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In the framework of a five year plan the Italian Space Agency has started a national program of small scientific satellites. The first two, AGILE and DAVID are already at an advanced stage of development. The former is dedicated to Gamma Ray Astrophysics, the latter to communication technology and engineering development. A third mission, to be devoted to Earth Science and exploration is in the process of being defined. A general view of the program and some specific features of the missions selected so far are given

A method of searching for multiplets in a large catalogue of galaxies with measured redshifts is described. Compact Groups samples having different local and global characteristics are generated when the algorithm is applied to ZCAT catalogue. Both local and environmental galaxy density have been computed thus allowing to define truly isolated compact groups as well as compact groups in dense and medium dense environments. We find 40% of our compact groups to be isolated while as much as 20% are identified in high density structures.

We performed a blind search for blue‐shifted Fe K absorption lines at energies greater than 6 keV in the X‐ray spectra of a sample of 44 radio‐quiet AGNs observed with XMM‐Newton. We statistically quantified the parameters and the incidence of such lines and also determined their detection significance through extensive Monte Carlo simulations. This allows us to define their global veracity and to overcome the reported publication bias. These findings suggest the presence of previously unknown ultra‐fast outflows in radio‐quiet AGNs.

The present work shows a quantitative trade-off analysis of the Simbol-X Mirror Spacecraft (MSC) passive shielding, in the phase space of the various parameters: mass budget, dimension, geometry, and composition. A simplified physical (and geometrical) model of the sky screen, implemented by means of a GEANT4 simulation, has been developed to perform a performance-driven mass optimization and evaluate the residual background level on Simbol-X focal plane., Comment: 3 pages, 6 figures, to appear in the proceedings of the second Simbol-X International Symposium "Simbol-X - Focusing on the Hard X-ray Universe", AIP Conf. Proc. Series, P. Ferrando and J. Rodriguez eds

Fanaroff & Riley type II radio galaxies (FRII) are complex objects. In particular FRII Narrow Line Radio Galaxies (NLRG), optically classified as High Excitation Galaxies (HEG) show X‐ray spectra very similar to their radio‐quiet counterparts, the Seyfert 2 galaxies. They show 2–10 keV continua heavily obscured (NH∼1023–24 cm−2) and intense FeKα lines, typical cold matter reprocessing features. Moreover recent Chandra and XMM‐Newton observations suggest that the soft X‐ray emission of HEG and Seyfert 2 have a common origin from photoionized gas, reinforcing the idea that not only their nuclear engine but also the circumnuclear gas (at least the warm phase) are similar. On the contrary, our knowledge of NLRG HEG above 10 keV is very poor when compared to brighter Seyfert 2. As a consequence, the physical properties of the cold phase of the circumnuclear gas (possibly linked to a dusty torus) are largely unknown. Thanks to its high sensitivity up to 80 keV, Simbol‐X will provide very accurate spectra and wi...

The nature of the hard X‐ray emission above 3 keV of the Galactic Centre (GC) is still source of controversy. Recent observations with Chandra are consistent with either a population of discrete sources or with a diffuse non thermal emission or, most likely, a combination of the two. The Simbol‐X mission will be equipped with a grazing incident telescope imaging up to ∼80 keV, providing an improvement of three orders of magnitude in sensitivity and angular resolution compared with the instruments that have operated so far above 10 keV. This capability will enable to directly disentangle between the discrete source versus the diffuse emission scenarios. This is demonstrated by the Simbol‐X simulations of the GC shown here, where the input model includes a list of both diffuse and point sources (both resolved and unresolved) using the input spectrum observed with presently operating X‐ray telescopes.

