Evolution in the iron abundance of the ICM

We present a Chandra analysis of the X-ray spectra of 56 clusters of galaxies at $z>0.3$, which cover a temperature range of $3> kT > 15$ keV. Our analysis is aimed at measuring the iron abundance in the ICM out to the highest redshift probed to date. We find that the emission-weighted iron abundance measured within $(0.15-0.3) R_{vir}$ in clusters below 5 keV is, on average, a factor of $\sim2$ higher than in hotter clusters, following $Z(T)\simeq 0.88 T^{-0.47} Z_\odot$, which confirms the trend seen in local samples. We made use of combined spectral analysis performed over five redshift bins at $0.3> z > 1.3$ to estimate the average emission weighted iron abundance. We find a constant average iron abundance $Z_{Fe}\simeq 0.25 Z_\odot$ as a function of redshift, but only for clusters at $z>0.5$. The emission-weighted iron abundance is significantly higher ($Z_{Fe}\simeq0.4 Z_\odot$) in the redshift range $z\simeq0.3-0.5$, approaching the value measured locally in the inner $0.15 R_{vir}$ radii for a mix of cool-core and non cool-core clusters in the redshift range $0.1<z<0.3$. The decrease in $Z_{Fe}$ with $z$ can be parametrized by a power law of the form $\sim(1+z)^{-1.25}$. The observed evolution implies that the average iron content of the ICM at the present epoch is a factor of $\sim2$ larger than at $z\simeq 1.2$. We confirm that the ICM is already significantly enriched ($Z_{Fe}\simeq0.25 Z_\odot$) at a look-back time of 9 Gyr. Our data provide significant constraints on the time scales and physical processes that drive the chemical enrichment of the ICM.Comment: 4 pages, 4 figures, to appear in the Proceedings of "The Extreme Universe in the Suzaku Era", Dicember 2006, Kyoto (Japan

Hard x-ray broad band Laue lenses (80 - 600 keV): building methods and performances

We present the status of the laue project devoted to develop a technology for building a 20 meter long focal length Laue lens for hard x-/soft gamma-ray astronomy (80 - 600 keV). The Laue lens is composed of bent crystals of Gallium Arsenide (GaAs, 220) and Germanium (Ge, 111), and, for the first time, the focusing property of bent crystals has been exploited for this field of applications. We show the preliminary results concerning the adhesive employed to fix the crystal tiles over the lens support, the positioning accuracy obtained and possible further improvements. The Laue lens petal that will be completed in a few months has a pass band of 80 - 300 keV and is a fraction of an entire Laue lens capable of focusing X-rays up to 600 keV, possibly extendable down to 20 - 30 keV with suitable low absorption crystal materials and focal length. The final goal is to develop a focusing optics that can improve the sensitivity over current telescopes in this energy band by 2 orders of magnitude

Experimental Realization of Optimal Noise Estimation for a General Pauli Channel

We present the experimental realization of the optimal estimation protocol for a Pauli noisy channel. The method is based on the generation of 2-qubit Bell states and the introduction of quantum noise in a controlled way on one of the state subsystems. The efficiency of the optimal estimation, achieved by a Bell measurement, is shown to outperform quantum process tomography

The Brera Multi-scale Wavelet (BMW) ROSAT HRI source catalog. I: the algorithm

We present a new detection algorithm based on the wavelet transform for the analysis of high energy astronomical images. The wavelet transform, due to its multi-scale structure, is suited for the optimal detection of point-like as well as extended sources, regardless of any loss of resolution with the off-axis angle. Sources are detected as significant enhancements in the wavelet space, after the subtraction of the non-flat components of the background. Detection thresholds are computed through Monte Carlo simulations in order to establish the expected number of spurious sources per field. The source characterization is performed through a multi-source fitting in the wavelet space. The procedure is designed to correctly deal with very crowded fields, allowing for the simultaneous characterization of nearby sources. To obtain a fast and reliable estimate of the source parameters and related errors, we apply a novel decimation technique which, taking into account the correlation properties of the wavelet transform, extracts a subset of almost independent coefficients. We test the performance of this algorithm on synthetic fields, analyzing with particular care the characterization of sources in poor background situations, where the assumption of Gaussian statistics does not hold. For these cases, where standard wavelet algorithms generally provide underestimated errors, we infer errors through a procedure which relies on robust basic statistics. Our algorithm is well suited for the analysis of images taken with the new generation of X-ray instruments equipped with CCD technology which will produce images with very low background and/or high source density.Comment: 8 pages, 6 figures, ApJ in pres

