Exchange-rate effects on China's trade: an interim report

The rising current account deficit in the USA has attracted considerable attention in recent years. We use the "business cycle accounting" methodology to identify the principal distortions that have affected the external accounts of the US. In particular, we measure distortions in the optimality conditions of a simple two-country general equilibrium model using data from the US and the other G7 countries. We then feed these measured distortions into the model individually and use the simulated counterfactual paths of the current account to determine the contribution of each of these "wedges" to the overall external imbalance of the USA. We find that no single wedge in isolation can account closely for the observed current account. However, a combination of productivity differences and deviations from risk-sharing between the US and the rest of the G7 does the best job in accounting for most of the measured movement of the US current account.Foreign exchange rates - China ; Trade ; Econometric models

The effect of ram pressure on the star formation, mass distribution and morphology of galaxies

We investigate the dependence of star formation and the distribution of the components of galaxies on the strength of ram pressure. Several mock observations in X-ray, H$\alpha$ and HI wavelength for different ram-pressure scenarios are presented. By applying a combined N-body/hydrodynamic description (GADGET-2) with radiative cooling and a recipe for star formation and stellar feedback 12 different ram-pressure stripping scenarios for disc galaxies were calculated. Special emphasis was put on the gas within the disc and in the surroundings. All gas particles within the computational domain having the same mass resolution. The relative velocity was varied from 100 km/s to 1000 km/s in different surrounding gas densities in the range from $1\times10^{-28}$ to $5\times10^{-27}$ g/cm$^3$. The temperature of the surrounding gas was initially $1\times10^{7}$ K. The star formation of a galaxy is enhanced by more than a magnitude in the simulation with a high ram-pressure ($5\times10^{-11}$ dyn/cm$^2$) in comparison to the same system evolving in isolation. The enhancement of the star formation depends more on the surrounding gas density than on the relative velocity. Up to 95% of all newly formed stars can be found in the wake of the galaxy out to distances of more than 350 kpc behind the stellar disc. Continuously stars fall back to the old stellar disc, building up a bulge-like structure. Young stars can be found throughout the stripped wake with surface densities locally comparable to values in the inner stellar disc. Ram-pressure stripping can shift the location of star formation from the disc into the wake on very short timescales. (Abridged)Comment: 19 pages, 25 figures, A&A accepted, high resolution version can be found at http://astro.uibk.ac.at/~wolfgang/kapferer_rps_galaxies.pd

ATCA observations of the galaxy cluster Abell 3921 - I. Radio emission from the central merging sub-clusters

We present the analysis of our 13 and 22 cm ATCA observations of the central region of the merging galaxy cluster A3921 (z=0.094). We investigated the effects of the major merger between two sub-clusters on the star formation (SF) and radio emission properties of the confirmed cluster members. The origin of SF and the nature of radio emission in cluster galaxies was investigated by comparing their radio, optical and X-ray properties. We also compared the radio source counts and the percentage of detected radio galaxies with literature data. We detected 17 radio sources above the flux density limit of 0.25 mJy/beam in the central field of A3921, among which 7 are cluster members. 9 galaxies with star-forming optical spectra were observed in the collision region of the merging sub-clusters. They were not detected at radio wavelengths, giving upper limits for their star formation rate significantly lower than those typically found in late-type, field galaxies. Most of these star-forming objects are therefore really located in the high density part of the cluster, and they are not infalling field objects seen in projection at the cluster centre. Their SF episode is probably related to the cluster collision that we observe in its very central phase. None of the galaxies with post-starburst optical spectra was detected down our 2$\sigma$ flux density limit, confirming that they are post-starburst and not dusty star-forming objects. We finally detected a narrow-angle tail (NAT) source associated with the second brightest cluster galaxy (BG2), whose diffuse component is a partly detached pair of tails from an earlier period of activity of the BG2 galaxy.Comment: 17 pages, 9 figures, accepted for publication in A&A, date of acceptance 29/06/2006. A version of the paper with higher resolution images can be downloaded at: http://astro.uibk.ac.at/~c.ferrari/ATCA_Paper/A3921_ATCA.pd

Internal kinematics of isolated modelled disk galaxies

We present a systematic investigation of rotation curves (RCs) of fully hydrodynamically simulated galaxies, including cooling, star formation with associated feedback and galactic winds. Applying two commonly used fitting formulae to characterize the RCs, we investigate systematic effects on the shape of RCs both by observational constraints and internal properties of the galaxies. We mainly focus on effects that occur in measurements of intermediate and high redshift galaxies. We find that RC parameters are affected by the observational setup, like slit misalignment or the spatial resolution and also depend on the evolution of a galaxy. Therefore, a direct comparison of quantities derived from measured RCs with predictions of semi-analytic models is difficult. The virial velocity V_c, which is usually calculated and used by semi-analytic models can differ significantly from fit parameters like V_max or V_opt inferred from RCs. We find that V_c is usually lower than typical characteristic velocities derived from RCs. V_max alone is in general not a robust estimator for the virial mass.Comment: 9 pages, 15 figures, accepted for publication in A&

Geoscience of Climate and Energy 12. Water Quality Issues in the Oil Sands Region of the Lower Athabasca River, Alberta