There is increasing evidence that quasar outflows may play a key role in providing the feedback between AGN/QSOs and their surrounding (and feeding) media, in regulating the central supermassive black hole growth and the galaxy formation and, on larger scales, in shaping the growth of cosmic structures (see e.g. [1]). X‐ray observations of quasar outflows are crucial to probe their innermost parts and assess the global energetics entrained in the outflow by studying its most extreme (in terms of velocity, ionization state, mass outflow rate) phases. Simbol‐X—with its high effective area in the Fe K energy band and above—will allow the detection and the characterization of powerful outflows in bright, nearby AGN and notably also in moderately faint AGN, thus shedding light on feedback processes in these objects.

We present here the first Simbol‐X simulations of the extended components, lobes and hot spots, of the radio galaxies. We use the paradigmatic case of Pictor A to test the capabilities of Simbol‐X in this field of studies. Simulations demonstrate that Simbol‐X will be able not only to perform spatially resolved studies on the lobes of radio galaxies below 10 keV but also to observe, for the first time, hard X‐ray emission from the hot spots. These extremely promising results show the considerable potentiality of Simbol‐X in studying interaction phenomena between relativistic plasma and surrounding environment.

International audience; The ESA observatory INTEGRAL (International Gamma-Ray Astrophysics Laboratory) is dedicated to fine imaging and spectroscopy in the energy range 15 keV to 10 Mev with concurrent X-ray (3-35 keV) and optical monitoring. It was launched on October 17, 2002 and has been succesfully operating ever since. Its two main instruments the spectrometer SPI - optimized for high resolution spectroscopy - and the imager IBIS - optimized for for high resolution imaging - are complemented by the X-ray monitor JEM-X and the optical monitor OMC. All the high energy instruments use coded mask techniques, allowing imaging in the gamma-ray range and combining wide fields of view with high spatial resolution. The presentation gives an overview of the unique properties of INTEGRAL.

This paper presents new Chandra and BeppoSAX observations aimed at investigating the optical/X-ray mismatch in the enigmatic class of the Composite galaxies, discovered by a cross-correlation of IRAS and ROSAT all sky survey catalogues. These galaxies have been classified as star-forming objects on the basis of their optical spectra, while the detection of weak broad wings in the H(alpha) emission in a few of them and their high X-ray luminosity in the ROSAT band indicated the presence of an active nucleus. The analysis of Chandra observations for 4 Composites has revealed nuclear point-like sources, with a typical AGN spectrum (Gamma = 1.7-1.9) and little intrinsic absorption. A strong flux variability has been observed on different time scales, in particular most of the sources were brighter at the ROSAT epoch. Although of relative low luminosity for the AGN class (L(2-10 keV) = 3-60 x 10^{41} erg/s), the active nucleus is nevertheless dominant in the X-ray domain. At other wavelengths it appears to be overwhelmed by the starburst and/or host galaxy light, yielding the Composite classification for these objects., 20 pages, 10 figures, accepted by ApJ

The Early Data Release of the Sloan Digital Sky Survey (SDSS) contains 150 Narrow-Line Seyfert 1 (NLS1) galaxies, most of them previously unknown. We present here the study of the X-ray emission from two of these active galaxies (SDSS J030639.57+000343.2 and SDSS J141519.50-003021.6), based upon XMM-Newton observations. The spectral and timing characteristics of the two sources are presented and compared against the typical properties of known NLS1 galaxies. We found that these two NLS1 are within the dispersion range of the typical values of this class of AGN, although with some interesting features that deserve further studies., Comment: 5 pages, 8 figures. Accepted for publication on A&A Main Journal

We present the XMM-Newton observation of the merging system IRAS 19254-7245, also known as The Superantennae, whose southern nucleus is classified as a Seyfert 2 galaxy. The XMM-Newton data have allowed us to perform a detailed X-ray imaging and spectral analysis of this system. We clearly detect, for the first time in this system, a strong EW ~ 1.4 keV Fe emission line at 6.49+/-0.1 keV (rest-frame). The X-ray spectrum requires a soft thermal component (kT~0.9 keV; L(0.5-2) ~ 4E41 cgs), likely associated with the starburst, and a hard power-law continuum above 2 keV (observed L(2-10) ~ 4E42 cgs). We confirm the flatness of this latter component, already noted in previous ASCA data. This flatness, together with the detection of the strong Fe-Kalpha line and other broad band indicators, suggest the presence of a Compton-thick AGN with intrinsic luminosity > 1E44 cgs. We show that a Compton-thick model can perfectly reproduce the X-ray spectral properties of this object., 6 pages, 4 figures, Latex manuscript, Accepted for publication in Astronomy and Astrophysics

