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We present post process neutron capture computations for Asymptotic Giant Branch stars of 1.5 to 3 Mo and metallicities -1.3 to 0.1. The reference stellar models are computed with the FRANEC code, using the Schwarzschild's criterion for convection. Motivations for this choice are outlined. We assume that MHD processes induce the penetration of protons below the convective boundary, when the third dredge up occurs. There, the 13C(alpha,n)16O neutron source can subsequently operate, merging its effects with those of the 22Ne(alpha,n)25Mg reaction, activated at the temperature peaks characterizing AGB stages. This work has three main scopes. i) We provide a grid of abundance yields, as produced through our MHD mixing scheme, uniformly sampled in mass and metallicity. From it, we deduce that the solar s process distribution, as well as the abundances in recent stellar populations, can be accounted for, without the need of the extra primary like contributions suggested in the past. ii) We formulate analytical expressions for the mass of the 13C pockets generated, in order to allow easy verification of our findings. iii) We compare our results with observations of evolved stars and with isotopic ratios in presolar SiC grains, also noticing how some flux tubes should survive turbulent disruption, carrying C rich materials into the winds even when the envelope is O rich. This wind phase is approximated through the G component of AGB s processing. We conclude that MHD induced mixing is adequate to drive slow neutron capture phenomena accounting for observations. Our prescriptions should permit its inclusion into current stellar evolutionary codes., The Astrophysical Journal, submitted Sep. 2, 2020; accepted, Nov. 14, 2020. 23 pages, 23 figures

Many nearby AGNs display a significant short-term variability. In this work we re-analyze photometric data of four active galactic nuclei observed by Kepler in order to study the flickering activity, having as main goal that of searching for multiple components in the power density spectra. We find that all four objects have similar characteristics, with two break frequencies at approximately log(f/Hz)=-5.2 and -4.7. We consider some physical phenomena whose characteristic time-scales are consistent with those observed, in particular mass accretion fluctuations in the inner geometrically thick disc (hot X-ray corona) and unstable relativistic Rayleigh-Taylor modes. The former is supported by detection of the same break frequencies in the Swift X-ray data of ZW229-15. We also discuss rms-flux relations, and we detect a possible typical linear trend at lower flux levels. Our findings support the hypothesis of a multiplicative character of variability, in agreement with the propagating accretion fluctuation model.

Jets from Active Galactic Nuclei (AGN) inflate large cavities in the hot gas environment around galaxies and galaxy clusters. The large-scale gas circulation promoted within such cavities by the jet itself gives rise to backflows that propagate back to the center of the jet-cocoon system, spanning all the physical scales relevant for the AGN. Using an Adaptive Mesh Refinement code, we study these backflows through a series of numerical experiments, aiming at understanding how their global properties depend on jet parameters. We are able to characterize their mass flux down to a scale of a few kiloparsecs to about $0.5\,\mathrm{M_\odot/y}$for as long as $15$ or $20$ Myr, depending on jet power. We find that backflows are both spatially coherent and temporally textbf{intermittent}, independently of jet power in the range $10^{43-45}$ erg/s. Using the mass flux thus measured, we model analytically the effect of backflows on the central accretion region, where a Magnetically Arrested Disk lies at the center of a thin circumnuclear disk. Backflow accretion onto the disk modifies its density profile, producing a flat core and tail. We use this analytic model to predict how accretion beyond the BH magnetopause is modified, and thus how the jet power is temporally modulated. Under the assumption that the magnetic flux stays frozen in the accreting matter, and that the jets are always launched via the Blandford-Znajek (1977) mechanism, we find that backflows are capable of boosting the jet power up to tenfold during relatively short time episodes (a few Myr).

We perform relativistic hydrodynamic simulations of the formation and evolution of AGN cocoons produced by very light powerful jets. We calculate the intensity maps of the Sunyaev-Zel'dovich (SZ) effect at high frequencies for the simulated AGN cocoons using the relativistically correct Wright formalism. Our fully relativistic calculations demonstrate that the contribution from the high temperature gas (kb Te ~ 100 keV) to the SZ signal from AGN cocoons at high frequencies is stronger than that from the shocked ambient intercluster medium owing to the fact that the relativistic spectral functions peak at these temperature values. We present simulations of the SZ effect from AGN cocoons at various frequencies, and demonstrate that SZ observations at 217 GHz and at higher frequencies, such as 857 GHz, will provide us with knowledge about the dynamically-dominant component of AGN cocoons.

