available from http://www.usm.uni-muenchen.de/~halkola/A1689

Weak Lensing Mass Reconstruction: Flexion vs Shear

Weak gravitational lensing has proven to be a powerful tool to map directly the distribution of dark matter in the Universe. The technique, currently used, relies on the accurate measurement of the gravitational shear that corresponds to the first-order distortion of the background galaxy images. More recently, a new technique has been introduced that relies on the accurate measurement of the gravitational flexion that corresponds to the second-order distortion of the background galaxy images. This technique should probe structures on smaller scales than that of a shear analysis. The goal of this paper is to compare the ability of shear and flexion to reconstruct the dark matter distribution by taking into account the dispersion in shear and flexion measurements. Our results show that the flexion is less sensitive than shear for constructing the convergence maps on scales that are physically feasible for mapping, meaning that flexion alone not be used to do convergence map reconstruction, even on small scales.Comment: Submitted to Ap

Fiscal federalism and risk sharing in Germany: the role of size differences

We study the effect of size differences for an optimal risk sharing system of intergovernmental transfers in Germany. The German fiscal transfer system should account for the fact that an optimal insurance mechanism has the property that smaller states contribute a smaller share of their tax revenue to the redistribution mechanism. -- Wir betrachten die Rolle von Größenunterschieden von Gebietskörperschaften für einen optimalen Risikoausgleich im Rahmen eines föderalen Finanzausgleichs in Deutschland. Zunächst wird der Spielraum für einen möglichen Risikoausgleich durch interregionale Ausgleichszahlungen zwischen Gebietskörperschaften in Deutschland analysiert. Es zeigt sich, dass unsystematische Risiken insbesondere aus längerfristigen Entwicklungsunterschieden bestehen. Für das optimale Transfersystem sollte angesichts möglicher Anreizwirkungen solcher Systeme gelten, dass homogene Gebietskörperschaften einen um so größeren Anteil ihres Steueraufkommens in das interregionale Transfersystem einbringen sollten, je größer sie sind.Fiscal federalism,risk sharing,size asymmetry

On the Reverse Engineering of the Citadel Botnet

Citadel is an advanced information-stealing malware which targets financial information. This malware poses a real threat against the confidentiality and integrity of personal and business data. A joint operation was recently conducted by the FBI and the Microsoft Digital Crimes Unit in order to take down Citadel command-and-control servers. The operation caused some disruption in the botnet but has not stopped it completely. Due to the complex structure and advanced anti-reverse engineering techniques, the Citadel malware analysis process is both challenging and time-consuming. This allows cyber criminals to carry on with their attacks while the analysis is still in progress. In this paper, we present the results of the Citadel reverse engineering and provide additional insight into the functionality, inner workings, and open source components of the malware. In order to accelerate the reverse engineering process, we propose a clone-based analysis methodology. Citadel is an offspring of a previously analyzed malware called Zeus; thus, using the former as a reference, we can measure and quantify the similarities and differences of the new variant. Two types of code analysis techniques are provided in the methodology, namely assembly to source code matching and binary clone detection. The methodology can help reduce the number of functions requiring manual analysis. The analysis results prove that the approach is promising in Citadel malware analysis. Furthermore, the same approach is applicable to similar malware analysis scenarios.Comment: 10 pages, 17 figures. This is an updated / edited version of a paper appeared in FPS 201

Immittance Spectroscopy of Smart Components and Novel Devices

AC small-signal immittance spectroscopy is employed as a viable tool to demonstrate electrical characterization, performance improvement, and quality assurance issues of smart materials-based components and novel devices. The variation in the ac response, complemented via dc measurements within a range of tolerating temperature, delineates competing phenomena occurring in the microstructures of these engineering material systems. The results are presented in a generic manner with possible explanations on the mechanisms for two selected Debye-like (nearly ideal) and non-Debye (non-ideal) low-capacitance resistors. This spectroscopic approach allows systematic development of a representative equivalent circuit, considered to be the characteristic of the devices and components, for specific applications