The LINER nucleus of the nearby spiral galaxy M81 was pointed by BeppoSAX, which caught it at the highest (2–10) keV flux level observed so far. The LECS, MECS and PDS data (extending over 0.1–100 keV) are used to investigate the similarities and differences between LINERs and AGNs. The continuum is well fitted by a power law of photon index Γ∼1.84, modified by little absorption due to cold material; signs of reflection from the optically thick material of an accretion disk are not observed. Instead, BeppoSAX detects a 6.7 keV emission line (confirming an ASCA result), and an absorption edge at ∼8.6 keV. Both spectral features are consistent with being produced by iron at the same high ionization level, and possibly also with the same column density. We suggest that they come from transmission through a highly photoionized medium. The origin of the continuum emission is uncertain, since typical signatures of a standard accretion disk are absent, and the steep spectrum observed over (0.1–100) keV requires ...

Recent BeppoSAX observations of bright radio galaxies have shown that they have a considerable variety of spectral properties and important differences with respect to Seyfert galaxies. Reprocessing features (Fe line and reflection hump) are not always present and generally weak. We suggest two possible scenarios: either radio-loud objects have disk X-ray emission diluted by the jet, or their X-ray reprocessing material subtends a smaller solid angle because of different accretion disk geometry and physical characteristics.

The role played by environment on nuclear activity in galaxies is not clear and largely debated (see e.g. Barnes & Hernquist 1992, Kelm 1996). To overcome statistical uncertainties, environment properties of two large samples of Seyfert galaxies (Sy 1 and Sy 2 have been kept separated) have been computed and compared with equivalent size “normal galaxy” sample ones. Seyfert samples have been extracted from the Veron & Veron catalogue (Veron & Veron 1996), whilst “normal galaxies” have been randomly extracted from ZCAT (Huchra 1993). The samples are limited in cz ([1500–9500] km/sec) and contain 149 Sy 1, 173 Sy 2 and 160 “normal galaxies” (hundreds of random extractions from ZCAT). For each galaxy neighbors have been computed (from ZCAT) within two variables radii, R (isolation radius) and r (pair separation), which span [0.2 – 2] h 100 Mpc. and [20– 90]h 100 kpc. respectively. Neighbors must lie also within 700 km/sec from the galaxy. In this way, for each value of R and r, environment of each galaxy has been “quantified”.

New spectral measurements of the well known HII region Rosette Nebula have been performed with the 32m Medicina (Italy) VLBI single dish [Beamwidth: 5’, beam efficiency: 83%; Tsys ∼ 45K; 1024 channels autocor-relator, bandwith: 12.5MHz, velocity resolution: 0.88Kms-1]. Hydrogen Radio Recombination Lines (RRLs) observations at 8.3 MHz (92α) are useful in attempting to build a non-LTE model for this ring like HII region in order to explain the observed behaviour with frequency of the line to continuum ratio Tl/Tc. Measurements were performed at Celnik’s (1985) positions. Standard spectral fitting and data analysis have led to the values reported in the Table.