We present recent Hubble Space Telescope observations of the inner filament of Centaurus A, using the new Wide Field Camera 3 (WFC3) $F225W, F657N$ and $F814W$ filters. We find a young stellar population near the south-west tip of the filament. Combining the WFC3 dataset with archival Advanced Camera for Surveys (ACS) $F606W$ observations, we are able to constrain the ages of these stars to

The age and metallicity gradients for a sample of group and cluster galaxies from N-body+hydrodynamical simulation are analysed in terms of galaxy stellar mass. Dwarf galaxies show null age gradient with a tail of high and positive values for systems in groups and cluster outskirts. Massive systems have generally zero-age gradients which turn to positive for the most massive ones. Metallicity gradients are distributed around zero in dwarf galaxies and become more negative with mass; massive galaxies have steeper negative metallicity gradients, but the trend flattens with mass. In particular, fossil groups are characterized by a tighter distribution of both age and metallicity gradients. We find a good agreement with both local observations and independent simulations. Interestingly, our results suggest that environment differently affects the gradients at low and high masses. The results are also discussed in terms of the central age and metallicity, as well as the total colour, specific star formation and velocity dispersion.

13 citations (as of 21/10/2020) Aims: We test the effects of re-orienting jets from an active galactic nucleus (AGN) on the intracluster medium in a galaxy cluster environment with short central cooling time. We investigate both the appearance and the properties of the resulting cavities, and the efficiency of the jets in providing near-isotropic heating to the cooling cluster core. Methods: We use numerical simulations to explore four models of AGN jets over several active/inactive cycles. We keep the jet power and duration fixed across the models, varying only the jet re-orientation angle prescription. We track the total energy of the intracluster medium (ICM) in the cluster core over time, and the fraction of the jet energy transferred to the ICM. We pay particular attention to where the energy is deposited. We also generate synthetic X-ray images of the simulated cluster and compare them qualitatively to actual observations. Results: Jets whose re-orientation is minimal (≲20°) typically produce conical structures of interconnected cavities, with the opening angle of the cones being 15-20°, extending to 300 kpc from the cluster centre. Such jets transfer about 60% of their energy to the ICM, yet they are not very efficient at heating the cluster core, and even less efficient at heating it isotropically, because the jet energy is deposited further out. Jets that re-orientate by ≳20° generally produce multiple pairs of detached cavities. Although smaller, these cavities are inflated within the central 50 kpc and are more isotropically distributed, resulting in more effective heating of the core. Such jets, over hundreds of millions of years, can deposit up to 80% of their energy precisely where it is required. Consequently, these models come the closest in terms of approaching a heating/cooling balance and mitigating runaway cooling of the cluster core even though all models have identical jet power/duration profiles. Additionally, the corresponding synthetic X-ray images exhibit structures and features closely resembling those seen in real cool-core clusters. The movies associated to Figs. 1-4 are available at http://https://www.aanda.org/

(Abridged) We apply a very general statistical theorem introduced by Cramer (1936) to study the origin of the deviations of the halo spin PDF from the reference lognormal shape. We find that these deviations originate from correlations between two quantities entering the definition of spin, namely the ratio $J/M^{5/2}$ (which depends only on mass) and the total gravitational binding energy $E$. To reach this conclusion, we have made usage of the results deduced from two high spatial- and mass resolution simulations. Our simulations cover a relatively small volume and produce a sample of more than 16.000 gravitationally bound halos, each traced by at least 300 particles. We verify that our results are stable to different systematics, by comparing our results with those derived by the GIF2 and by a more recent simulation performed by Maccio' et al. We find that the spin probability distribution function shows systematic deviations from a lognormal, at all redshifts z

By means of our own cosmological-hydrodynamical simulation and semi-analytical model we studied galaxy population properties in clusters and groups, spanning over 10 different bands from UV to NIR, and their evolution since redshift z=2. We compare our results in terms of galaxy red/blue fractions and luminous-to-faint ratio (LFR) on the Red Sequence (RS) with recent observational data reaching beyond z=1.5. Different selection criteria were tested in order to retrieve galaxies belonging to the RS: either by their quiescence degree measured from their specific SFR ("Dead Sequence"), or by their position in a colour-colour plane which is also a function of sSFR. In both cases, the colour cut and the limiting magnitude threshold were let evolving with redshift, in order to follow the natural shift of the characteristic luminosity in the LF. We find that the Butcher-Oemler effect is wavelength-dependent, with the fraction of blue galaxies increasing steeper in optical colours than in NIR. Besides, only when applying a lower limit in terms of fixed absolute magnitude, a steep BO effect can be reproduced, while the blue fraction results less evolving when selecting samples by stellar mass or an evolving magnitude limit. We then find that also the RS-LFR behaviour, highly debated in the literature, is strongly dependent on the galaxy selection function: in particular its very mild evolution recovered when measured in terms of stellar mass, is in agreement with values reported for some of the highest redshift confirmed (proto)clusters. As to differences through environments, we find that normal groups and (to a lesser extent) cluster outskirts present the highest values of both star forming fraction and LFR at low z, while fossil groups and cluster cores the lowest: this separation among groups begins after z~0.5, while earlier all group star forming properties are undistinguishable., revised version, A&A accepted (11 pages, 6 figures)