I summarize the controversies about industrial pollutants in freshwaters near the oil sands industrial area of Alberta, the inadequacies in environmental monitoring that have led to widespread misconceptions, and recent attempts to correct the problems.  Adequate data are available to show that mercury, other trace metals, and polycyclic aromatic compounds are being added by industry to the Athabasca river system and its watershed, although the relative contributions of industrial development and natural sources remain in question.  Recent improvements in water monitoring by Environment Canada show promise of resolving the controversies, although independent governance for Canada’s and Alberta’s water monitoring programs in the lower Athabasca River will be necessary to rebuild public confidence in the data and their interpretation by government and industry.  I document one success story in the Athabasca River: the elimination of dioxins from pulp mills in the mid-1990s has caused a consumption advisory for fish in the river to be repealed.SOMMAIREJe présente ci-dessous un résumé des controverses concernant les polluants industriels dans les eaux douces à proximité de la zone industrielle des sables bitumineux de l'Alberta, des lacunes dans la surveillance des milieux de vie à l’origine d’idées fausses répandues, et de récentes tentatives visant à corriger les problèmes.  Des données adéquates démontrent que l’industrie ajoute du mercure et d'autres métaux traces ainsi que des composés aromatiques polycycliques dans le système fluvial de la rivière Athabasca et dans son bassin versant, bien que les contributions relatives provenant de ces activités industrielles et de sources naturelles demeurent toujours en litige.  De récentes améliorations apportées au contrôle des eaux par Environnement Canada permettent d’espérer une résolution des controverses, mais l’application d’une gouvernance indépendante des programmes de contrôle de l'eau de l'Alberta du Canada dans la partie inférieure du fleuve Athabasca sera nécessaire pour rétablir la confiance de la population à l’égard des données présentées et de leur interprétation par le gouvernement et l'industrie.  Je décrie l’histoire d’une intervention réussie dans la rivière Athabasca, soit l'élimination de dioxines provenant des usines de pâte du milieu des années 1990 et qui a abouti à l’abrogation d’un avis de limitation de la consommation de poisson dans la rivière.DOI: http://dx.doi.org/10.12789/geocanj.2013.40.01

Internal kinematics of modelled interacting disc galaxies

We present an investigation of galaxy-galaxy interactions and their effects on the velocity fields of disc galaxies in combined N-body/hydrodynamic simulations, which include cooling, star formation with feedback, and galactic winds. Rotation curves (RCs) of the gas are extracted from these simulations in a way that follows the procedure applied to observations of distant, small, and faint galaxies as closely as possible. We show that galaxy-galaxy mergers and fly-bys disturb the velocity fields significantly and hence the RCs of the interacting galaxies, leading to asymmetries and distortions in the RCs. Typical features of disturbed kinematics are significantly rising or falling profiles in the direction of the companion galaxy and pronounced bumps in the RCs. In addition, tidal tails can leave strong imprints on the rotation curve. All these features are observable for intermediate redshift galaxies, on which we focus our investigations. We use a quantitative measure for the asymmetry of rotation curves to show that the appearance of these distortions strongly depends on the viewing angle. We also find in this way that the velocity fields settle back into relatively undisturbed equilibrium states after unequal mass mergers and fly-bys. About 1 Gyr after the first encounter, the RCs show no severe distortions anymore. These results are consistent with previous theoretical and observational studies. As an illustration of our results, we compare our simulated velocity fields and direct images with rotation curves from VLT/FORS spectroscopy and ACS images of a cluster at z=0.53 and find remarkable similarities.Comment: 13 pages, 14 figures, accepted for publication in A&A, some improvements and changes, main conclusions are unaffecte

X-ray measured metallicities of the intra-cluster medium: a good measure for the metal mass?

Aims. We investigate whether X-ray observations map heavy elements in the Intra-Cluster Medium (ICM) well and whether the X-ray observations yield good estimates for the metal mass, with respect to predictions on transport mech- anisms of heavy elements from galaxies into the ICM. We further test the accuracy of simulated metallicity maps. Methods. We extract synthetic X-ray spectra from N-body/hydrodynamic simulations including metal enrichment pro- cesses, which we then analyse with the same methods as are applied to observations. By changing the metal distribution in the simulated galaxy clusters, we investigate the dependence of the overall metallicity as a function of the metal distribution. In addition we investigate the difference of X-ray weighted metal maps produced by simulations and metal maps extracted from artifcial X-ray spectra, which we calculate with SPEX2.0 and analyse with XSPEC12.0. Results. The overall metallicity depends strongly on the distribution of metals within the galaxy cluster. The more inhomogeneously the metals are distributed within the cluster, the less accurate is the metallicity as a measure for the true metal mass. The true metal mass is generally underestimated by X-ray observations. The difference between the X-ray weighted metal maps and the metal maps from synthetic X-ray spectra is on average less than 7% in the temperature regime above T > 3E7 K, i.e. X-ray weighted metal maps can be well used for comparison with observed metal maps. Extracting the metal mass in the central parts (r < 500 kpc) of galaxy clusters with X-ray observations results in metal mass underestimates up to a factor of three.Comment: 7 pages, 9 figures, accepted for publication in A&

Submillimeter detection of the Sunyaev -- Zel'dovich effect toward the most luminous X-ray cluster at z=0.45

We report on the detection of the Sunyaev -- Zel'dovich (SZ) signals toward the most luminous X-ray cluster RXJ1347-1145 at Nobeyama Radio Observatory (21 and 43 GHz) and at James Clerk Maxwell Telescope (350 GHz). In particular the latter is the first successful detection of the SZ temperature increment in the submillimeter band which resolved the profile of a cluster of galaxies. Both the observed spectral dependence and the radial profile of the SZ signals are fully consistent with those expected from the X-ray observation of the cluster. The combined analysis of 21GHz and 350GHz data reproduces the temperature and core-radius of the cluster determined with the ROSAT and ASCA satellites when we adopt the slope of the density profile from the X-ray observations. Therefore our present data provide the strongest and most convincing case for the detection of the submillimeter SZ signal from the cluster, as well as in the Rayleigh -- Jeans regime. We also discuss briefly the cosmological implications of the present results.Comment: 11 pages, The Astrophysical Journal (Letters), in pres