A systematic study of 30 Radio Loud AGNs available in the BeppoSAX archive has been carried out. The sample consists of 9 Broad Line radio Galaxies, 5 Steep Spectrum Radio Quasars and 16 Flat Spectrum Radio Quasars. These objects represent, according to Unified Models, objects with decreasing viewing angles. Our analysis shows considerable differences between FSRQs and BLRGs'SSRQS. As expected in the AGN Unified Model: i) the X-Ray spectrum of FSRQs is a simple power law with a hard spectral slope (the only exception being 3C273), ii) Broad Line and Steep Radio Spectrum AGNs show a steeper X-Ray continuum and Seyfert like features. We also find that the Fe line is weaker than in radio quiet objects. However no strong evidence emerges that a jet contamination may be the main responsible for the EW shrinking in BLRGs and SSRQs. Recent XMM-Newton observations of Pictor A, 3C445 and PKS 2152-69 confirm the nuclear BeppoSAX results and better constrain the Fe line parameters.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

We have studied a sample of seven dark clouds (Bok globules) and eight Hergib Ae/Be stars in the J=1 → 0 transition of HCO+, H13CO+, HCN, and H13CN. The most abundant isotopomers were found in almost all the sources (detection rate 70–90%).From the derived physical parameters and column densities it seems that a quite similar scenario applies for the dark clouds and the gas around the Herbig stars. These similarities, together with the already known features from literature, suggest that the presently studied globules are likely to be sites of low‐mass star formation.

The HEAO–1 A2 scanning survey has provided small field-of-view data characterized by a full width zero intensity of 3° along the scan direction (at approximately constant ecliptic longitude λ) and of 6° perpendicular to it. We have used independent fields taken from scanning circles separated by Δλ = 6° and whose centers are separated by Δβ = 3°. After having excluded all fields at | β | < 60° or at | b | ≤ 20°, only 905 of the total turned out to be not significantly contaminated by diffuse galactic emission or by known discrete sources. The flux intensity at each field's central position was evaluated by fitting a point source plus a constant background. The sample average C (θ) of the products dI (θ) x dI'(θ + Δθ) of positive and negative intensity fluctuations computed for angular separations of 3°, 6°, …, and 27° provides the X-ray background (XRB) angular correlation function.

This paper is intended as part of a more extensive molecular line survey in star forming regions along the evolutionary track of a collapsing cloud toward a young stellar object. We have studied a sample of seven small dark clouds (Bok globules) and eight Herbig Ae/Be stars in the J=1->0 transition of HCO$^{+}$, H$^{13}$CO$^{+}$, HCN and H$^{13}$CN. The choice of these molecules is determined by the simple chemistry and the predicted high abundance of the reactants leading to their formation. The isotopically substituted species (isotopomers), H$^{13}$CO$^{+}$ and H$^{13}$CN, were observed in order to determine, whenever possible, the optical thickness of the main species. The most abundant isotopomers were found in almost all the sources (detection rate 70-90\%). Those sources which exhibited the strongest signals were also searched for the $^{13}$C isotopomers. H$^{13}$CO$^{+}$ was found in one dark cloud and around three Herbig Ae/Be stars, while H$^{13}$CN around only one star. The column densities for each species and the physical conditions of the objects were derived whenever the observational data allowed it., 16 pages plus 6 figures available in hardcopy from ggcpalumbo@alma02.cineca.it LaTEX ver. 2.09, BAP 11-1993-036-DDA

Expectations for the angular correlation function of intensity fluctuations of the extragalacitc 2-10 keV X-ray background are discussed in relation to the two-point spatial correlation functions, xi(r), of X-ray sources. A simple analytic formula for the amplitude of intensity correlations, Gamma(theta), holding in the low-redshift, small-separation approximation, is derived. The HEAO 1 A-2 upper limits on Gamma(theta) have been exploited to derive constraints on the local xi(r) functions of rich clusters of galaxies, of AGNs, and on the AGN-cluster cross-correlation, as well as on evolution of the correlation functions with cosmic time. X-ray data are found to be compatible with the Bahcall and Soneira estimates of xi(cluster-cluster) as well as with the results of recent studies of quasar clustering.

