A2163: Merger events in the hottest Abell galaxy cluster II. Subcluster accretion with galaxy-gas separation

Located at z = 0.203, A2163 is a rich galaxy cluster with an intra-cluster medium (ICM) that exhibits extraordinary properties, including an exceptionally high X-ray luminosity, average temperature, and a powerful and extended radio halo. The irregular and complex morphology of its gas and galaxy structure suggests that this cluster has recently undergone major merger events that involve two or more cluster components. In this paper, we study the gas structure and dynamics by means of spectral-imaging analysis of X-ray data obtained from XMM-Newton and Chandra observations. From the evidence of a cold front, we infer the westward motion of a cool core across the E-W elongated atmosphere of the main cluster A2163-A. Located close to a galaxy over-density, this gas 'bullet' appears to have been spatially separated from its galaxy (and presumably dark matter component) as a result of high-velocity accretion. From gas brightness and temperature profile analysis performed in two opposite regions of the main cluster, we show that the ICM has been adiabatically compressed behind the crossing 'bullet' possibly because of shock heating, leading to a strong departure of the ICM from hydrostatic equilibrium in this region. Assuming that the mass estimated from the Yx proxy best indicates the overall mass of the system and that the western cluster sector is in approximate hydrostatic equilibrium before subcluster accretion, we infer a merger scenario between two subunits of mass ratio 1:4, leading to a present total system mass of M500 $\propto 1.9 \times 1015 M_{\odot}$. The exceptional properties of A2163 present various similarities with those of 1E0657-56, the so-called 'bullet-cluster'. These similarities are likely to be related to a comparable merger scenario.Comment: A&A, in pres

Axisymmetric solitary waves on the surface of a ferrofluid

We report the first observation of axisymmetric solitary waves on the surface of a cylindrical magnetic fluid layer surrounding a current-carrying metallic tube. According to the ratio between the magnetic and capillary forces, both elevation and depression solitary waves are observed with profiles in good agreement with theoretical predictions based on the magnetic analogue of the Korteweg-deVries equation. We also report the first measurements of the velocity and the dispersion relation of axisymmetric linear waves propagating on the cylindrical ferrofluid layer that are found in good agreement with theoretical predictions.Comment: to be published in Phys. Rev. Let

X-MAS2: Study Systematics on the ICM Metallicity Measurements

(Abridged)The X-ray measurements of the ICM metallicity are becoming more frequent due to the availability of powerful X-ray telescope with excellent spatial and spectral resolutions. The information which can be extracted from the measurements of the alpha-elements, like Oxygen, Magnesium and Silicon with respect to the Iron abundance is extremely important to better understand the stellar formation and its evolutionary history. In this paper we investigate possible source of bias connected to the plasma physics when recovering metal abundances from X-ray spectra. To do this we analyze 6 simulated galaxy clusters processed through the new version of our X-ray MAp Simulator, which allows to create mock XMM-Newton EPIC MOS1 and MOS2 observations. By comparing the spectroscopic results to the input values we find that: i) Fe is recovered with high accuracy for both hot (T>3 keV) and cold (T<2 keV) systems; at intermediate temperatures, however, we find a systematic overestimate which depends on the number counts; ii) O is well recovered in cold clusters, while in hot systems its measure may overestimate by a factor up to 2-3; iii) Being a weak line, the measurement of Mg is always difficult; despite of this, for cold systems (T<2 keV) we do not find any systematic behavior, while for very hot systems (T>5 keV) the spectroscopic measurement may be strongly overestimated up to a factor of 4; iv) Si is well recovered for all the clusters in our sample. We investigate in detail the nature of the systematic effects and biases found. We conclude that they are mainly connected with the multi-temperature nature of the projected observed spectra and to the intrinsic limitation of the XMM-Newton EPIC spectral resolution that does not always allow to disentangle among the emission lines produced by different elements.Comment: (e.g.: 17 pages, 8 figures, accepted for publication in the Astrophysical Journal, updated discussion to match published version-new section:6.3

Interdisciplinary Medication Adherence Program: The Example of a University Community Pharmacy in Switzerland.

The Community Pharmacy of the Department of Ambulatory Care and Community Medicine (Policlinique Médicale Universitaire, PMU), University of Lausanne, developed and implemented an interdisciplinary medication adherence program. The program aims to support and reinforce medication adherence through a multifactorial and interdisciplinary intervention. Motivational interviewing is combined with medication adherence electronic monitors (MEMS, Aardex MWV) and a report to patient, physician, nurse, and other pharmacists. This program has become a routine activity and was extended for use with all chronic diseases. From 2004 to 2014, there were 819 patient inclusions, and 268 patients were in follow-up in 2014. This paper aims to present the organization and program's context, statistical data, published research, and future perspectives