Clustering analysis is one of multivariate data analysis techniques which allows to gather statistical data units into groups, in order to minimize the logical distance within each group and to maximize the one between different groups. In these proceedings, the authors present a novel approach to the muontomography data analysis based on clustering algorithms. As a case study we present the Muon Portal project that aims to build and operate a dedicated particle detector for the inspection of harbor containers to hinder the smuggling of nuclear materials. Clustering techniques, working directly on scattering points, help to detect the presence of suspicious items inside the container, acting, as it will be shown, as a filter for a preliminary analysis of the data.

We have performed a series of N-body/hydrodynamical (TreeSPH) simulations of clusters and groups of galaxies, selected from cosmological N-body simulations within a $\Lambda$CDM framework: these objects have been re-simulated at higher resolution to $z$=0, in order to follow also the dynamical, thermal and chemical input on to the ICM from stellar populations within galaxies. The simulations include metal dependent radiative cooling, star formation according to different IMFs, energy feedback as strong starburst-driven galactic super-winds, chemical evolution with non-instantaneous recycling of gas and heavy elements, effects of a meta-galactic UV field and thermal conduction in the ICM. In this Paper I of a series of three, we derive results, mainly at $z=0$, on the temperature and entropy profiles of the ICM, its X-ray luminosity, the cluster cold components (cold fraction as well as mass--to--light ratio) and the metal distribution between ICM and stars. In general, models with efficient super-winds, along with a top-heavy stellar IMF, are able to reproduce fairly well the observed $L_X-T$ relation, the entropy profiles and the cold fraction. Observed radial ICM temperature profiles can be matched, except for the gradual decline in temperature inside of $r\sim$~0.1$R_{\rm{vir}}$. Metal enrichment of the ICM gives rise to somewhat steep inner iron gradients; yet, the global level of enrichment compares well to observational estimates after correcting for the stars formed at late times at the base of the cooling flows; also the metal partition between stars and ICM gets into good agreement with observations., Comment: 23 pages, 20 colour figures; final version accepted

FLY is a parallel treecode which makes heavy use of the one-sided communication paradigm to handle the management of the tree structure. In its public version the code implements the equations for cosmological evolution, and can be run for different cosmological models. This reference guide describes the actual implementation of the algorithms of the public version of FLY, and suggests how to modify them to implement other types of equations (for instance the Newtonian ones)

N-body codes to perform simulations of the origin and evolution of the Large Scale Structure of the Universe have improved significantly over the past decade both in terms of the resolution achieved and of reduction of the CPU time. However, state-of-the-art N-body codes hardly allow one to deal with particle numbers larger than a few 10^7, even on the largest parallel systems. In order to allow simulations with larger resolution, we have first re-considered the grouping strategy as described in Barnes (1990) (hereafter B90) and applied it with some modifications to our WDSH-PT (Work and Data SHaring - Parallel Tree) code. In the first part of this paper we will give a short description of the code adopting the Barnes and Hut algorithm \cite{barh86} (hereafter BH), and in particular of the memory and work distribution strategy applied to describe the {\it data distribution} on a CC-NUMA machine like the CRAY-T3E system. In the second part of the paper we describe the modification to the Barnes grouping strategy we have devised to improve the performance of the WDSH-PT code. We will use the property that nearby particles have similar interaction list. This idea has been checked in B90, where an interaction list is builded which applies everywhere within a cell C_{group} containing a little number of particles N_{crit}. B90 reuses this interaction list for each particle $ p \in C_{group}$ in the cell in turn. We will assume each particle p to have the same interaction list. Thus it has been possible to reduce the CPU time increasing the performances. This leads us to run simulations with a large number of particles (N ~ 10^7/10^9) in non-prohibitive times., Comment: 13 pages and 7 Figures