X-ray fluxes or upper limits in the 2-10 keV energy band from the HEAO 1 A-2 experiment are given for well-defined samples of QSOs and of Seyfert galaxies of types 1, 1.5 and 2, and for a list of BL Lac objects (334 sources in total). All on-orbit X-ray measurements of these objects published between 1976 and 1986 from other experiments have also been cataloged.

Radio systems with all sky viewing antennas at 151 MHz were operating at 5 widely spaced stations over the period 1970–1973, during which 19 Vela γ-ray bursts were detected. The records were analysed for each Vela time but no radio coincidences were recorded. A new experiment in the radio band operating at 408 MHz with similar objectives is now under construction and will be described. Five radiometers at 10 GHz have been tracking the Perseus cluster of galaxies for over one year. The supernova reported on 1 March in Perseus occurred during our oberving time but failed to give evidence from prompt emission in excess to 8×10−11 erg cm−2 event−1, for event durations 0.3–100 s.

One year's data on radio pulse from EAS at three frequencies (46, 65, 110 MHz) from the Medicina array have been analysed. The dominance of the geomagnetic production mechanism is confirmed. The frequency spectrum between 46 and 65 MHz appears to be flat. The detected electric field strength Ev has been considered as a measure of primary particle energy, and its value is correlated to shower size N and particle density rho at 50 and 100 m from the shower axis in order to study AES longitudinal fluctuations. Errors on each measured quantity are discussed, and it is shown that fluctuations are present.

Final results obtained from the array at Medicina on radioemission from extensive air showers are presented. It is shown that, although not in contradiction with theory, the frequency spectrum and the radio lateral distribution cannot provide information about the primary-cosmic-ray composition, because measurements are taken at small core distances and intrinsic errors are large. If we take the electric-field strengthEν as a measure of the primary energyEp, it is shown that fluctuations of ∼100% are found in shower parameters such as the sizeN and the density ϱ100. The data suggest the presence of protons in the primary cosmic-ray flux at ∼1017 eV. Uncertainties in measurements and in radiopulse production mechanisms are discussed and it is shown that this method alone is not as reliable as was previously predicted.

Between 1972 and 1975 an international collaborative search was carried out for prompt 10 GHz emission at the onset of supernovae. The motivations and techniques involved in this effort are described, and the results of the three years' work are summarized. No pulses from supernovae were detected, the best upper limit being 4×1043 ergs in a 40 MHz band at 10 GHz for a pulse time-scale ≲0.5 s. Methods for improving this limit are briefly described.

An automated system for the detection of bursts of cosmic origin at radio frequencies has been built at Medicina (Bologna). The station, completely independent, is part of a network of observatories based in Ireland, United Kingdom, Switzerland and Italy. The receiving apparatus, operating at 151 and 408 MHz, and the experimental method used to reject unwanted events is described. Observational programmes include a search for the radio counterpart of X-and γ-ray bursts, observations of the galactic centre and Cygnus regions, and a full sky monitoring. Sensitivity limits as well as preliminary results are discussed.

Radio pulses from extensive air showers (EAS) have been observed with a 4 × 4 array of dipoles polarized E–W at a center frequency of 22.25 MHz and an effective bandwidth of 4 MHz. Observations were made simultaneously with antenna beams centered 30 °N and 30 °S of the zenith. The magnetic dip angle being 72°, the north beam faced across the geomagnetic field lines whereas the south beam faced along the field lines. In 600 hours of observation, 1 100 showers were recorded. Two 1-m2 plastic scintillators placed 30 m apart, in coincidence, triggered the cathode-ray-oscillograph recording system.Traces were scanned for 1 μs on either side of the expected location of the radio signals. Background levels were determined by scanning an interval of 0.75 μs, 3.5 μs after the beginning of the trace. Pulses were recorded on both antenna beams. Those on the north-pointing antenna were, on the average, twice as large as those on the south-pointing one. The results suggest that while charge separation in the earth's field is more important than charge excess in generating showers, it is not dominant.