Tracing the evolution in the iron content of the ICM

We present a Chandra analysis of the X-ray spectra of 56 clusters of galaxies at z>0.3, which cover a temperature range of 3>kT>15 keV. Our analysis is aimed at measuring the iron abundance in the ICM out to the highest redshift probed to date. We find that the emission-weighted iron abundance measured within (0.15-0.3)R_vir in clusters below 5 keV is, on average, a factor of ~2 higher than in hotter clusters, following Z(T)~0.88T^-(0.47)Z_o, which confirms the trend seen in local samples. We made use of combined spectral analysis performed over five redshift bins at 0.3>z>1.3 to estimate the average emission weighted iron abundance. We find a constant average iron abundance Z_Fe~0.25Z_o as a function of redshift, but only for clusters at z>0.5. The emission-weighted iron abundance is significantly higher (Z_Fe~0.4Z_o) in the redshift range z~0.3-0.5, approaching the value measured locally in the inner 0.15R_vir radii for a mix of cool-core and non cool-core clusters in the redshift range 0.1<z<0.3. The decrease in Z_Fe with redshift can be parametrized by a power law of the form ~(1+z)^(-1.25). The observed evolution implies that the average iron content of the ICM at the present epoch is a factor of ~2 larger than at z=1.2. We confirm that the ICM is already significantly enriched (Z_Fe~0.25Z_o) at a look-back time of 9 Gyr. Our data provide significant constraints on the time scales and physical processes that drive the chemical enrichment of the ICM.Comment: 6 pages, 6 figures, to appear in the Proceedings of "Heating vs. Cooling in Galaxies and Clusters of Galaxies", August 2006, Garching (Germany

Calculation of the Alpha--Particle Ground State within the Hyperspherical Harmonic Basis

The problem of calculating the four--nucleon bound state properties for the case of realistic two- and three-body nuclear potentials is studied using the hyperspherical harmonic (HH) approach. A careful analysis of the convergence of different classes of HH functions has been performed. A restricted basis is chosen to allow for accurate estimates of the binding energy and other properties of the 4He ground state. Results for various modern two-nucleon and two- plus three-nucleon interactions are presented. The 4He asymptotic normalization constants for separation in 2+2 and 1+3 clusters are also computed.Comment: 29 pages, 4 figures, 11 tables, revtex

The sub-mJy radio sky in the Extended Chandra Deep Field South: source population

The sub-mJy radio population is a mixture of active systems, that is star forming galaxies (SFGs) and active galactic nuclei (AGNs). We study a sample of 883 radio sources detected at 1.4 GHz in a deep Very Large Array survey of the Extended Chandra Deep Field South (E-CDFS) that reaches a best rms sensitivity of 6 microJy. We have used a simple scheme to disentangle SFGs, radio-quiet (RQ), and radio-loud (RL) AGNs based on the combination of radio data with Chandra X-ray data and mid-infrared observations from Spitzer. We find that at flux densities between about 30 and 100 microJy the radio population is dominated by SFGs (~60%) and that RQ AGNs become increasingly important over RL ones below 100 microJy. We also compare the host galaxy properties of the three classes in terms of morphology, optical colours and stellar masses. Our results show that both SFG and RQ AGN host galaxies have blue colours and late type morphology while RL AGNs tend to be hosted in massive red galaxies with early type morphology. This supports the hypothesis that radio emission in SFGs and RQ AGNs mainly comes from the same physical process: star formation in the host galaxy.Comment: 13 pages, 11 figures, 1 table, accepted for publication in MNRA

The micro-Jy Radio Source Population: the VLA-CDFS View

We analyse the 267 radio sources from our deep (flux limit of 42 microJy at the field center at 1.4 GHz) Chandra Deep Field South 1.4 and 5 GHz VLA survey. The radio population is studied by using a wealth of multi-wavelength information, including morphology and spectral types, in the radio, optical, and X-ray bands. The availability of redshifts for ~ 70% of our sources allows us to derive reliable luminosity estimates for the majority of the objects. Contrary to some previous results, we find that star-forming galaxies make up only a minority (~ 1/3) of sub-mJy sources, the bulk of which are faint radio galaxies, mostly of the Fanaroff-Riley I type.Comment: 6 pages, 3 figures, to appear in the proceedings of "At the Edge of the Universe", Sintra, Portugal, Oct. 9 - 13, 200