Evidence of clustering within the Coma Cluster is found by means of a multiscale analysis of the combined angular-redshift distribution. We have compiled a catalog of 798 galaxy redshifts from published surveys of the region of the Coma Cluster. We examine the presence of substructure and of voids at different scales ranging from ∼1 to ∼16 h-1 Mpc, using subsamples of the catalog ranging from cz = 3000 km s-1 to cz = 28,000 km s-1. Our substructure detection method is based on the wavelet transform and on segmentation analysis. The wavelet transform allows us to find structures at different scales, and the segmentation method allows a quantitative statistical and morphological analysis of the sample. From the whole catalog, we select a subset of 320 galaxies, with redshifts between cz = 5858 km s-1 and cz = 8168 km s-1, which we identify as belonging to the central region of Coma and upon which we have performed a deeper analysis, on scales ranging from 180 h-1 kpc to 1.44 h-1 Mpc. Our results are expressed in terms of the number of structures or voids and their sphericity for different values of the threshold detection and at all the scales investigated. According to our analysis, there is strong evidence of multiple hierarchical substructure, on scales ranging from a few hundreds of kilo-parsecs to about 4 h-1 Mpc. The morphology of these substructures is rather spherical. On a scale of 720 h-1 kpc we find two main subclusters that have been found before, but our wavelet analysis shows even more substructures, whose redshift position is approximately marked by the following bright galaxies: NGC 4934 and 4840, NGC 4889, NGC 4898 and 4864, NGC 4874 and 4839, NGC 4927, and NGC 4875.

We reconsider the problem of the age of the stellar disks of late-type low surface brightness galaxies (LSBs) by making use of a new IMF recently derived from numerical fluid dynamics simulations (Padoan, Nordlund, & Jones 1997), and a new synthetic stellar population code, based on Jimenez & MacDonald (1997) evolutionary tracks and Kurucz atmospheric models (Kurucz 1992). We find that the disks of LSBs are not necessarily formed very recently. Their colors seem to indicate that the disks of LSBs started to form stars at least 7 Gyr ago, and more likely about 9 Gyr ago, and therefore contrary to what has been claimed in the literature disks of LSBs are not young.

We investigate the interplay between jets from Active Galactic Nuclei (AGNs) and the surrounding InterStellar Medium (ISM) through full 3D, high resolution, Adaptive Mesh Refinement simulations performed with the FLASH code. We follow the jet- ISM system for several Myr in its transition from an early, compact source to an extended one including a large cocoon. During the jet evolution, we identify three major evolutionary stages and we find that, contrary to the prediction of popular theoretical models, none of the simulations shows a self-similar behavior. We also follow the evolution of the energy budget, and find that the fraction of input power deposited into the ISM (the AGN coupling constant) is of order of a few percent during the first few Myr. This is in broad agreement with galaxy formation models employing AGN feedback. However, we find that in these early stages, this energy is deposited only in a small fraction (< 1%) of the total ISM volume. Finally we demonstrate the relevance of backflows arising within the extended cocoon generated by a relativistic AGN jet within the ISM of its host galaxy, previously proposed as a mechanism for self-regulating the gas accretion onto the central object. These backflows tend later to be destabilized by the 3D dynamics, rather than by hydrodynamic (Kelvin- Helmholtz) instabilities. Yet, in the first few hundred thousand years, backflows may create a central accretion region of significant extent, and convey there as much as a few millions of solar masses., Accepted in MNRAS - 16 pages, 12 figures - Multimedia available on the author's webpage: http://www.mpia.de/~cielo

In recent years an increasing interest has grown within the international community towards the prevention of terroristic threatenings. This traffic requires a broader international control and it becomes necessary to enhance systems for borders security. Currently, muon tomography is under study to be used as an experimental technique to be implemented in devices able to perform an efficient scanning to detect radioactive materials inside different kind of systems, like shipping containers or cargos, for borders control. In this paper the authors will focus on the automated identification and visualization of illicit materials inside cargo containers in the context of the Muon Portal project. The track reconstruction is a challenging task and consists in the elaboration of data from the detector planes in order to obtain information on the deflection occurred by the muons within the volume scanned. Latest results of different reconstruction algorithms, such as the well known POCA and the EM-Likelihood, are presented and discussed together with the novel application of clustering algorithms to the data analysis. The usage of these techniques allows to infer the implicit information in the data and clustering algorithms make the tracks reconstruction and the visualization of the containers content be independent from the grid and the 3D-voxels, acting as a filter for a preliminary analysis of the data.

