Suzaku observations of X-ray excess emission in the cluster of galaxies A3112

We analysed the Suzaku XIS1 data of the A3112 cluster of galaxies in order to examine the X-ray excess emission in this cluster reported earlier with the XMM-Newton and Chandra satellites. The best-fit temperature of the intracluster gas depends strongly on the choice of the energy band used for the spectral analysis. This proves the existence of excess emission component in addition to the single-temperature MEKAL in A3112. We showed that this effect is not an artifact due to uncertainties of the background modeling, instrument calibration or the amount of Galactic absorption. Neither does the PSF scatter of the emission from the cool core nor the projection of the cool gas in the cluster outskirts produce the effect. Finally we modeled the excess emission either by using an additional MEKAL or powerlaw component. Due to the small differencies between thermal and non-thermal model we can not rule out the non-thermal origin of the excess emission based on the goodness of the fit. Assuming that it has a thermal origin, we further examined the Differential Emission Measure (DEM) models. We utilised two different DEM models, a Gaussian differential emission measure distribution (GDEM) and WDEM model, where the emission measure of a number of thermal components is distributed as a truncated power law. The best-fit XIS1 MEKAL temperature for the 0.4-7.0 keV band is 4.7+-0.1 keV, consistent with that obtained using GDEM and WDEM models.Comment: 8 pages, 10 figures, accepted to A&

X-ray total mass estimate for the nearby relaxed cluster A3571

We constrain the total mass distribution in the cluster A3571, combining spatially resolved ASCA temperature data with ROSAT imaging data with the assumption that the cluster is in hydrostatic equilibrium. The total mass within r_500 (1.7/h_50 Mpc) is M_500 = 7.8[+1.4,-2.2] 10^14/ h_50 Msun at 90% confidence, 1.1 times smaller than the isothermal estimate. The Navarro, Frenk & White ``universal profile'' is a good description of the dark matter density distribution in A3571. The gas density profile is shallower than the dark matter profile, scaling as r^{-2.1} at large radii, leading to a monotonically increasing gas mass fraction with radius. Within r_500 the gas mass fraction reaches a value of f_gas = 0.19[+0.06,-0.03] h_50^{-3/2} (90% confidence errors). Assuming that this value of f_gas is a lower limit for the the universal value of the baryon fraction, we estimate the 90% confidence upper limit of the cosmological matter density to be Omega_m < 0.4.Comment: 10 pages, 4 figures, accepted by Ap

The Baryonic and Dark Matter Distributions in Abell 401

We combine spatially resolved ASCA temperature data with ROSAT imaging data to constrain the total mass distribution in the cluster A401, assuming that the cluster is in hydrostatic equilibrium. We obtain a total mass within the X-ray core (290/h_50 kpc) of 1.2[+0.1,-0.5] 10^14 /h_50 Msun at the 90% confidence level, 1.3 times larger than the isothermal estimate. The total mass within r_500 (1.7/h_50 Mpc) is M_500 = 0.9[+0.3,-0.2] 10^15/ h_50 Msun at 90% confidence, in agreement with the optical virial mass estimate, and 1.2 times smaller than the isothermal estimate. Our M_500 value is 1.7 times smaller than that estimated using the mass-temperature scaling law predicted by simulations. The best fit dark matter density profile scales as r^{-3.1} at large radii, which is consistent with the Navarro, Frenk & White (NFW) ``universal profile'' as well as the King profile of the galaxy density in A401. From the imaging data, the gas density profile is shallower than the dark matter profile, scaling as r^{-2.1} at large radii, leading to a monotonically increasing gas mass fraction with radius. Within r_500 the gas mass fraction reaches a value of f_gas = 0.21[+0.06,-0.05] h_50^{-3/2} (90% confidence errors). Assuming that f_gas (plus an estimate of the stellar mass) is the universal value of the baryon fraction, we estimate the 90% confidence upper limit of the cosmological matter density to be Omega_m < 0.31.Comment: 17 pages, 6 figures, accepted by Ap

Mine-action Challenges and Responses in Georgia

Following an international conflict in 2008, Georgia faces a greater threat from landmines and explosive remnants of war than that posed by previous violence. In response to this threat, Georgia, with assistance provided by the Office of Weapons Removal and Abatement in the U.S. Department of State’s Bureau of Political-Military Affairs (PM/WRA) and the Government of Canada, created national bodies to coordinate and implement landmine and ERW clearance. This article documents Georgia’s past ERW, landmine and cluster-munitions contamination, as well as efforts to remove these threats

Revisiting the soft X-ray excess emission in clusters of galaxies observed with XMM-Newton

We analyze four XMM-Newton galaxy clusters in order to test whether their soft X-ray excess emission in the 0.2-0.5 keV band as reported by Kaastra et al. (2003) maintains after the application of the current knowledge of the XMM-Newton background and calibration. We show that in the bright central 500 kpc regions the details of the background modeling are insignificant. Thus, the cluster soft excess is not a background artifact, contrary to recent claims by Bregman et al. (2006). We find evidence that the change in PN calibration between years 2002 and 2005 results in significant decrease of the soft excess signal. However, the MOS instruments measure significant amounts of soft excess, or sub-Galactic NH. These differences are compatible with the current level of uncertainty in the calibration of both instruments.Comment: ApJ in press, minor stylistic change

The XMM-Newton EPIC Background and the production of Background Blank Sky Event Files

We describe in detail the nature of XMM-Newton EPIC background and its various complex components, summarising the new findings of the XMM-Newton EPIC background working group, and provide XMM-Newton background blank sky event files for use in the data analysis of diffuse and extended sources. Blank sky event file data sets are produced from the stacking of data, taken from 189 observations resulting from the Second XMM-Newton Serendipitous Source Catalogue (2XMMp) reprocessing. The data underwent several filtering steps, using a revised and improved method over previous work, which we describe in detail. We investigate several properties of the final blank sky data sets. The user is directed to the location of the final data sets. There is a final data set for each EPIC instrument-filter-mode combination.Comment: Paper accepted by A&A 22 December 2006. 14 pages, 8 figures. Paper can also be found at http://www.star.le.ac.uk/~jac48/publications