Merging history of three bimodal clusters

We present a combined X-ray and optical analysis of three bimodal galaxy clusters selected as merging candidates at z ~ 0.1. These targets are part of MUSIC (MUlti--Wavelength Sample of Interacting Clusters), which is a general project designed to study the physics of merging clusters by means of multi-wavelength observations. Observations include spectro-imaging with XMM-Newton EPIC camera, multi-object spectroscopy (260 new redshifts), and wide-field imaging at the ESO 3.6m and 2.2m telescopes. We build a global picture of these clusters using X-ray luminosity and temperature maps together with galaxy density and velocity distributions. Idealized numerical simulations were used to constrain the merging scenario for each system. We show that A2933 is very likely an equal-mass advanced pre-merger ~ 200 Myr before the core collapse, while A2440 and A2384 are post-merger systems ~ 450 Myr and ~1.5 Gyr after core collapse, respectively). In the case of A2384, we detect a spectacular filament of galaxies and gas spreading over more than 1 h^{-1} Mpc, which we infer to have been stripped during the previous collision. The analysis of the MUSIC sample allows us to outline some general properties of merging clusters: a strong luminosity segregation of galaxies in recent post-mergers; the existence of preferential axes --corresponding to the merging directions-- along which the BCGs and structures on various scales are aligned; the concomitance, in most major merger cases, of secondary merging or accretion events, with groups infalling onto the main cluster, and in some cases the evidence of previous merging episodes in one of the main components. These results are in good agreement with the hierarchical scenario of structure formation, in which clusters are expected to form by successive merging events, and matter is accreted along large--scale filaments

The distant galaxy cluster CL0016+16: X-ray analysis up to R200R_{200}

To study the mass distribution of galaxy clusters up to their Virial radius, CL0016+16 seems to be a good candidate,since it is a bright massive cluster, previously considered as being dynamically relaxed. Using XMM-Newton observations of CL0016+16, we performed a careful X-ray background analysis, and we detected convincingly its X-ray emission up to $R_{200}$. We then studied its dynamical state with a detailed 2D temperature and surface brightness analysis of the inner part of the cluster. Using the assumption of both spherical symmetry and hydrostatic equilibrium (HE) we can determine the main cluster parameters: total mass, temperature profile, surface brightness profile and $\beta$-parameter. We also build a temperature map which clearly exhibits departure from spherical symmetry in the centre. To estimate the influence of these perturbations onto our total mass estimate, we also compute the total mass in the framework of the HE approach, but this time with various temperature profiles obtained in different directions. These various total mass estimates are consistent with each other. The temperature perturbations are clear signatures of ongoing merger activity. We also find significant residuals after subtracting the emissivity map by a 2D $\beta$-model fit. We conclude that, although CL0016+16 shows clear signs of merger activity and departure from spherical symmetry in the centre, its X-ray emissivity can be detected up to $R_{200}$ and the corresponding mass $M_{200}$ can be computed directly. It is therefore a good candidate to study cosmological scaling laws as predicted by the theory.Comment: 11 pages, 17 figures, Accepted for publication in A&

Solar Magnetoseismology with Magnetoacoustic Surface Waves in Asymmetric Magnetic Slab Waveguides

Solar magnetoseismology is an indirect method to approximate plasma parameters that are traditionally difficult to measure in the solar atmosphere using observations of magnetohydrodynamic waves. A magnetic slab can act as waveguide for magnetoacoustic waves that approximates magnetic structures in the solar atmosphere. The asymmetry of the slab caused by different plasma parameters in each external region affects both the eigenfrequencies and eigenfunctions differently at each side of the slab, that is, both the temporal and spatial profiles of the eigenmodes of propagation along the slab are influenced by the equilibrium asymmetry. We present two novel diagnostic tools for solar magnetoseismology that use this distortion to estimate the slab magnetic field strength using the spatial distribution of magnetoacoustic surface waves: the amplitude ratio and the minimum perturbation shift techniques. They have the potential to estimate background equilibrium parameters in inhomogeneous solar structures such as elongated magnetic bright points, prominences, and the clusters of magnetic brightenings rooted in sunspot light bridges known as light bridge surges or light walls, which may be locally approximated as slabs

A Multi-Wavelength Mass Analysis of RCS2 J232727.6-020437, a ~3x1015^{15}M⊙_{\odot} Galaxy Cluster at z=0.7

We present an initial study of the mass and evolutionary state of a massive and distant cluster, RCS2 J232727.6-020437. This cluster, at z=0.6986, is the richest cluster discovered in the RCS2 project. The mass measurements presented in this paper are derived from all possible mass proxies: X-ray measurements, weak-lensing shear, strong lensing, Sunyaev Zel'dovich effect decrement, the velocity distribution of cluster member galaxies, and galaxy richness. While each of these observables probe the mass of the cluster at a different radius, they all indicate that RCS2 J232727.6-020437 is among the most massive clusters at this redshift, with an estimated mass of M_200 ~3 x10^15 h^-1 Msun. In this paper, we demonstrate that the various observables are all reasonably consistent with each other to within their uncertainties. RCS2 J232727.6-020437 appears to be well relaxed -- with circular and concentric X-ray isophotes, with a cool core, and no indication of significant substructure in extensive galaxy velocity data.Comment: 19 pages, 15 figures, submitted to ApJ on March 5, 2015; in press. Manuscript revised following the referee revie

Tara Pacific Expedition\u27s atmospheric measurements of marine aerosols across the Atlantic and Pacific Oceans: Overview and preliminary results

Marine aerosols play a significant role in the global radiative budget, in clouds\u27 processes, and in the chemistry of the marine atmosphere. There is a critical need to better understand their production mechanisms, composition, chemical properties, and the contribution of ocean-derived biogenic matter to their mass and number concentration. Here we present an overview of a new dataset of in situ measurements of marine aerosols conducted over the 2.5-yr Tara Pacific Expedition over 110, 000 km across the Atlantic and Pacific Oceans. Preliminary results are presented here to describe the new dataset that will be built using this novel set of measurements. It will characterize marine aerosols properties in detail and will open a new window to study the marine aerosol link to the water properties and environmental conditions