Muon tomographic visualization techniques try to reconstruct a 3D image as close as possible to the real localization of the objects being probed. Statistical algorithms under test for the reconstruction of muon tomographic images in the Muon Portal Project are here discussed. Autocorrelation analysis and clustering algorithms have been employed within the context of methods based on the Point Of Closest Approach (POCA) reconstruction tool. An iterative method based on the log-likelihood approach was also implemented. Relative merits of all such methods are discussed, with reference to full Geant4 simulations of different scenarios, incorporating medium and high-Z objects inside a container., Comment: 12 pages, 8 figures

We describe a new parallel N-body code for cosmological simulations. The code is based on a work- and data sharing scheme, and is implemented within the Cray Research Corporation's CRAFT programming environment. Different data distribution schemes have been adopted for bodies' and tree's structures. Tests performed for two different types of initial distributions show that the performance scales almost ideally as a function of the size of the system and of the number of processors. We discuss the factors affecting the absolute speedup and how it can be increased with a better tree's data distribution scheme., 16 pages, 8 figures. Uses elsart.sty and epsf.sty. Accepted for publication in Computer Physics Communications

The hypervelocity OB stars in the Milky Way Galaxy were ejected from the central regions some 10-100 million years ago. We argue that these stars, {as well as many more abundant bound OB stars in the innermost few parsecs,} were generated by the interactions of an AGN jet from the central black hole with a dense molecular cloud. Considerations of the associated energy and momentum injection have broader implications for the possible origin of the Fermi bubbles and for the enrichment of the intergalactic medium., Comment: 4 pages, 1 figure. Astronomy and Astrophysics Letters, in press

While new infrastructures for large computational challenges begin to be widely accessible to researchers, computational codes need to be re-designed to exploit new facilities. The Grid and the cloud computing concepts are changing the computational resource distribution and availability, and much effort start to be made to develop new codes for a better exploitation of new resources. This paper presents an example of the use of Grid resources, based on gLite middleware, to run cosmological simulations, that, up to now, are normally executed on Supercomputers. We have also used the Grid to explore and visualize the dataset. We discuss non particular the performance of FLY a parallel code implementing the octal-tree algorithm introduced by J. Barnes and P. Hut to compute the gravitational field efficiently. It simulates the evolution of the collisionless component of the material content of our Universe. FLY was originally developed to run on mainframe systems using the one-side communication paradigm, but we are now presenting a modified version of the computational algorithm to exploit the Grid environment. We also integrated the data exploration and visualization process on the Grid, to obtain preliminary results using the distributed facilities.

Models of the formation, evolution and structure of the solar cylinder are constructed on the basis of a large set of observational data on mainly late-type stars. Star formation in the disc is modelled with a simple, phenomenological prescription of the Schmidt type: Σ#78 * ∞Σ g N , N = 1-2. Models with a threshold for star formation are also considered. Infall of halo gas is assumed to happen on a characteristic time-scale t i . The results obtained are largely independent of the star formation prescription. For the best-fitting model (N = 1), we find that the age of the solar cylinder is t 0 = 11.8 ± 1.0 Gyr and that t i = 3.4 ± 0.4 Gyr

Part I. AGNs, Starbursts and Galaxy Evolution: 1. The effect of mass and star-formation timescale on galaxy evolution C. Harrison and M. Colless 2. Suppressing cluster cooling flows by multiple AGN activity A. Nusser 3. Starbursts and AGN activity in Spitzer-selected sources at high-z M. Polletta, A. Omont, C. Lonsdale and D. Shupe 4. Star formation in galaxies hosting active galactic nuclei up to z~1 J. Silverman Part II. Coevolution of Black Holes and Galaxies: 5. The symbiosis between galaxies and SMBHs G. L. Granato, M. Cook, A. Lapi and L. Silva 6. On the origin of halo assembly bias A. Keselman 7. AGN, downsizing and galaxy bimodality M. J. Stringer, A. J. Benson, K. Bundy and R. S. Ellis Part III. Outflows and Radio Galaxies: 8. Interaction and gas outflows in radio-loud AGN - disruptive and constructive effects of radio jets R. Morganti 9. Young radio sources: evolution and broad-band emission L. Ostorero, R. Moderski, L. Stawarz, M. Begelman, A. Diaferio, I. Kowalska, J. Kataoka and S. J. Wagner 10. The duty cycle of radio galaxies and AGN feedback S. Shabala 11. Environments or outflows? New insights into the origin of narrow associated QSO absorbers V. Wild Part IV. Models and Numerical Simulations: Methods and Results: 12. Physical models of AGN feedback V. Antonuccio-Delogu, J. Silk, C. Tortora, S. Kaviraj, N. Napolitano and A. D. Romeo 13. Large scale expansion of AGN outflows in a cosmological environment P. Barai 14. Relativistic jets and the inhomogeneous interstellar medium Geoffrey V. Bicknell, Jackie L. Cooper and Ralph S. Sutherland 15. AGN feedback effect on intracluster medium properties from galaxy clusters hydrodynamical simulations D. Fabjan, S. Borgani, L. Tornatore, A. Saro and K. Dolag 16. Physics and fate of jet-related emission line regions M. Krause and V. Gaibler 17. Cusp-core dichotomy of ellitpical galaxies: the role of thermal evaporation C. Nipoti.