Ionic conductivity and relaxation dynamics in plastic-crystals with nearly globular molecules

We have performed a dielectric investigation of the ionic charge transport and the relaxation dynamics in plastic-crystalline 1-cyano-adamantane (CNA) and in two mixtures of CNA with the related plastic crystals adamantane or 2-adamantanon. Ionic charge carriers were provided by adding 1% of Li salt. The molecules of these compounds have nearly globular shape and, thus, the so-called revolving-door mechanism assumed to promote ionic charge transport via molecular reorientations in other PC electrolytes, should not be active here. Indeed, a comparison of the dc resistivity and the reorientational alpha-relaxation times in the investigated PCs, reveals complete decoupling of both dynamics. Similar to other PCs, we find a significant mixing-induced enhancement of the ionic conductivity. Finally, these solid-state electrolytes reveal a second relaxation process, slower than the alpha-relaxation, which is related to ionic hopping. Due to the mentioned decoupling, it can be unequivocally detected and is not superimposed by the reorientational contributions as found for most other ionic conductors.Comment: 9 pages, 7 figure

Microlensing events from the 11-year observations of the Wendelstein Calar Alto Pixellensing Project

We present the results of the decade-long M31 observation from the Wendelstein Calar Alto Pixellensing Project (WeCAPP). WeCAPP has monitored M31 from 1997 till 2008 in both R- and I-filters, thus provides the longest baseline of all M31 microlensing surveys. The data are analyzed with the difference imaging analysis, which is most suitable to study variability in crowded stellar fields. We extracted light curves based on each pixel, and devised selection criteria that are optimized to identify microlensing events. This leads to 10 new events, and sums up to a total of 12 microlensing events from WeCAPP, for which we derive their timescales, flux excesses, and colors from their light curves. The color of the lensed stars fall between (R-I) = 0.56 to 1.36, with a median of 1.0 mag, in agreement with our expectation that the sources are most likely bright, red stars at post main-sequence stage. The event FWHM timescales range from 0.5 to 14 days, with a median of 3 days, in good agreement with predictions based on the model of Riffeser et al. (2006).Comment: 44 pages, 16 figures, 5 tables. ApJ accepte

Cosmic variance of the galaxy cluster weak lensing signal

Intrinsic variations of the projected density profiles of clusters of galaxies at fixed mass are a source of uncertainty for cluster weak lensing. We present a semi-analytical model to account for this effect, based on a combination of variations in halo concentration, ellipticity and orientation, and the presence of correlated haloes. We calibrate the parameters of our model at the 10 per cent level to match the empirical cosmic variance of cluster profiles at M_200m=10^14...10^15 h^-1 M_sol, z=0.25...0.5 in a cosmological simulation. We show that weak lensing measurements of clusters significantly underestimate mass uncertainties if intrinsic profile variations are ignored, and that our model can be used to provide correct mass likelihoods. Effects on the achievable accuracy of weak lensing cluster mass measurements are particularly strong for the most massive clusters and deep observations (with ~20 per cent uncertainty from cosmic variance alone at M_200m=10^15 h^-1 M_sol and z=0.25), but significant also under typical ground-based conditions. We show that neglecting intrinsic profile variations leads to biases in the mass-observable relation constrained with weak lensing, both for intrinsic scatter and overall scale (the latter at the 15 per cent level). These biases are in excess of the statistical errors of upcoming surveys and can be avoided if the cosmic variance of cluster profiles is accounted for.Comment: 14 pages, 6 figures; submitted to MNRA

A GPU Implementation for Two-Dimensional Shallow Water Modeling

In this paper, we present a GPU implementation of a two-dimensional shallow water model. Water simulations are useful for modeling floods, river/reservoir behavior, and dam break scenarios. Our GPU implementation shows vast performance improvements over the original Fortran implementation. By taking advantage of the GPU, researchers and engineers will be able to study water systems more efficiently and in greater detail.Comment: 9 pages, 1 figur