Skywalking GEMS and UDF

The two large colour mosaics of the GEMS and UDF projects, both obtained with the Hubble Space Telescope and ACS, consist of large amounts of data. We present two web application pages (the GEMS and UDF "Skywalker") that allow to pan around in these mosaics with downloading only small parts at a time.Comment: 1 pag

Chandra and optical/IR observations of CXOJ1415.2+3610, a massive, newly discovered galaxy cluster at z~1.5

(Abridged) We report the discovery of CXO J1415.2+3610, a distant (z~1.5) galaxy cluster serendipitously detected in a deep, high-resolution Chandra observation targeted to study the cluster WARP J1415.1+3612 at z=1.03. This is the highest-z cluster discovered with Chandra so far. Moreover, the total exposure time of 280 ks with ACIS-S provides the deepest X-ray observation currently achieved on a cluster at z>1.5. We perform an X-ray spectral fit of the extended emission of the intracluster medium (ICM) with XSPEC, and we detect at a 99.5% confidence level the rest frame 6.7-6.9 keV Iron K_\alpha line complex, from which we obtain z_X=1.46\pm0.025. The analysis of the z-3.6\mu m color-magnitude diagram shows a well defined sequence of red galaxies within 1' from the cluster X-ray emission peak with a color range [5 < z-3.6 \mu m < 6]. The photometric redshift obtained by spectral energy distribution (SED) fitting is z_phot=1.47\pm 0.25. After fixing the redshift to z=1.46, we perform the final spectral analysis and measure the average gas temperature with a 20% error, kT=5.8^{+1.2}_{-1.0} keV, and the Fe abundance Z_Fe = 1.3_{-0.5}^{+0.8}Z_\odot. We fit the background subtracted surface brightness with a single beta--model out to 35" and derive the deprojected electron density profile. The ICM mass is 1.09_{-0.2}^{+0.3}\times 10^{13} M_\odot within 300 kpc. The total mass is M_{2500}= 8.6_{-1.7}^{+2.1} \times 10 ^{13} M_\odot for R_{2500}=(220\pm 55) kpc. Extrapolating the profile at larger radii we find M_{500}= 2.1_{-0.5}^{+0.7} \times 10 ^{14} M_\odot for R_{500} = 510_{-50}^{+55}$ kpc. This analysis establishes CXOJ1415.2+3610 as one of the best characterized distant galaxy clusters based on X-ray data alone.Comment: 12 pages, 9 figures, A\&A in press, minor modifications in the tex

Euclidean Thermal Green Functions of Photons in Generalized Euclidean Rindler Spaces for any Feynman-like Gauge

The thermal Euclidean Green functions for Photons propagating in the Rindler wedge are computed employing an Euclidean approach within any covariant Feynman-like gauge. This is done by generalizing a formula which holds in the Minkowskian case. The coincidence of the found (\be=2\pi)-Green functions and the corresponding Minkowskian vacuum Green functions is discussed in relation to the remaining static gauge ambiguity already found in previous papers. Further generalizations to more complicated manifolds are discussed. Ward identities are verified in the general case.Comment: 12 pages, standard latex, no figures, some signs changed, more comments added, final version to appear on Int. J. Mod. Phys.

Probing the massive star forming environment - a multiwavelength investigation of the filamentary IRDC G333.73+0.37

We present a multiwavelength study of the filamentary infrared dark cloud (IRDC) G333.73+0.37. The region contains two distinct mid-infrared sources S1 and S2 connected by dark lanes of gas and dust. Cold dust emission from the IRDC is detected at seven wavelength bands and we have identified 10 high density clumps in the region. The physical properties of the clumps such as temperature: 14.3-22.3 K and mass: 87-1530 M_sun are determined by fitting a modified blackbody to the spectral energy distribution of each clump between 160 micron and 1.2 mm. The total mass of the IRDC is estimated to be $~4700 M_sun. The molecular line emission towards S1 reveals signatures of protostellar activity. Low frequency radio emission at 1300 and 610 MHz is detected towards S1 (shell-like) and S2 (compact morphology), confirming the presence of newly formed massive stars in the IRDC. Photometric analysis of near and mid-infrared point sources unveil the young stellar object population associated with the cloud. Fragmentation analysis indicates that the filament is supercritical. We observe a velocity gradient along the filament, that is likely to be associated with accretion flows within the filament rather than rotation. Based on various age estimates obtained for objects in different evolutionary stages, we attempt to set a limit to the current age of this cloud.Comment: 26 pages, 20 figures, accepted by Ap

Experimental violation of a Bell-like inequality with optical vortex beams

Optical beams with topological singularities have a Schmidt decomposition. Hence, they display features typically associated with bipartite quantum systems; in particular, these classical beams can exhibit entanglement. This classical entanglement can be quantified by a Bell inequality formulated in terms of Wigner functions. We experimentally demonstrate the violation of this inequality for Laguerre-Gauss (LG) beams and confirm that the violation increases with increasing orbital angular momentum. Our measurements yield negativity of the Wigner function at the origin for \LG_{10} beams, whereas for \LG_{20} we always get a positive value.Comment: 6 pages, 4 eps-color figures. Comments welcome

Spontaneous formation of optically induced surface relief gratings

A model based on Fick's law of diffusion as a phenomenological description of the molecular motion, and on the coupled mode theory, is developped to describe single-beam surface relief grating formation in azopolymers thin films. It allows to explain the mechanism of spontaneous patterning, and self-organization. It allows also to compute the surface relief profile and its evolution in time with good agreement with experiments

Evidence for a cosmological effect in \gamma-ray spectra of BL Lacs

We update the list of GeV-TeV extragalactic \gamma-ray sources using the 2-year catalog from the Fermi-LAT and recent results ground-based \gamma-ray telescopes. Breaks in the spectra between the high energy (100 MeV <E< 300 GeV) and the very high energy (E> 200 GeV) ranges, and their dependence on distance, are discussed in the context of absorption on the extragalactic background light (EBL). We calculate the size of the expected break using a model for the EBL and compare it to the data taking into account systematic uncertainties in the measurements. We develop a novel Bayeasian model to describe this dataset and use it to constrain two simple models for the EBL-induced breaks.Comment: accepted for publication in A&

Continuous Time Random Walks in periodic systems: fluid limit and fractional differential equations on the circle

In this article, the continuous time random walk on the circle is studied. We derive the corresponding generalized master equation and discuss the effects of topology, especially important when Levy flights are allowed. Then, we work out the fluid limit equation, formulated in terms of the periodic version of the fractional Riemann-Liouville operators, for which we provide explicit expressions. Finally, we compute the propagator in some simple cases. The analysis presented herein should be relevant when investigating anomalous transport phenomena in systems with periodic dimensions.Comment: 14 pages, 1 figure. References added. Published versio

Controlling the Spin Polarization of the Electron Current in a Semimagnetic Resonant-Tunneling Diode

The spin filtering effect of the electron current in a double-barrier resonant-tunneling diode (RTD) consisting of ZnMnSe semimagnetic layers has been studied theoretically. The influence of the distribution of the magnesium ions on the coefficient of the spin polarization of the electron current has been investigated. The dependence of the spin filtering degree of the electron current on the external magnetic field and the bias voltage has been obtained. The effect of the total spin polarization of the electron current has been predicted. This effect is characterized by total suppression of the spin-up component of electron current, that takes place when the Fermi level coincides with the lowest Landau level for spin-up electrons in the RTD semimagnetic emitter