We study the internal circulation within the cocoon carved out by the relativistic jet emanating from an active galactic nucleus (AGN) within the interstellar medium (ISM) of its host galaxy. First, we develop a model for the origin of the internal flow, noticing that a significant increase of large-scale velocity circulation within the cocoon arises as significant gradients in the density and entropy are created near the hotspot (a consequence of Crocco's vorticity generation theorem). We find simple and accurate approximate solutions for the large-scale flow, showing that a backflow towards the few inner parsec region develops. We solve the appropriate fluid dynamic equations, and we use these solutions to predict the mass inflow rates towards the central regions. We then perform a series of 2D simulations of the propagation of jets using FLASH 2.5, in order to validate the predictions of our model. In these simulations, we vary the mechanical input power between 10 43 and 10 45 erg s -1 , and assume a Navarro-Frenk-White (NFW) density profile for the dark matter halo, within which an isothermal diffuse ISM is embedded. The backflows which arise supply the central AGN region with very low angular-momentum gas, at average rates of the order of 0.1-0.8 M ⊙ yr -1 , the exact value seen to be strongly dependent on the central ISM density (for fixed input jet power). The time-scales of these inflows are apparently weakly dependent on the jet/ISM parameters, and are of the order of 3-5 x 10 7 yr. We then argue that these backflows could (at least partially) feed the AGN, and provide a self-regulatory mechanism of AGN activity, that is not directly controlled by, but instead controls, the star formation rate within the central circumnuclear disc.

Aims. The Large Binocular Cameras (LBC) are two twin wide field cameras (FOV ~ 23'x 25') mounted at the prime foci of the 8.4m Large Binocular Telescope (LBT). We performed a weak lensing analysis of the z=0.288 cluster Abell 611 on g-band data obtained by the blue-optimized Large Binocular Camera in order to estimate the cluster mass. Methods. Due to the complexity of the PSF of LBC, we decided to use two different approaches, KSB and Shapelets, to measure the shape of background galaxies and to derive the shear signal produced by the cluster. Then we estimated the cluster mass with both aperture densitometry and parametric model fits. Results. The combination of the large aperture of the telescope and the wide field of view allowed us to map a region well beyond the expected virial radius of the cluster and to get a high surface density of background galaxies (23 galaxies/arcmin^2). This made possible to estimate an accurate mass for Abell 611. We find that the mass within 1.5 Mpc is: $(8\pm3)\times 10^{14} M_\odot$ from the aperture mass technique and $(5\pm1)\times 10^{14} M_\odot$ using the model fitting by a NFW mass density profile, for both Shapelets and KSB methods. This analysis demonstrates that LBC is a powerful instrument for weak gravitational lensing studies., 13 pages, 15 figures. Accepted for publication in Astronomy and Astrophysics

We study the feedback from an AGN on stellar formation within its host galaxy, mainly using one high resolution numerical simulation of the jet propagation within the interstellar medium of an early-type galaxy. In particular, we show that in a realistic simulation where the jet propagates into a two-phase ISM, star formation can initially be slightly enhanced and then, on timescales of few million years, rapidly quenched, as a consequence both of the high temperatures attained and of the reduction of cloud mass (mainly due to Kelvin-Helmholtz instabilities). We then introduce a model of (prevalently) {\em negative} AGN feedback, where an exponentially declining star formation is quenched, on a very short time scale, at a time t_AGN, due to AGN feedback. Using the Bruzual & Charlot (2003) population synthesis model and our star formation history, we predict galaxy colours from this model and match them to a sample of nearby early-type galaxies showing signs of recent episodes of star formation (Kaviraj et al. 2007). We find that the quantity t_gal - t_AGN, where t_gal is the galaxy age, is an excellent indicator of the presence of feedback processes, and peaks significantly around t_gal - t_AGN \approx 0.85 Gyr for our sample, consistent with feedback from recent energy injection by AGNs in relatively bright (M_{B} \lsim -19) and massive nearby early-type galaxies. Galaxies that have experienced this recent feedback show an enhancement of 3 magnitudes in NUV(GALEX)-g, with respect to the unperturbed, no-feedback evolution. Hence they can be easily identified in large combined near UV-optical surveys., 18 pages, 16 figures, accepted for publication on MNRAS. This version includes revisions after the referee's report

N-body + hydrodynamical simulations of the formation and evolution of galaxy groups and clusters in a LambdaCDM cosmology are used in order to follow the building-up of the colour-magnitude relation in two clusters and in 12 groups. We have found that galaxies, starting from the more massive, move to the Red Sequence (RS) as they get aged over times and eventually set upon a ``dead sequence'' (DS) once they have stopped their bulk star formation activity. Fainter galaxies keep having significant star formation out to very recent epochs and lie broader around the RS. Environment plays a role as galaxies in groups and cluster outskirts hold star formation activity longer than the central cluster regions. However galaxies experiencing infall from the outskirts to the central parts keep star formation on until they settle on to the DS of the core galaxies. Merging contributes to mass assembly until z~1, after which major events only involve the brightest cluster galaxies. The emerging scenario is that the evolution of the colour-magnitude properties of galaxies within the hierarchical framework is mainly driven by star formation activity during dark matter halos assembly. Galaxies progressively quenching their star formation settle to a very sharp ``red and dead'' sequence, which turns out to be universal, its slope and scatter being almost independent of the redshift (since at least z~1.5) and environment. Differently from the DS, the operatively defined RS evolves more evidently with z, the epoch when it changes its slope being closely corresponding to that at which the passive galaxies population takes over the star forming one: this goes from z~1 in clusters down to 0.4 in normal groups., MNRAS in press

Recently, R. Cen (2006) has suggested that small protogalactic halos at high redshift (z ' 20− 25) could be surrounded by extended (r ≈ 1h−1Mpc) gaseous halos, which could be marginally detected by LOFAR. However, more recent work on the mass function at high z shows that these estimates could be too optimistic. Moreover, the variance over the sky of this signal could be very large, thus undermining the practical usage of these halos for the determination of cosmological parameters using weak lensing.

Cosmological simulations of structures and galaxies formations have played a fundamental role in the study of the origin, formation and evolution of the Universe. These studies improved enormously with the use of supercomputers and parallel systems and, recently, grid based systems and Linux clusters. Now we present the new version of the tree N-body parallel code FLY that runs on a PC Linux Cluster using the one side communication paradigm MPI-2 and we show the performances obtained. FLY is included in the Computer Physics Communication Program Library. This new version was developed using the Linux Cluster of CINECA, an IBM Cluster with 1024 Intel Xeon Pentium IV 3.0 Ghz. The results show that it is possible to run a 64 Million particle simulation in less than 15 minutes for each timestep, and the code scalability with the number of processors is achieved. This lead us to propose FLY as a code to run very large N-Body simulations with more than $10^{9}$ particles with the higher resolution of a pure tree code. The FLY new version will be available at http://www.ct.astro.it/fly/ and CPC Program Library., Comment: 15 pages, 5 figures

Weak lensing applied to deep optical images of clusters of galaxies provides a powerful tool to reconstruct the distribution of the gravitating mass associated to these structures. We use the shear signal extracted by an analysis of deep exposures of a region centered around the galaxy cluster Abell 209, at redshift z=0.2, to derive both a map of the projected mass distribution and an estimate of the total mass within a characteristic radius. We use a series of deep archival R-band images from CFHT-12k, covering an area of 0.3 deg^2. We determine the shear of background galaxy images using a new implementation of the modified Kaiser-Squires-Broadhurst pipeline for shear determination, which we has been tested against the ``Shear TEsting Program 1 and 2'' simulations. We use mass aperture statistics to produce maps of the 2 dimensional density distribution, and parametric fits using both Navarro-Frenk-White (NFW) and singular-isothermal-sphere profiles to constrain the total mass. The projected mass distribution shows a pronounced asymmetry, with an elongated structure extending from the SE to the NW. This is in general agreement with the optical distribution previously found by other authors. A similar elongation was previously detected in the X-ray emission map, and in the distribution of galaxy colours. The circular NFW mass profile fit gives a total mass of M_{200} = 7.7^{+4.3}_{-2.7} 10^{14} solar masses inside the virial radius r_{200} = 1.8\pm 0.3 Mpc. The weak lensing profile reinforces the evidence for an elongated structure of Abell 209, as previously suggested by studies of the galaxy distribution and velocities., Comment: accepted by A&A, 15 pages, 11 figures

X-ray spectroscopy of the hot Intergalactic Medium (IGM) within Clusters of Galaxies has revealed that a significant enrichment has occurred during their evolution. The astrophysical mechanisms which have driven this enrichment have not however been quantitatively clarified yet. In this contribution we shortly review the present-day knowledge of clusters' chemical abundances and we discuss how future x-ray missions, notably SPECTRUM-RONTGEN-GAMMA, ASCA and XMM, could contribute to extend our knowledge to redshifts larger than z ≈ 0.4.

AstroMD is a visualization software offering several capabilities specifically oriented to the cosmological analysis of three-dimensional structures. It was developed within the framework of the Cosmo.Lab project, financially supported by the European Community, which involves several European Astrophysical Institutions and the CINECA. This tool gives a 3D graphic representation of data, exploiting the most advanced visualization technology based on virtual reality, and has several built-in-tools which allow the user an efficient manipulation and analysis of data, in order to build a leading edge instrument for scientific research. It was developed using the Visualization Toolkit (VTK) by Kitware, a freely available visualization library portable on many platforms. AstroMD is an open source freely available code at the address http://cosmolab.cineca.it/.

The AstroMD toolkit is a visualization and analysis software, specifically oriented to astrophysical data representation. It is included in the project Cosmo.Lab, financed by the European Community, which involves several European astrophysical institutions and CINECA. This tool gives a 3D graphic representation of the data exploiting all the available information and making use of the immersive visualization techniques. AstroMD uses the most advanced visualization technology, based on virtual reality, in order to build a leading edge instrument both for scientific research and for cultural dissemination and education. It is developed using the Visualization Toolkit (VTK) by Kitware (http://www.kitware.com), a freely available visualization library portable on several platforms. AstroMD is an open source completely free code which is freely available (http://cosmolab.cineca.it).

We use the results of a high resolution N-body simulation to investigate the role of the environment on the formation and evolution of galaxy-sized halos. Starting from a set of constrained initial conditions, we have produced a final configuration hosting a double cluster in one octant and a large void extending over two octants of the simulation box. We present results for two statistics: the relationship between 1-D velocity dispersion and mass and the probability distribution of the spin parameter $P(\lambda)$. The \svm relationship is well reproduced by the Truncated Isothermal Sphere (TIS) model introduced by Shapiro et al. (1999), although the slope is different from the original prediction. A series of \svm relationships for different values of the anisotropy parameter $\beta$, obtained using the theoretical predictions by Lokas and Mamon (2001) for NFW density profiles are found to be only marginally consistent with the data. Using some properties of the equilibrium TIS models, we construct subsamples of {\em fiducial} equilibrium TIS halos from each of the three subregions, and we study their properties. For these halos, we do find an environmental dependence of their properties, in particular of the spin parameter distribution $P(\lambda)$. We study in more detail the TIS model, and we find new relationships between the truncation radius and other structural parameters. No gravitationally bound halo is found having a radius larger than the critical value for gravithermal instability for TIS halos (\rt $\ge 34.2 r_{0}$, where $r_{0}$ is the core radius of the TIS solution). We do however find a dependence of this relationship on the environment, like for the $P(\lambda)$ statistics. These facts hint at a possible r\^{o}le of tidal fields at determining the statistical properties of halos., Comment: 12 pages, 14 figures. Accepted by MNRAS. Adopted an improved algorithm for halo finding and added a comparison with NFW models

We present and discuss a method to identify substructures in combined angular-redshift samples of galaxies within Clusters. The method relies on the use of Discrete Wavelet Transform (hereafter DWT) and has already been applied to the analysis of the Coma cluster (Gambera et al. 1997). The main new ingredient of our method with respect to previous studies lies in the fact that we make use of a 3D data set rather than a 2D. We test the method on mock cluster catalogs with spatially localized substructures and on a N-body simulation. Our main conclusion is that our method is able to identify the existing substructures provided that: a) the subclumps are detached in part or all of the phase space, b) one has a statistically significant number of redshifts, increasing as the distance decreases due to redshift distortions; c) one knows {\it a priori} the scale on which substructures are to be expected. We have found that to allow an accurate recovery we must have both a significant number of galaxies ($\approx 200$ for clusters at z$\geq 0.4$ or about 800 at z$\leq$ 0.4) and a limiting magnitude for completeness $m_B=16$. The only true limitation to our method seems to be the necessity of knowing {\it a priori} the scale on which the substructure is to be found. This is an intrinsic drawback of the method and no improvement in numerical codes based on this technique could make up for it.

We study the propagation of relativistic jets originating from AGNs within the Interstellar/Intergalactic Medium of their host galaxies, and use it to build a model for the suppression of stellar formation within the expanding cocoon., 2 pages, 3 figures. Poster presented at IAU Symp. no. 245 ("Formation and Evolution of Galaxy Bulges"), Oxford, July 16-20, 2007